Regular Friday tea meetings & Other talks


The full 2024 schedule can be found here


April 2024

April 26:  Missing molecular gas in the outflow of NGC5728 revealed by JWST   --  Noam Cisneros


April 19: The stellar mass - angular momentum relation (Fall relation) of star-forming galaxies at cosmic noon  --  Juan Espejo

I will present an integrated measurement of the stellar specific angular momentum $j_\star$ of 41 star-forming galaxies at $1.5<z<2.5$. The measurement is based on radial profiles inferred from near-IR \textit{HST} photometry and a joint multi-resolution kinematic modelling using integral field spectroscopy (IFS) data in seeing-limited and adaptive optics-assisted modes from KMOS, SINFONI, and OSIRIS. From the 26 systems identified as rotating disks we investigate the $j_\star$ \textit{vs} stellar mass $M_\star$ relation (Fall relation) in the form $j_\star\propto M_\star^{\beta}$ where we find a power-law slope $\beta=0.26\pm0.13$, which deviates significantly from the commonly adopted redshift zero relation $\beta=2/3\approx 0.67$. I will discuss the various possible explanations for this discrepancy with respect to previous studies and the possible implications.


April 12: All Hands Meeting


April 5:  Understanding supermassive black hole accretion with GRAVITY+ --  Jinyi Shangguan

The high spatial resolution of GRAVITY has been able to measure the broad-line region (BLR) structure and the supermassive black hole (BH) mass out to the cosmic noon. The enhanced sensitivity of GRAVITY+ will enable much more accurate measurements for a significantly large active galactic nuclei (AGN) sample. What astrophysical problems can we address with this powerful technique? How should we best prepare for future GRAVITY+ projects? In this tea talk, I plan to review the long-lasting puzzles of the AGN accretion disk and its radiation properties. Due to the complexity of general relativity and plasma physics, observational constraints are crucial to understanding the BH accretion. Many phenomenological models of accretion disk radiation have been actively developed, but their comparisons to the observation are not conclusive. The accurate BH mass and the BLR structure, in particular, the inclination and inner and outer radius, are the key observables to solve these puzzles. Simultaneous observations of UV/optical and X-ray spectra are crucial auxiliary data to maximize the scientific outcome of GRAVITY+ observations. Exercises should be done to understand the required accuracy of GRAVITY+ observations, and some can be done with our current data.


March 2024

March 21: 3D Visualization of MICADO  --  Noam Cisneros


March 15: From GRAVITY(+) towards a kilometers baseline, large telescope interferometer  --  Frank Eisenhauer

The last years have seen a revolution in optical/IR interferometry of exoplanets, young stellar objects, and black holes. The ongoing GRAVITY+ upgrade will soon boost optical interferometry to the next level, for ever higher sensitivity and contrast, and opening up the extragalactic sky for milli-arcsecond resolution interferometry. Here we will give an outlook on expanding optical interferometry to kilometer wide arrays, which will then be hundred to thousand times sharper than even the largest single dish telescopes.


March 9: New Constraints on Molecular Gas Outflows in Massive SFGs at Cosmic Noon --  Capucine Barfety

Feedback in the form of outflows is believed to be a key ingredient in galaxy evolution. In cosmic noon galaxies, outflows have mostly been detected - and extensively studied - in the ionised gas phase, only to reveal that ionised gas outflows alone cannot be responsible for the quenching of star formation in galaxies. It has therefore been surmised that the bulk of outflows are taking place in the molecular gas phase. However, molecular gas outflows are inherently harder to detect, and studies in the nearby Universe suggest that their velocities are lower than their ionised gas counterparts. In consequence, the vast majority of molecular gas outflows at cosmic noon have been detected in luminous AGNs and quasars. Capitalising on the IRAM/PHIBSS CO survey of a large sample of 175 massive star-forming galaxies at 0.5<z<2.6, we investigate the presence of molecular gas outflow signatures via broad CO line emission and through spectral stacking. As the latter technique allows us to reach SNR > 20, we use our results to constrain molecular gas outflow properties in our sample, and discuss the implications on observational searches for molecular gas outflows in the general star-forming galaxy population.


March 1:  Recovering the gas properties of protoplanetary disks with ALMA --  Nicolas Kurtovic


February 2024

February 23: Membrane mirrors for large space telescopes   --  Sebastian Rabien

I will report on the production and prototype test of a polymer based parabolic membrane mirror. This polymer membrane approach is very different from usual mirror production and polishing procedures, and could help to solve weight and packaging issues for space telescopes. Developed over the last years, the mirrors are grown by chemical vapor deposition on a rotating liquid inside a vacuum chamber. We have demonstrated the feasibility of the method, with the successful fabrication and active surface shaping of parabolic membrane mirror prototypes up to 30 cm in diameter, laying the groundwork for affordable large packable mirror systems.


February 9: The CRISTAL survey:  Resolving kinematics of typical main-sequence star-forming galaxies at 4 < z < 6   --  Lilian Lee

Kinematics studies at z ~ 1- 3 have established the prevalence (~70%) of regular rotating disks of star-forming galaxies. However, there is yet to be a consensus on when disks settled, as high-resolution resolved studies are only available for a few galaxies at z > 4. The ALMA large program, CRISTAL, targeted the [CII] line in a sample of 19+ massive star-forming galaxies at 4 < z < 6, providing an unprecedented clear view of the dynamical state of z > 4 star-forming galaxies. In this talk, I will present a resolved kinematic study of CRISTAL galaxies, using various criteria to classify galaxies as rotational-dominated disks, candidate mergers, and dispersion-dominated systems. Detailed rotation curves, kinematic modelling, and constraints on the mass budgets of the disks will also be discussed. These findings have important implications for understanding the build-up processes and cosmic evolution of disk turbulence of high-z galaxy populations.


February 2:  Global Dynamical Friction for Cored Galaxies --  Karamveer Kaur

Global dynamical theories have completely changed our understanding of stellar dynamics, by putting forth the importance of resonant interactions. These phenomena are applicable to a broad range of astrophysical scales from planetary systems and star clusters to galaxies and even galaxy clusters.  Firstly, I will discuss the novel global approach to dynamical friction in the context of low-mass galaxies. Classical dynamical friction theory relying on local interactions, overpredicts the strength of frictional torques in the background cored distribution of mass. Global interactions take into account real orbital structure of background distribution and relies on resonant encounters between the perturer and background "stars". In the innermost regions of the core, the global dynamical friction becomes highly suppressed that the further infall of perturber's orbit is effectively stalled. I will discuss this phenomenon of core stalling and its relevance for a variety of astrophysical systems, especially the low-mass galaxies, both dwarfs and ultra diffuse galaxies, abundant in old globular clusters. These systems are a perfect testing ground of these dynamical theories that can help probe the underlying mass distribution of the host dark matter halo. 


January 2024

January 26: Kinematics of Massive Strongly Lensed Galaxies and Memorable 3.33 Years at MPE   --  Daizhong Liu

I would like to first present the recent work of studying the cold gas and ionized gas kinematics with ALMA and ERIS in a hyperluminous, strongly lensed Einstein ring galaxy at z~2. In this work, thanks to the sensitivity of ERIS and the high-resolution of ALMA, the Einstein ring’s velocity and velocity dispersion are well modeled by our kinematic tool DysmalPy. We reveal a massive, rotating and starbursting disk representing an extreme case of z~2 galaxies, but it seems to be not triggered by major mergers. Instead, massive turbulent disk is possible for triggering the high total star formation rate (>1000 Msun/yr) in the disk. Then, I would like to express my thanks to the group here, for my 3 years and 4 months of post-doc time immersed in brilliant science and unparalleled instrumental development here. Thank you!


January 19:  Probing the planet-forming zones of protoplanetary disks: the power of mid-infrared spectroscopy --  Stavros Pastras

Protoplanetary disks provide the material and environment for planet formation. With over 5000 known exoplanets, it is essential to study the conditions in protoplanetary disks and how they evolve in order to explain the rich diversity of planetary architectures and compositions. Most planets are expected to form in the inner few au of disks, a region that is accessible via mid-infrared (MIR) observations. With MIR spectroscopy, we can probe the inner disk structure and composition using high spectral resolution observations from the ground and large spectral coverage observations from space. In this talk, I will present observations from VLT-CRIRES+ and JWST-MIRI, highlighting the power of each in uncovering the conditions, composition, and evolution of the inner regions of protoplanetary disks. Finally, I will discuss my plans for the coming years, in particular my efforts to push these observations to disks around lower-mass stars.


December 2023

December 15:  All Hands Meeting 


December 8: MICADO @ MPE - Overview, status, and outlook   --  Eckhard Sturm


December 1:  Probing the planet-forming zones of protoplanetary disks: the power of mid-infrared spectroscopy --  Sierra Grant

Protoplanetary disks provide the material and environment for planet formation. With over 5000 known exoplanets, it is essential to study the conditions in protoplanetary disks and how they evolve in order to explain the rich diversity of planetary architectures and compositions. Most planets are expected to form in the inner few au of disks, a region that is accessible via mid-infrared (MIR) observations. With MIR spectroscopy, we can probe the inner disk structure and composition using high spectral resolution observations from the ground and large spectral coverage observations from space. In this talk, I will present observations from VLT-CRIRES+ and JWST-MIRI, highlighting the power of each in uncovering the conditions, composition, and evolution of the inner regions of protoplanetary disks. Finally, I will discuss my plans for the coming years, in particular my efforts to push these observations to disks around lower-mass stars.


November 2023

November 24:  The complexity of MICADO, together with high demanding requirements, underscores the necessity for an accurate test campaign down to component level. --  Federico Biondi

The Pilot Mirror is the flat folding mirror that a light ray entering the MICADO cryostat first encounters, and is a good example of a component that requires careful characterization given its impact on the overall optical quality of the instrument.
The mirror was manufactured and characterized in warm conditions at the Fraunhofer IOF in summer 2023, and delivered to MPE last August. We are currently testing it in our laboratory, reproducing the operational environment of 82 K, and its mechanical coupling to an aluminum frame. The objective of the test is to evaluate the impact of the material deformation on its surface quality, when subjected to a thermal load of ~214 K. The ultimate goal is to verify the compliance with the 14 nm RMS / 70 nm PV requirements for its surface quality.
For our tea talk, I have prepared a description of the setup and of the initial results. I will outline some lessons learned, potentially useful for other lab users, and the impact of this test on the MAIT strategy at sub-system level.


November 17: The specific angular momentum of ETGs and its relation with stellar mass --  Claudia Pulsoni

Mass and angular momentum (AM) are key parameters to understand galaxies. Their co-evolution establishes a tight relation between the stellar specific AM (j∗) and the total stellar mass (M∗) for disk galaxies. The case of massive early type galaxies (ETGs) is far less explored, as a large fraction of their AM is distributed at large radii where stellar spectroscopy is unfeasible.
In this talk, I present results for 32 nearby ETGs based on 2D kinematics out to a mean 6 effective radii. The results show that, once j* is integrated out to large radii, ETGs contain even less AM than previously found. This is a factor of 9 lower compared to spirals with similar M* (and up to a factor 13 when including IMF variations). ETGs do not hide AM in their outskirts but loose it during their evolution and/or retain it in the hot gas component and the satellite galaxies that have not yet merged with the central galaxy.


Oktober 10: Dense gas and star formation in nearby galaxies  --  Lukas Neumann


November 3:  All Hands Meeting


Oktober 2023

Oktober 27:  Image reconstruction with GR - Results, Development and Prospects --  Felix Mang

One of the main science cases of GRAVITY is the investigation of the strong gravitational potential of SgrA*. Stellar orbits give information on the black hole's mass and distance and moreover can constrain its angular momentum via the Lense-Thirring precession. This effect however drops steeply with distance from the massive object and has not yet been detected in the motions of currently known stars. For the presently accessible magnitudes no star has been found with an orbit tight enough to reliably constrain the black holes spin. Hence, it is important to search for faint, yet unknown stars in the Galactic Center for which image reconstruction is an indispensable resource. For this science case, the image reconstruction tool GRAVITY-RESOLVE (GR) was authored in this group by Dr. Julia Stadler (now MPA) in 2022, which is specifically designed for Galactic Center observations with GRAVITY.

In my talk I will present a comprehensive overview of reconstructions of GRAVITY GC data from 2023 with GR, which give a strong indication that there might be a faint, yet undiscovered star present in the Galactic Center. Moreover, I give an update on my progress to tackle on of one of the shortcomings of GR, which is an excessive runtime for averaged sized datasets. This includes the acceleration of the employed model itself as well as the proposal of a new model which exploits the sparsity of stars in the FOV. Finally, I point out some future prospects for GR regarding further runtime and convergence optimization, as well as the possibility to extend the reconstructed FOV by combining the new model with the Mosaicing approach investigated in my Master's Thesis.


Oktober 20: What can we learn about SgrA* using polarimetry? --  Felix Widmann

Over the last years the interest in polarimetry on SgrA* has significantly increased, with observations in several different wavelengths and many new models and simulations. I will use this talk to summarize the newest polarimetry results from GRAVITY as well as look at what we have learned from radio observations. I will talk about some of the modelling and simulation studies and discuss what we can expect in the future.


Oktober 6: Astrometric detection of planets around M-dwarfs with GRAVITY --  Guillaume Bourdarot

The detection and characterization of low-mass planets in our close solar neighbourhood is a major challenge of exoplanetary science. Here, I will give an update of our long-term GTO program of the binary M-dwarf GJ65AB, located at d=2.67pc from the Sun, and potential evidence for a planet candidate in this system. The precise astrometry of the binary was measured through an astrometric monitoring from 2016 to 2023 using GRAVITY dual-field capability. We provide new measurements of the astrometric motion of the binary star and the estimation of the orbital parameters with extreme accuracy, with typical errors of 50-60µas per individual epochs with 1.5h observing time on the 1.8m Auxiliary Telescopes. The astrometry allows to analyze the residuals of the orbit in order to constrain the presence of planetary companions through their reflex motion on the binary host, which points to the presence of a Neptune-size companion formed within the stability region of the binary host. This study is the most extensive astrometric monitoring of a close stellar system, and potentially demonstrates the ability to reach a few tens of microarcsecond astrometric accuracy from the ground in narrow-angle astrometry in order to detect planetary system through their reflex motion.


September 2023

September 29: A new stacking technique to reveal the rotation curves of high-redshift galaxies. --  Jean Baptiste Jolly

In this tea talk I will introduce a new stacking technique that we are developing, which was designed to reveal the rotation curves of high-z galaxies, up to larger radii than otherwise possible. I will explain the main concept behind the method and discuss the functioning principle of the associated algorithm. Then talk about the main challenges and current solutions. Finally I will present some highlights of the overall performance of the method, when applied to mock galaxies.


September 22: 

Survey the distant dusty star-forming galaxies: go deeper and wider --  Jianhang Chen

Planet-forming disks substructures with ALMA at high angular resolution --  Nicolas Kurtovic


September 15: G1-2-3 --  Stefan Gillessen

Gas clouds in the central arcsecond of the Milky Way are remarkable. They show two more features in their orbital motions, not present for stellar orbits: 1) they evolve tidally and 2) they are measurably subject to non-gravitational forces. I will review the case of G2, with its dramatic tidal shearing, the detection of its deceleration and its connection to G1. And finally, fresh from the 2023 ERIS data, a source which truly should be called G3.


September 8: Star formation and molecular gas in ‘post-starburst galaxies' -- Dieter Lutz


July 2023

July 28: The MPE-UdeC Partner group: Second year report and CRISTAL --  Rodrigo Herrera-Camus

In this tea talk I will briefly summarize the activities of the Partner Group between MPE and UdeC during its second year, and I will present some of the first results from the CRISTAL ALMA Large Program (, which is the first systematic survey of the gas, dust and stars on kiloparsec scales of star-forming galaxies at z~4-6.


July 21: An update on the high-z quasar GRAVITY(+) program --  Taro Shimizu

I will give an update on the high-z quasar program we have started with Gravity-Wide and will continue with full Gravity+. This will include an overview of our current Nature paper, some new observations and early results, and development of a new quasar catalog from which to select targets.


July 14: In what ways are language models like ChatGPT useful for us? --  Juan Espejo

In recent months, the widespread acclaim for large language models (LLMs) like ChatGPT has ignited a remarkable surge of interest spanning various industries, underscoring their remarkable potential. While maintaining a healthy dose of skepticism is crucial, it is pertinent to recognize that these tools already offer practical value and could potentially be integrated into some of our daily work routines. Rather than dismissing them outright, it is advantageous to cultivate a discerning judgment to identify when and how these tools can be effectively employed, as well as when to avoid them. This presentation serves as an introductory guide to language models, focusing on their practical applications and inherent limitations within the specific context of our work. To do this, I will show some practical examples and discuss some of the upcoming developments that will naturally become commonly used in the near future.


July 7: Orbital precession of S-stars in the Galactic center --  Matteo Bordoni

The development of GRAVITY allowed to test, for the first time, the relativistic effects in the orbit of S2, or better the corrections to the Newtonian model given by the first-order terms of the post-Newtonian (PN) approximation of General Relativity (GR). In particular, after the star reached the pericenter of its orbit in 2018, we have been able to observe the in-plane, prograde precession of its orbit, that is compatible with what expected by a first-order PN approximation of GR.
Here I will discuss what level of quality can be reached in the determination of the orbital precession when using the post-Newtonian scheme, which is approximated but allows the inclusion of various effects, like that of a possible spin of the SMBH. I will discuss which is the role of the spin on the orbital precession, and how the detection of deeper S-stars could in principle allow us to measure Sgr A* spin.


June 2023

June 23: Updates on GRAVITY interferometric observations of the innermost hot dust structure around AGN --  Yixian Cao

The properties of the hot dust component around AGN traced by the near-IR continuum provides critical insights to some of the fundamental questions regarding the innermost AGN dust structure and its connections to the central engine. In this talk, I will present our latest measurements of the hot dust structure sizes of 17 type 1 AGNs from VLTI/GRAVITY interferometric observations. We find a size-luminosity relation with a slope of 0.4, flatter than the expected slope of 0.5 if the dust sublimation sets the inner boundary of the dust structure. In addition, there is a systematic offset between the size-luminosity relations from interferometric measurements and from continuum reverberation mapping. We also find a strong correlation between the host dust structure size and the broad line region (BLR) size. I will discuss the possible mechanisms for the shallower slope of the size-luminosity relation, the constraints on dust geometry and composition by comparing observations with clumpy dust models, and the inferred black hole masses using the host dust size based on its correlation with the BLR size. I will finish by highlighting the prospects of studying the dust structure based on future GRAVITY(+) observations.


June 16: The Galaxy Evolution Subgroup Science Topics --  Capucine Barfety

The aim of this tea talk is to summarise the science focus and goals of the GALEV subgroup in the IR group, as observations are now on-going for the two new surveys led by the team, GALPHYS and NOEMA3D. The talk will cover a broad overview of the subject, before diving into the past work accomplished by the team, as well as the questions and results that were looked at concerning the evolution of star forming galaxies at and since cosmic noon. Finally, I will connect that with the work currently being done in the group, now and in the near futur, and how it came to be, from studying the population trends to looking at smaller scale processes.


May 2023

May 5: An Update on GRAVITY+ --  Frank Eisenhauer


April 2023

April 28: Mrk 509, PDS 456, and a new R-L relation with GRAVITY --  Daryl Santos

This talk will be a continuation of my previous tea talk about constraining the broad-line region (BLR) size and supermassive black hole (SMBH) mass of Mrk 1239 and IC 4329A with GRAVITY. I will discuss two more objects, namely Mrk 509 and PDS 456, which were observed together with Mrk 1239 and IC 4329A through our Large Program focusing on observing type 1 active galactic nuclei (AGNs) with GRAVITY. With GRAVITY, we can resolve the BLR via spectro-astrometry, a technique where photocenter offsets of individual velocity channels are observed, providing BLR size measurements of high precision (about an order of 10 µas) and BH mass estimates via dynamical model fitting. We have successfully resolved the BLR of these two objects and measured their BLR sizes and SMBH masses. We find that their BLRs are best fitted with a thick BLR disk dominated by outflowing clouds. Midplane obscuration and preference of broad line emission to originate from the near side of the BLR cause the asymmetric differential phase signals of Mrk 509 and PDS 456, respectively. A model-independent reconstruction of the photocentres of their line profiles’ spectral channels reveals an offset between the BLR and dust continuum photocentres. These offsets were also measured for previously observed and published AGNs with GRAVITY, and are shown to have a tight positive correlation with AGN luminosity. We explain this as a result of asymmetric K-band emission from the hot dust, which can be simply modelled as a ring of dust composed of a fainter side and a brighter side. Lastly, we derive a new R-L relation using only GRAVITY-observed AGNs. We find a slope of α = 0.402 ± 0.157 and an intercept of K = 1.560 ± 6.996, which is consistent with the R-L relation of Bentz et al. (2013) within uncertainties, with possible flattening at higher luminosities.


April 21: Disagreeing with your Collaborators: inflow vs outflow in NGC7172 --  Richard Davies

April 14: Disk kinematics at high-z: comparing fitting techniques and modelling tools --  Lillian Lee

With the increasing data quality of IFU data, various fitting approaches have also emerged, each developed and tested by the creators. However, there has yet to be a systematic comparison of the multiple tools using a controlled set of simulated galaxies where the truth is known. Given the existing tension between results by different groups, it is eminent to fully characterise the different techniques. To address this, I investigated two parametric tools (DysmalPy and GalPak3D) and a titled-ring modelling tool (3DBarolo) to assess their intrinsic kinematics recovery. My experiment employs mock analytical models and considers different resolutions, signal-to-noise ratios (S/N), and galaxy properties that follow established scaling relations at z > 0.5. Results indicate that the three tools recover rotation velocity well, but there are differences in code-specific templates for the recovered velocity dispersion. The tilted-ring approach is particularly sensitive to S/N. These findings highlight the importance of high S/N out to larger radii and high spectral resolving power to constrain the intrinsic dispersion profile of high-z galaxies. Only then can we leverage the capability of non-parametric modelling and establish an appropriate prior function for parametric modelling to accurately characterise the dynamical evolution over redshifts.


March 2023

March 31: A selective review of supermassive black hole binaries and GRAVITY observations --  Jinyi Shangguan

Supermassive black hole (SMBH) binaries can be formed in massive galaxy mergers. The evolution of SMBH binaries is important for SMBH evolution and gravitational wave observations. In this tea talk, I will review the status of observational and theoretical studies of SMBH binaries. After decades of efforts, dual AGNs with separations of kpc scales have been discovered by various techniques out to redshift 2. Hundreds of candidates of sub-pc SMBH binaries are proposed, although the robustness of the selection methods remains questionable. In the transitional stage, 1-100 pc binaries are rare in part due to the lack of techniques to discover such systems. From the theoretical point of view, it is still challenging to conduct population studies of SMBH binary evolution using cosmological simulations. On the other hand, recent high-resolution isolated merger simulations found that the circumbinary disk can exert both positive and negative torques on the binary. Therefore, the binary may stall at parsec scales up to Gyr time scales. I will end the talk by summarizing the possible methods to detect SMBH binaries from ~100 pc to sub-pc separation with VLTI/GRAVITY.

March 3: Is it a Black hole?-- Diogo Ribeiro

Monitoring the few central parsecs of our galaxy over the last few decades has given us precise insight into the nature of the mysterious compact massive object SgrA*. Remarkably, the observed behavior of matter and light around this object matches to astonishing accuracy that of the predicted one by the Theory of General Relativity - We seem to have a Black hole at the heart of our galaxy. However, the ever more precise observations allow us to test this hypothesis to unmatched precision. In tomorrow's tea talk, I'll review some of my recent work toward this goal.


February 2023

February 10: CO and CI mapping in nearby galaxies, their traced ISM properties, stellar feedback and conversion factors, and clues to high redshift galaxies -- Daizhong Liu

I would like to present my latest works about high-J CO and CI mapping in nearby galaxies and shed some light on the CO dissociation and CI enrichment by stellar feedback in starburst environment, and link these local results to our high-redshift studies. This local galaxy work is based on the ALMA CO(4-3) and [CI](3P1-3P0) mapping, archival lower-J CO mapping, and new PHANGS-JWST near-/mid-infrared imaging within the PHANGS collaboration. My radiative transfer modeling including the effect of varying gas temperature, density and CI/CO abundance ratio reveals that there are trends in the temperature, density and CI abundance along with the bar-driven gas flow motions within a nearby galaxy center (r < 1 kpc). These trends agree with the scenario of strong stellar feedback heating up the gas and dissociating the CO into CI on the way. The high CO dissociation in starburst environments also makes the ideally constant CI-to-H2 conversion factor varying with the CI abundances. I further show a preliminary work on understanding the conversion factor of CO and [CI] lines in an analytical way. The analysis shows that these conversion factors strongly depend on a good knowledge of the gas temperature and density conditions and the CO or CI abundances.


February 3: Beam Compressor Differential Delay Line -- Jonas Sauter and Patrick Wessely

GRAVITY Wide comprises an upgrade of the existing beam compressors to incorporate the current PRIMA Differential Delay Line (DDL) functionality. This will save five optical reflections in the science-target beam and consequently increase the optical throughput. We build up a BCDDL mock-up system comprising the metrology beam path, the underlying hardware, and the controlling real-time system. We were able to derive a functional system that can correct differential optical path differences in the order of 10 nm.
In the talk we will present the status of the BCDDL mock-up and give a short introduction to its hardware design and control architecture.


December 2022

December 16: Probing the inner planet-forming zones of disks with mid-infrared spectroscopy -- Giulio Bettoni

Protoplanetary disks are the rotating structures of dust and gas in which planets are formed. In the past decade, ALMA has allowed studying the cold dust and gas of the outer part of disks. The inner region within 10 AU plays a crucial role in the evolution of the entire disk and planet formation but can only be marginally probed by ALMA. In contrast, infrared spectroscopy is a powerful tool to study the warm gas emitting from the inner disk. Thanks to new state-of-the-art facilities such as the VLT-CRIRES+ and JWST-MIRI instruments, it is now possible to significantly improve our understanding of the inner regions of disks.

In this talk, I will discuss how ground-based high-resolution and space-based medium-resolution spectrometers can probe the physical and chemical structure of the inner disk. I will present my work on the CRIRES+ Science Verification observations of the SCrA binary system as an example of how the kinematics and the physical structure of the inner disk can be studied.  I will also present the first JWST mid-infrared detection of abundant carbonaceous molecules in the disk of a very low-mass star, highlighting how JWST-MIRI will help constrain the chemical composition of the inner disk and the processes that are occurring in the terrestrial planet-forming zones.


December 2: First on-sky results of ERIS at VLT -- Kateryna Kravchenko

ERIS is a new adaptive optics instrument installed at the Cassegrain focus of the VLT-UT4 telescope at the Paranal Observatory. ERIS consists of two near-infrared instruments: SPIFFIER, an integral field spectrograph covering J to K bands, and NIX, an imager covering J to M bands. ERIS has an adaptive optics system able to work with both LGS and NGS. The AIV phase of ERIS at Paranal was completed in winter 2021-2022, followed by several commissioning runs in 2022. In this talk I will present the first results of the on-sky performance of ERIS during its commissioning and preliminary scientific results.


November 2022

November 25: The science of scientific writing -- Stefan Gillessen


November 18: An update on SgrA* Flares in Astrometrie & Polarization  -- Felix Widmann


November 4: The Universe and I - musings about the usefulness of astronomy -- Eckhard Sturm

As part of my work I often have to justify the value of astronomy for humankind. Often in an economic context or in terms of technology return. Be it in reports to funding agencies (e.g. DLR), talking to politicians (and other decision makers), or in public talks in schools, in the Volkshochschule (adult education centers), or at parties. I have collected (more or less) usefull arguments that I want to share and discuss with you.


October 2022


October 14: Overview of Galactic Center observations with GRAVITY in 2022 -- Antonia Drescher

In this tea talk I will give an overview of Galactic Center observations with GRAVITY that we had this year. I will start with explaining the motivation for the observations and present the questions that we’re trying to answer. With the main goals for this year of catching a flare, which is hot gas that orbits Sgr A*’s event horizon, tracing the orbits of stars with pericenters that just happened or are soon to come, and deep imaging to search for unknown faint stars, we monitored Sgr A* over a period of 7 months, from March to September 2022. I will show results obtained from imaging with CLEAN, discuss which of the above mentioned goals we could achieve, which difficulties we faced this year, and where we stand with the analysis of the data.

October 7: Verification of MICADO Cold Optics -- Federico Biondi

Even if the MICADO team is facing the fourth Final Design Review, the project has already entered the MAIT phase. Consortium partners are getting ready for the integration of the sub-systems and are finalizing and procuring the equipment for the test setups. The complexity of the instrument and the strict requirements demand for a solid test campaign for components and sub-systems. Besides being the PI institute for MICADO, MPE is also responsible for its cryostat and de-rotator, for the focal plane and detector positioning mechanisms, and for the Cold Optics. In this talk I will describe the tests foreseen for the Cold Optics, giving some details on the relation between the requirements to validate and the planning and construction of the proper setup and equipment.


September 2022

Septemper 23: "Hitting Two Objects with One Instrument": Constraining the BLR size and SMBH mass of Mrk1239 and IC4329A with GRAVITY -- Daryl Santos

GRAVITY, the second-generation Very Large Telescope Interferometer (VLTI) instrument, recently paved the way for BH mass measurements by resolving the broad-line region (BLR) via spectro-astrometry, a technique where photocenter offsets of individual velocity channels are observed, providing BLR size measurements of high precision (about an order of 10 µas) and BH mass estimates. In this talk, I will discuss the current progress of our analyses of GRAVITY interferometric spectra of Mrk1239 and IC4329A, two of type 1 active galactic nuclei (AGNs) observed through our Large Program. We reveal the BLR of these objects to be ~135 μas (0.055 pc) and ~40 μas (0.013 pc) offset from their continuum photocenter via model-independent reconstruction of photocenters of the spectral channels of the Brγ, respectively. However, only the photocenters of IC4329A showed a significant (~5.3σ) clear velocity gradient that is almost perpendicular to its offset. We marginally resolved the BLR of Mrk1239 (IC4329A), thus providing a 3σ upper limit of log ΘBLR (ld)= 2.12 (1.55) for the BLR radius which is consistent with the BLR radius-luminosity relation of nearby AGNs derived from reverberation mapping campaigns. Our dynamical modeling also indicates 3σ upper limits of log MBH/M = 8.23 (8.36) for the BH mass, which are also consistent with the standard MBH-σ* relation for early-type galaxies.


Septemper 9: Introduction of new group members


The specific angular momentum of ETGs --  Claudia Pulsoni

    Mass and angular momentum (AM) are key parameters to understand galaxies. Their co-evolution establishes a tight relation between the stellar specific AM (j*) and the total stellar mass (M*) for disk galaxies. The case of massive early type galaxies (ETGs) is far less explored, as a large fraction of their AM is distributed at large radii where stellar spectroscopy is unfeasible. 

    In this talk, I present results for 32 nearby ETGs based on 2D kinematics out to a mean 6 effective radii with planetary nebulae (PNe) as kinematic tracers of the stellar halos and integral field spectroscopy in the central regions. We estimate projection effects and correct for the limited radial coverage of the PN data using simulated ETGs from IllustrisTNG. The results show that, once j* is integrated out to large radii, ETGs have systematically lower j* than spiral galaxies with similar M*. Their j* is not “hidden” in the outskirts but must be lost during their evolution or distributed among the hot gas component and the satellite galaxies that have not yet merged with the central. 


In-Situ Formation of the Intra-Cluster Light at High Redshift  --  Capucine Barfety

    The Intra-Cluster Light (ICL) traces one of the key components of galaxy clusters. Centred around the core of the cluster, this diffuse halo of light made up of unbound stars is by its very nature a challenge to identify and study. As of today, studies find that the ICL assemble mostly below z=1, through tidal interactions between cluster members, with little evidence of significant ICL above z=1. In this project, I focused on measuring the amount of stellar mass unbound to any galaxy sitting in the core of a disrupted starbursting cluster at z=1.71; using near-infrared high-resolution imaging from the Hubble Space Telescope. I estimate that between (2.2 ± 0.5) × 10^10 M⊙ and (6.6 ± 1.2) × 10^10 M⊙ - depending on the data processing method - of stellar mass has already formed in the area. In addition, these stars are co-spatial with a large molecular gas reservoir (~1 × 10^11 M⊙), a large star formation rate (~860 M⊙/year), and X-ray emissions consistent with the presence of a cooling flow. All these elements combined together point towards in-situ formation of a substantial portion (10-21%) of the ICL in this cluster.


How did I get here?  --  Diogo Ribeiro

    Coming from the westernmost capital in Europe Diogo is one of the new PhD students recently arrived to the IR-GC. Back in Lisbon, Diogo worked at the GRIT group with Professor Vítor Cardoso and Miguel Zilhão on how ultralight bosonic dark matter can shape the evolution of binary systems of black holes.

    Moving to Garching, his work will focus on how the ever more precise data from the galactic center can be used to test GR to new limits. In this short talk he will tell you a bit about himself, his previous work, and his expectations for the years to come.


From Rome to Garching: my scientific interests  --  Matteo Bordoni

    I am a new PhD student in the Galactic Center (GC) group coming from Rome, Italy. I graduated in Astrophysics at "La Sapienza" University in Rome and worked with Prof. Roberto Capuzzo Dolcetta on theoretical aspects related to the orbital precession of S-stars in the GC and on the possibility of measuring the spin of Sgr A* through the detection of deeper S-stars. I am really excited to be here in Garching, having the unique possibility of working with the GRAVITY data and with the top scientists in the field.


July 2022

July 22: Shapes, transformations, and a pinch of gentle feedback -- Junkai Zhang and Stijn Wuyts (University of Bath)

3D shapes of galaxies encode crucial information on their formation process.  In this duo presentation, we start out by characterizing the intrinsic shapes of quiescent galaxies, across a range in mass, redshift, environment and surface brightness profiles.  A comparison to TNG simulated galaxies points at enhanced ex-situ stellar mass fractions as a source of their 3D shape transformation, but also reveals a shortcoming of cosmological simulations, namely in producing thin stellar structures.  We then turn to observations of star-forming galaxies, where the combination of projected axial ratios, galaxy sizes and SED shapes informs us on their dust attenuation, dust content and star/dust geometry.  We address the puzzle to reconcile inferences on dust properties from far-infrared observations on the one hand, and from attenuation estimates and their inclination dependence on the other hand.  Using TNG50, we ask ourselves the question what galaxy obervables -within the context of the simulation- are predictive of future bulge growth.  Finally, time permitting, we will summarize lessons learned from analyzing ionized and neutral gas winds observed among a large sample of normal nearby galaxies, selected from the MaNGA imaging spectroscopic survey.


July 15: Two stacking analyses of lensed galaxies -- Jean-Baptiste Jolly

In this tea talk I will present two stacking analyses of lensed galaxies behind galaxy clusters, from the ALMA Lensing Cluster Survey (ALCS). In the first (Jolly et al. 2021) we studied the [CII] emission line from 52 faint galaxies at z~6. More specifically we looked into the relationship between the stacked [CII] line luminosity and the average SFR of our sample, and compared it to local relationship. In the second analysis --still underway-- we performed continuum stacking of all the galaxies at z>1 in the 33 galaxy clusters observed in the ALCS. From these we derived dust mass evolution as well as comoving dust mass density evolution, from z=1 to z>5. I will finally briefly introduce the novel "symmetric-stacking" method and discuss its potential impact on future stacking analyses.


June 2022

June 3: MeerKAT, rotation measure and the cosmic magnetism -- Feng Gao

In this tea talk I will first give a brief introduction on MeerKAT, its observing capability and latest updates. Then I will switch the focus onto the science topic I’m interested, namely the cosmic magnetism, explaining why we care about magnetic field and why radio interferometer is the best tool to measure it. Finally I will report on the latest development of a new rotation measure synthesis algorithm I’m working on and how we can push the limit for solid rotation measure to fainter targets. 


May 2022

May 13: The Accretion Rate-Disk Mass Relationship in Intermediate-Mass Stars -- Sierra Grant

The accretion rate-disk mass relationship connects the evolution of protoplanetary disks at the star-disk connection to the outer disk mass reservoir. This relationship has long been predicted and has been seen observationally in recent years, teaching us how disks evolve with time. However, most observational efforts have been biased towards low-mass stars. On the other hand, more massive stars have lacked the extensive (sub-)millimeter observations needed to determine the disk masses. In this talk I will present the accretion rate-disk mass relationship for a sample of intermediate-mass stars, highlighting how these objects differ from their low-mass counterparts and what may be driving those differences. I will also discuss a bias in the intermediate-mass sample and how that limits our understanding of late-stage disk evolution around these objects. 


April 2022

April 29: An Observational Overview of Protoplanetary Disks -- Sierra Grant and Guillaume Bourdarot

In this special tea talk, we will give an introduction on our current knowledge of protoplanetary disks by presenting the observations at multiple scales (from a few stellar radii to hundreds of AU) and multiple wavelengths (near-IR, mid-IR, and submillimeter wavelengths). We highlight the complementarity between techniques probing the same scales at different wavelength (e.g., CRIRES+, GRAVITY, ALMA/NOEMA). In particular, we emphasize the unique capability of CRIRES+ and GRAVITY to probe the inner 10 AU of protoplanetary disks. Throughout the talk use on disk, HD 100546, as an example for which an extensive dataset is available to use for a multi-wavelength analysis.


April 8: Imaging with G^R -- Felix Mang

In this talk I will mainly focus on the imaging results of the first observing campaign in 2022. Additionally, I will introduce you further into the code of G^R and give you an update on my current work.

I analyzed various pointings by imaging them and by determining the positions of their corresponding sources. Besides minor deviations from the expected star positions in the SgrA* pointing, S300 in the West pointing showed a considerable offset to predictions. Moreover I will lay out my strategy to obtain unbiased position estimates of known stars in addition to deep images.


April 1: The first year of the MPE-UdeC Partner group -- Rodrigo Herrera-Camus

I will present a summary of the work done by our Partner Group during its first year of existence. First I will highlight the results from the Master thesis of two recently graduated students that used NOEMA observations to study the ISM properties of a massive, star-forming galaxy at z=2 (MD94), and one star-forming galaxy at z=7.2 (GN108036). Finally, I will present the main results of our kinematic analysis of the main-sequence galaxy HZ4 at z=5.5 (Herrera-Camus et al. 2022), and I will introduce the ALMA Large Program CRISTAL for which we are starting to get the first data products.


March 2022

March 25: JWST: new adventures in galaxy and AGN evolution -- Daizhong Liu and Jinyi Shangguan

The James Webb Space Telescope (JWST) has just made breathtaking (calibration) observations and will soon be conducting science observations in the mid of this year. It's more than twice better angular resolution than HST, orders of magnitude better sensitivity than Spitzer, unprecedented coverage of ~1–28μm, and large amount of early-release-science and treasury surveys will greatly benefit the high-z community and significantly push the high-z galaxy and AGN evolution fields forward. In this Special Tea Talk, we will briefly and selectively summarize the expected key scientific breakthroughs of JWST cycle 1 high-z galaxy and AGN evolution programs, and illustrate how we can prepare for and benefit from the upcoming surveys for our group. 


March 4: The Data Reduction Pipeline for the MICADO Instrument -- Yixian Cao

As an integral part of the MICADO project, the MICADO data reduction pipeline is designed to provide data products ready for scientific analysis and instrument health monitoring from the raw data produced by the instrument. The pipeline supports all the four observation modes offered by MICADO: standard imaging, astrometric imaging, high contrast imaging, and slit spectroscopy. The pipeline software will be implemented in the ESO software framework, using the Common Pipeline Library and the High-level Data Reduction Library developed by ESO. For a successful implementation, the pipeline should timely and robustly produce processed data that meets quality requirements of each observation mode. To achieve this goal, simulated data and instrument test data will be used for the pipeline testing. I will summarize the scope and overall design of the pipeline software, present key algorithms for astrometric calibration, and give an overview about the current status of the development.


February 2022

February 25: Massive high-z disk kinematics under the microscope of strong lensing: Low dark matter fraction and inside-out quenching in the massive galactic disk of J0901 at z=2.259 -- Daizhong Liu

It is well-known that massive galaxies have the mass-quenching mechanism leading to the color bimodality seen in the present Universe. However, how the mass-quenching happens in massive star-forming galaxies (SFGs) at high-z are still not well understood. Here we study a unique case of a strongly-lensed z=2.259 SFG, J0901, which happens to be one of the most massive (log(M*/M☉)≥11.0) SFGs at Cosmic Noon (z~1–3) and harboring a mild AGN-driven outflow. Our new CO(3–2) imaging with ALMA probes an extended, ring-like cold molecular gas distribution and its kinematics out to ~5 kpc (~1.5 times the disk effective radius R_e), at a best delensed resolution of ~600 pc. Together with an even better resolved inner rotation curve, and a lower resolution outer profile from the AO-assisted and seeing-limited SINFONI/VLT data, respectively, we find that J0901 has a high baryon surface density and low dark matter mass fraction within R_e, strongly confirming the lower-resolution trends in ~100 unlensed massive SFGs. Our high-resolution data further reveals a large gas instability (Toomre’s Q ≪ 1) in its molecular gas ring, implying a rapid completion timescale of the ongoing inside-out quenching within about five orbital times. Finally, I will present an outlook for key future observations and coding development, e.g., with ALMA, ERIS and JWST, and multi-tracer fitting, which are crucially needed to reduce the uncertainties and constrain the rotation curve and dark matter beyond 1.5 R_e in this unique exemplar of massive SFGs with inside-out quenching caught in the act. 


February 18: Different methods to resolve AGN broad line region -- Jinyi Shangguan

To resolve the broad line region (BLR) of active galactic nuclei (AGNs) is almost the only method to measure the supermassive black hole mass in the distant Universe. In this tea talk, I will summarize four different methods that are able to constrain the geometry and kinematics of the BLR. The reverberation mapping and GRAVITY interferometry techniques have been extensively discussed in our group. I would like to summarize the main physical challenges that we currently encounter. They motivates us to look for other techniques to constrain the BLR structure. I will introduce what can be learned from spectropolarimetry and microlensing of lensed quasar. Some ideas of synergies of GRAVITY(+) observations with these methods will be discussed.


February 11: Globular Cluster Formation as a case of Overcooling -- Alvio Renzini

Observations, especially HST photometry and VLT spectroscopy, have revealed an extreme complexity of the stellar content of globular clusters, with multiple populations being characterized by different chemical compositions resulting from different degrees of CNO cycling, proton-capture processing and helium enrichment. Thus, all globular clusters formed, not in a single, but in a series of star formation episodes, with different complexity from one cluster to another. How this did happen, what kind of stars produced the nuclearly-processed material and which kind of environment gave birth to globular clusters are all highly debated issues with no consensus having emerged so far.
In a recent paper (Renzini, Marino & Milone, submitted), driven by observational findings, we select massive interactive binaries as the most suitable among the existing candidates for producing the chemical patterns typical of multiple populations. To avoid supernova contamination we are further driven to endorse the notion that above a critical mass stars fail to produce supernova events, but rather sink into black holes without ejecting much energy and heavy metals. This assumption has the attractive implication of suppressing star formation feedback for some 5–10 million years, leading to runaway star formation, analogous to overcooling that in absence of feedback would have turned most baryons into stars in the early Universe. Under such conditions, multiple episodes of stars formation, incorporating binary star ejecta from previous episodes, appear to be unavoidable, thus accounting for the ubiquity of the multiple population phenomenon in globular clusters. If this is the way globular clusters formed, such delayed supernova feedback may play a role in other star formation circumstances, such as the formation of nuclear star clusters and giant clumps in high redshift galaxies.


February 4: Introduction of new group members

Probing the terrestrial-planet forming zone using multiple tracers -- Sierra Grant

The study of protoplanetary disks benefits from a multi-wavelength and multi-method approach. This allows for the study of the gas and the dust over a range of spatial scales and temperatures. After my previous work using far-infrared and millimeter observations to trace the outer regions of disks, my recent focus has turned to near- and mid-infrared observations. I will briefly introduce three ongoing projects: 1) the characterization of the accretion rate—disk mass relationship for intermediate-mass stars, 2) using both high spectral and spatial resolution data to uncover the structure of the inner disk, and 3) the reduction and analysis of new CRIRES+ L- and M-band observations. Overall, these projects all probe the gas within a few AU of the central star and will give us a better understanding of the disk gas and dust structure. From this, we can investigate the evolution of these systems and the physical conditions in the terrestrial planet-forming zone.

The impact of external photoevaporation on the evolution of protoplanetary disks in the σ - Orioins Cluster -- Giulio Bettoni

Protoplanetary disks are the structures surrounding young protostars, in which planets are formed. Today there is strong evidence that viscosity is the main actor in the evolution of disks. However, other processes can occur, such as external photoevaporation, which is the external dispersion of a disk, due to the impact of Ultraviolet radiation fields emitted by the nearby class O-B stars. Models predict that this process would decrease the ratio between the disk mass M_disk and the mass accretion rate M_acc at which the disk gas accrete onto the central protostar.
In this tea talk I will present the results of my Master thesis that I did at the University of Milan. The aim was to quantify the impact of external photoevaporation on the evolution of protoplanetary disks. To reach this goal, we studied the spectra measured by the X-Shooter instrument of Very Large Telescope, of 31 targets in the σ - Orionis Cluster. By applying a fit procedure developed by Manara et al (2013), we derived M_acc for each target. We then studied the relation between the M_acc and the disk mass M_disk for the 31 targets, and for 8 additional targets taken from literature, looking for the expected signatures of external photoevaporation. We also searched for another signature of external photoevaporation, i.e. the profile and ratio of some forbidden lines from [NII] at 654.8 and 658.3 nm and [SII] at 671.6 and 673.1 nm. We took this information both from the study of our X-Shooter spectra and from previous studies.
We found that external photoevaporation is affecting the disks population within a projected distance from the σ -Ori stellar system of 1.2 pc, and possibly out to 2 pc.

Guillaume Bourdarot

In this introductory tea talk, I will present the work I developed during the three years of my PhD in Grenoble at IPAG. This work focuses on the study of young stars and their protoplanetary disks at the astronomical unit scale with infrared interferometry. It includes both observational and instrumental aspects. In the observational part, I focused on the study of the accretion outbursts occuring in the formation of young stars, through the observation of the star FU Orionis with near infrared interferometry. In the instrumental part of this work, I explored the extension of infrared interferometers to the recombination of a large number of telescopes and kilometric baselines, to overcome the current image reconstruction capabilities of infrared interferometry. In this perspective, we revisited the architecture of heterodyne interferometry, pioneered by Pr C.H.Townes and his team at UC Berkely, at the light of the recent progresses in the field of mid-infrared technologies. We provided a sensitivity analysis of a new architecture, knowing the strong sensitivity limitations of heterodyne interferomery in the infrared. In order to address the problem of correlation bandwidth of a large number of telescopes, we introduced so-called photonic correlation schemes, and implemented a preliminary laboratory demonstrator at 10µm to validate the complete detection and correlation chain. Finally, based on the intrinsic scalability of this technique, we described how these ideas could be apply to a technological pathfinder combining the 8 telescopes of the Very Large Telescopes Interferometer (VLTI) at 10 μm.


January 2022

January 28: No Tea Meeting


January 21: Introduction of new group members (Yixian Cao, Daryl Santos, and Felix Man)


January 14:  Dependence of the CO-to-H2 conversion factor (X_CO) on metallicity, intensity, and spatial scale in the interstellar medium -- Chia-Yu Hu

Star formation occurs in molecular hydrogen (H2) gas. As H2 does not emit radiation under typical conditions, we need a tracer for H2, and carbon monoxide (CO) is the most widely used tracer. Observationally, the H2 mass is inferred from the CO emission via the so-called CO-to-H2 conversion factor (X_CO). However, X_CO is not a universal constant, and its dependence on physical parameters such as metallicity is still not well understood. In this tea talk, I will present our recent hydrodynamical simulations of a feedback-regulated multiphase interstellar medium. By constructing synthetic CO emission maps with radiative transfer calculations, we study X_CO across a wide range of metallicity (0.1 <= Z/Z_sol <= 3). We find that the kpc-scale X_CO can be overestimated at low Z if assuming steady-state chemistry or assuming that the star-forming gas is H2-dominated. On parsec scales, X_CO varies by orders of magnitude from place to place, and it drops to the Milky Way value of 2e20 cm^-2 (K km s^-1)^-1 once dust shielding becomes effective, independent of Z. Our predicted X_CO is a multivariate function of metallicity, line intensity, and beam size, which can be used to more accurately infer the H2 mass.


March 2020

February 2020

February 14: No Tea Meeting

February 7: No Tea Meeting

January 2020

January 31: Star-forming Galaxies at Cosmic Noon -- Natascha Foerster Schreiber

I will summarize selected aspects of our current knowledge from both censuses of population properties and detailed physical views of individual star-forming galaxies at z~1-3, and will highlight exciting prospects with upcoming instruments and facilities.

January 24: Metallicity measurements on galaxies -- Minju Lee

January 17: What sets the C/O ratio in giant exo-planetary atmospheres? -- Ewine van Dishoek

December 2019

December 6: The Molecular Gas Content of Local X-ray Selected AGN -- Taro Shimizu

For the past several years, BAT AGN Spectroscopic Survey (BASS) collaboration has been collecting CO spectra of local (z < 0.05) hard X-ray selected AGN, including my own IRAM 30m Large Program. I will present the initial results of the survey which represents the largest sample of molecular gas measurements of AGN host galaxies in the local universe. I compare the total molecular gas mass, gas fraction, and depletion time to a similar survey of inactive galaxies (xCOLDGASS) to assess the nature of galaxies hosting AGN as well as any potential impact the AGN could have on its host. Matching in both stellar mass and SFR, I find that AGN host galaxies have lower gas masses and gas fractions which then leads to shorter depletion times. 

November 2019

November 29: Hydrodynamical Simulations of the Interstellar Medium (ISM) -- Chia-Yu Hu

I'll give an (biased) overview of cosmological simulations of galaxy formation and discuss their current limitations, which motivate the need of small-scale ISM-resolving simulations. I'll then show some results of supernova-driven galactic outflows as well as dust and molecule (H2 & CO) formation that I plan to do at MPE.

November 22: No Talk -- IR Retreat

November 15:  Exoplanets -- Thomas Ott

I will give a brief introduction in the field of exoplanet research covering the current state of detecting and characterizing exoplanets, and an outlook for the immediate to the more long term activities. This is mostly based on the "Exoplanet Science Strategy" document of the National Academy of Science, written by Dave Charbonneau and Scott Gaudi (2018).

November 8: Polarization Measurements with GRAVITY -- Felix Widmann

I will give a summary about polarimetric observations with GRAVITY. While GRAVITY has all the capabilities of a polarimeter, some challenges arise due to the VLTI and make an additional calibration necessary. I will show what goes into this calibration, why it is necessary, and illustrate everything on an example dataset from the galactic center.

November 1: No talk -- All Saints Day

October 2019

October 26: Fast Infrared Observations of BHBs with CIRCE -- Yigit Dallilar

I will present selected observations of BHBs with CIRCE, mainly focusing on V404 Cygni. During our observations of the source, we discovered fast flaring activity in the infrared, in some cases reaching timescales less than a second. While the spectral index in the optical is consistent during quasi-continuous flaring activty as shown in the following night, our observations demonstrate irregular flaring activity with wildly changing spectral energy distribution at short timescales. This feature suggests rapidly changing physical conditions and inhomogeneities in the jet base. I will discuss the origin of the flaring activity and its possible relation to ejection events seen in BHBs. If time permits, I will talk about our experiences with fast infrared polarimetry using CIRCE.

October 18: Informal Discussion on Applying for Jobs -- Linda Tacconi

October 11: No talk

October 4: No talk -- Day after holiday

September 2019

September 27: No talk -- IR BBQ

September 20: The near infrared flux distribution of Sagittarius A* -- Sebastiano von Fellenberg

I will present the flux distribution created from the GRAVITY light curves obtained in the 2017 and 2018. During these periods we have been able to see Sgr A* in more then 97% of the 5 minute exposures. Because we see the flux distribution turn over, we measure the NIR median flux and the variability. This allows to place model-free constraints on the NIR SED. Furthermore, comparing the observed flux distribution (histogram) to model probability density functions shows that a single log-normal or power-law distribution function may not be enough to describe the observed fluxes.

September 13: GC Flare Modeling: an Update -- Michi Bauböck

I’ll discuss the current state of our understanding of the astrometry of flares at the Galactic Center. In particular, I’ll show the fits obtained by combining the data from multiple flares to constrain the radius, inclination, and position angle of the origin of the IR flares. 

July 26 - September 6

Summer Break

July 2019

July 19: Re-aligning the stars: distortion correction in the frame(s) of Gemini GeMS-GSAOI -- Vincent Garrel

 Similar to the future MPE-led ELT instrument MICADO with the AO module MAORY, the Gemini GSAOI is an imager covering 85x85 square arsecond with a mosaic of NIR-sensitive 20mas pixel scale detectors. GSAOI is fed by GeMS, a MCAO system providing routinely quasi-diffraction limited images (FWHM<90mas PSF in K-band, 10-15%-level uniformity over the full field) since 2013. Due to its conception, configuration and current operational model, the image distortion over the mosaic display a complex and varying pattern. I review the current popular science cases covered by the instrument and the need for more accurate calibrations. I introduce recent progresses on the comprehension of the phenomena inducing distortion. Then, with the help of an astrometric calibration mask I installed in 2017 and the GAIA DR2 high-precision data, I look how to model a varying World Coordinate Systems solution to deliver easy-to-use data for astronomers.

July 12: Subjective Report on Lindau Nobel Laureate Meeting -- Hannah Übler

I will give a subjective report on last week's Nobel Laureate meeting in Lindau - photos, personal highlights, thoughts - which could potentially lead to some discussion.

July 5: LBT & ARGOS -- Sebastian Rabien

With being handed over to the observatory, ARGOS is now available for the LBT community for regular observing.
In this tea talk I will give a brief overview on the LBT and it's instrumentation suite and report on ARGOS, the LBT's LGS ground layer adaptive optics facility. Under regular observing conditions, ground layer adaptive optics can decrease the PSF size by a factor 2-3, tailored to the two custom slit MOS spectrographs LUCI1 and LUCI2, enhancing their spectral and spatial resolution. I will report on the ground layer adaptive optics performance, and highlight some results from the ARGOS commissioning.

June 2019

June 28: The future of exoplanet characterisation is optical interferometry -- Sylvestre Lacour

For those of you who did not listen to my talk last week, I will redo it in a slightly different fashion. The context is still GRAVITY+, and the amazing results that we obtained during the last year. I will update you on paper 2 (on the exoplanet Beta Pictoris b), and on the latest observations. But of this session will be to talk about the next scientific objectives that we could reach with an upgraded GRAVITY. It does include GRAVITY+ along the way. But hopefully, there will be a GRAVITY++.

June 21: No talk -- Day after Corpus Christi

June 14: No talk -- Fachbeirat Rehearsals

June 7: Zooming in on AGN-Driven Outflows at z~2 with SINFONI-AO -- Rebecca Davies

AGN-driven outflows are detected in the majority of high mass galaxies at z~2, and are likely to play an important role in quenching star formation. However, the mechanisms by which AGN accretion energy couples to the surrounding gas and the efficiency of this coupling are the subject of ongoing debate. In this talk I will discuss the insights gained from a detailed analysis of three AGN-driven outflows at z~2, based on SINFONI-AO data. These three systems form a unique sample, because they allow us to study the impact of AGN-driven outflows from circumnuclear to intergalactic scales, and at different phases in the evolution of both the galaxy and the outflow.

May 2019

May 31: No talk -- Day after Ascension

May 24: S2 - an update -- Stefan Gillesen

The detailed monitoring of S2's motion through pericenter in 2018 with GRAVITY and SINFONI has provided us with excellent data. Our data set as of end 2018 detects
the gravitational redshift term now at the 20 sigma level, and the uncertainty of the distance estimate is at 0.3%. I will describe this latest analysis and the results, before turning
to the immediate future: The relativstic prograde precession in the S2 orbit should be detectable by the end of 2019, but comes with new challanges: The separation between S2 and SgrA* has increased in 2019 to a level that we need to change our observing strategy - which means that we face a new set of systematic errors. 

May 17: Polarisation signatures of hotspots around Sgr A* -- Alejandra Jiménez Rosales

Polarisation offers a new window to study light at event horizon scales and therefore have an insight into strong gravity, magnetic field configurations and plasma physics. I’ll present a study of the polarised properties of a simulated hotspot orbiting a black hole and show how these allow for mapping of the magnetic field configuration near event horizon scales for the first time and an estimation of the magnetic field strength, which has implications on basic accretion physics, including black hole growth and jet launching. I’ll also show a comparison to the recent GRAVITY collaboration near-infrared flare results (2018).

May 10: No talk

May 3: Corona Australis: a young region with old disks -- Paolo Cazzoletti

In recent years, the disk populations in a number of young star-forming regions have been surveyed with the Atacama Large Millimeter/submillimeter Array (ALMA). Understanding the disk properties and their correlation with the properties of the central star is critical to understanding planet formation. In particular, a decrease of the average measured disk dust mass with the age of the region has been observed, consistent with grain growth and disk dissipation. We conducted high-sensitivity continuum ALMA observations of  43 Class II young stellar objects in CrA. The continuum fluxes are used to estimate the dust masses of the disks, and a survival analysis is performed to estimate the average dust mass. We also obtained new VLT/X-Shooter spectra for 12 of the objects in our sample for which spectral type (SpT) information was missing. Twenty-four disks were detected, and stringent limits have been put on the average dust mass of the  nondetections. Taking into account the upper limits, the average disk mass in CrA is 6+-3M_Earth. This value is significantly lower than that of disks in othe young (1-3 Myr) star forming regions (Lupus, Taurus, Chamaeleon I, and Ophiuchus) and appears to be consistent with the average disk mass of the 5-10 Myr-old Upper Sco. The position of the stars in our sample on the Herzsprung-Russel diagram however seems to confirm that CrA has an age similar to Lupus. Neither external photoevaporation nor a lower-than-usual stellar mass distribution can explain the low disk masses. On the other hand, a low-mass disk population could be explained if the disks were small, which could happen if the parent cloud had a low temperature or intrinsic angular momentum, or if the angular momentum of the cloud were removed by some physical mechanism such as magnetic braking. Our results suggest that in order to fully explain and understand the dust mass distribution of protoplanetary disks and their evolution, it may also be necessary to take into consideration the initial conditions of star- and disk-formation process. These conditions at the very beginning may potentially vary from region to region, and could play a crucial role in planet formation and evolution.

April 2019

April 26: The Star Formation Histories of Quiescent Galaxies -- Sirio Belli

The stellar light emitted by high-redshift galaxies contains absorption lines that can be used to derive the past histories of these systems, and estimate their ages. I will discuss the spectral fitting technique that makes this possible, and present recent results from the analysis of deep Keck spectra of quiescent galaxies at 1<z<2.5.

April 19: No talk - Good Friday

April 12: No talk

April 5:  Continuum and Line FItting for circumstellar disks -- Yao Liu

We present CLIcK, a flexible tool to simultaneously fit the continuum and line emission for circumstellar disks. The DDN01 continuum model (Dullemond et al. 2001) and a plane-parallel slab of gas in local thermodynamic equilibrium are adopted to simulate the continuum and line emission respectively, both of them are fast enough for homogeneous studies of large disk samples. We applied CLIcK to fit the observed water spectrum of the AA Tau disk and obtained water vapor properties that are consistent with literature results. We also demonstrate that CLIcK properly retrieves the input parameters used to simulate the water spectrum of a circumstellar disk. CLIck will be a versatile tool for the interpretation of future James Webb Space Telescope spectra.

March 2019

March 22:  A conference summary: is our changing look now only partially obscured? -- Ric Davies

These are the same slides I used at the AGN meeting held at the end of 2018. I will reflect on the talks and posters presented during that meeting, to assess the current status of our understanding of the 'torus'. I will address how our picture has developed in recent years. And I will emphasize how we need to think of the torus in the context of the structures around it on both larger and smaller scales; put some focus on temporal aspects; and consider some pitfalls.

March 15: Electron densities of two dusty starbursts at z=4.7 using [NII] lines at far-infrared -- Minju Lee

The most massive galaxies in the local universe are often located in clusters and the fossil record of their stellar population indicates the formation epoch of z~5 with bursts of star formation. However, the detailed physics of the formation mechanism and the impact from/to the environment during the formation are largely unconstrained. Dusty starbursts and quasars at high redshifts have been considered as promising progenitors of these massive populations, which could help to pin down the unknowns above. With this motivation, we have been studying a pair of dusty starbursts (SMG-QSO) at z=4.7 in detail. In this tea talk, I will present recent progress based on the detection of [NII] lines at 122 um and 205 um using ALMA. The detection allows us to constrain the electron densities of the two dusty starbursts for the first time at this redshift, giving statistically different values between the SMG and the QSO. I will discuss the results and a potential extension of this project using larger samples.

March 8: A galactic centre gravitational-wave beacon -- Odele Straub

In my first Tea Talk I will stay close to the tea theme and tell you how teapots and saucers are connected to the galactic centre. In other words, I will show with a back-of-the-envelope calculation, that the energy supply of a single star is sufficient to sustain a planetary mass in orbit around the central massive black hole and produce a long-lasting and strong gravitational-wave signal that can permeate the whole Galaxy. 

March 1: The Life Cycle of Star-forming Gas in Galaxies -- Andreas Schruba

Star formation in individual molecular clouds and whole galaxies is inefficient and we lack a good understanding why this is so. Observational and theoretical studies identify gas and galaxy dynamics, gas turbulence, and stellar and AGN feedback as key physical processes but we lack quantitative knowledge of timescales and efficiencies of the gas-star cycle. I have contributed to the formulation of a new statistical method that extracts these timescales and efficiencies from observations sampling molecular clouds and young stars across galaxies. In our first study, we apply this method to sensitive ALMA observations of the nearby, flocculent galaxy NGC 300 and find star formation to be fast and inefficient due to short-lived molecular clouds and rapid feedback (Nature, accepted). Next, we will study the gas-star cycle across 80 nearby galaxies across the star-forming main sequence observed by the PHANGS ALMA, MUSE, HST Large Programmes.

February 2019

February 22: Sub-pc dust structure and gas kinematics of a nearby AGN -- Jason Dexter

I’ll show preliminary GRAVITY AGN team results for the nearby Seyfert 1 NGC 3783. We see elongated and asymmetric dust structure at sub-mas scale with an orientation roughly matching that of the broad emission line velocity gradient. This suggests a common physical origin of the hot dust and ionized gas. It could either be a (counter-)rotating, flattened, equatorial structure or an extended radial outflow. 

February 15: No talk

February 8: No talk

February 1: What stellar orbit is needed to measure the spin of the Galactic Center black hole from astrometric data?  -- Idel Waisberg

One of the main goals of GRAVITY is to constrain the spin of SgrA*. Although that might be possible through flare astrometry, a cleaner measurement could rely on astrometric monitoring of a yet to be discovered inner star through Lense-Thirring precession. I will talk about the prospects of a spin detection with GRAVITY by combining simulations of relativistic stellar orbits with the known properties of the Galactic Center stellar cluster. How many stars are expected within the GRAVITY field of view? What is the chance that they could lead to a spin detection for a reasonable observing campaign? What is the role played by radial velocities in spin detection? 

January 2019

January 25: Hunting for fainter stars around SgrA*  -- Feng Gao

One of the main science goal for GRAVITY in the Galactic Center region is to find stars within the S2 orbit. In this tea talk, I will introduce the nature of this "source-detection" problem, summarize what we have done with the past two years of GRAVITY data, and speculate for the upcoming observations this year. 

January 18: The GRAVITY AGN Large Program -- Eckhard Sturm

December 2018

December 14: ERIS, the new instrument for the VLT on 2020 -- Ángela Cortes

I will describe the two instruments that are part of ERIS, and the different observing modes that they will offer, plus some details about the AO module and performance, to end up with the details on what we will change, at MPE on SPIFFI to get SPIFFIER.

December 6: The ISM properties of local analogs of high redshift Main Sequence Galaxies -- Alessandra Contursi

I will present the results of the analysis of PACS spectroscopy and photometry data of a sample of Lyman Break Analogs (LBAs). These are local galaxies that share many properties with the high redshift galaxies selected with the Lyman break technique. I will try to answer the question of whether these systems have ISM typical of galaxies above the local main sequence or rather of z~1-2 MS star forming galaxies.

November 2018:

November 30: No talk

November 23: Molecular outflows in nearby galaxies -- Dieter Lutz

November 2: No talk, day after holiday (All Saints' Day)

October 2018:

October 26: Gas Content and Star formation of Quasar Host Galaxies -- Jinyi Shangguan

The interstellar medium is crucial to understanding the physics of active galaxies and the coevolution between supermassive black holes and their host galaxies. The infrared spectral energy distribution (SED) provides abundant information of the dust and gas in different phases across the galaxy. With a newly developed Bayesian Markov Chain Monte Carlo fitting method, we decompose various overlapping contributions to the integrated SED, including starlight, warm dust from the torus, and cooler dust on galaxy scales. This procedure yields a robust dust mass, which we use to infer the gas mass, using a gas-to-dust ratio constrained by the host galaxy stellar mass.  Using this method, we find the low redshift quasars are not capable to blow the cold gas out of the host galaxy via the so-called "quasar mode" feedback, and study the star formation of starburst galaxies along the merger sequence.  I will briefly introduce some ongoing works using ALMA Compact Array to measure the CO emission in some quasar host galaxies, which may shed light on some future observations.

October 17: Getting out the most of SINFONI data and the Equivalence principle -- Felix Widmann

I will show the changes we did to the SINFONI data reduction and calibration and how they lead to better radial velocities. This helped us to, for example, test the Einstein Equivalence Principle around Sgr A*. I will show the results from this and shortly comment on other applications, as for example the search for binaries among the S-Stars.     

October 12: Molecular Outflows Near and Far  -- Rodrigo Herrera-Camus

October 5: Some submillimeter results on the Galactic center  -- Liu Hauyu (ESO)

I will (informally) present some of my previous and ongoing observational studies about the gaseous accretion flows towards the Galactic center, from 20 pc scales to few tens of AU scales. I will provide some of my opinions about how  potentially infrared and (sub)millimeter and radio observations are complementary with each other,  which I would be happy to discuss with the audience. 

September 2018:

September 28: PHIBSS1, 2 and Beyond... -- Linda Tacconi


I will summarize what we've learned from the IRAM PHIBSS surveys, and discuss the IR-group's plans for NOEMA^3D, our planned legacy program for the newly upgraded NOEMA. 


September 21: Next generation disk dynamics modeling -- Sedona Price

I will present an overview of Dysmalpy, an updated implementation of the disk modeling code DYSMAL. I will cover the available modeling options, show some example model fits, and touch on the ongoing/future options to be implemented. 

September 14: No Talk -- MPE Science Day this week

August - Sep 7: Summer Break

July 2018:

July 27: Galactic Winds at Cosmic Noon -- Natascha M. Förster Schreiber 

I will present the latest results from our studies of the demographics and properties of galactic outflows at z ~ 1 - 3, based on the KMOS^3D and SINS/zC-SINF IFU surveys. 

July 20: GeMS/GSAOI, Calibration of the optical distortion for an MCAO-fed imager -- Vincent Garrel

GeMS, the Gemini Multi-Conjugate Adaptive Optics (MCAO) System, is the first multi-sodium based Laser Guide Star (LGS) Adaptive Optics (AO) system used for astronomy. It delivers a uniform, close to diffraction- limited Near-Infrared (NIR) image over an extended FoV of 2arcminutes. The compensated images routinely show PSF in the K-band with Strehl Ratios (SR) in the 20% range and Full-Width Half Maximum (FWHM) less than 90 mas over a field of view of 85x85 arcsecond of the instrument GSAOI, Gemini South Adaptive Optics Imager. Due to the particular configuration of the pair, the optical distortion display a complex pattern and a fast temporal evolution, limiting its astrometric performance. I review the past and current effort to measure, model and provide a correction solution to astronomers.

July 13: No Talk - IR BBQ

July 6:  Interferometry in Astronomy - The GRAVITY Metrology System and Galaxy Evolution with the IRAM Interferometer -- Magdalena Lippa

Interferometry is a powerful tool in astronomy used for sky observations with increased spatial resolution and sensitivity. In my dissertation, I demonstrate these and other capabilities of interferometry using two leading world-class representatives of both the radio and optical regime, namely the IRAM interferometer and the GRAVITY instrument at the VLTI. GRAVITY observes two sky objects simultaneously at wavelengths of 2 µm. Measuring the differential optical path difference (dOPD) between both signals for pairs of telescopes provides the intrinsic phase of the science object as well as its angular separation to the reference target, known as phase-referenced imaging and narrow-angle astrometry. For this purpose, the internal dOPDs in the instrument and observatory need to be measured with nanometer accuracy. The laser metrology traces all the light paths from the GRAVITY spectrometers back to the telescopes.

The IRAM interferometer provided a first large statistical census of the molecular gas in distant galaxies at the peak of cosmic star formation. On this basis, I studied spatially resolved molecular gas in a small sample of galaxies. I compared the morphology of the molecular gas with the structures of stellar continuum, stellar mass and star-formation rate. Furthermore, I extracted the kinematics of the molecular gas. While similar studies are frequently done for the ionized-gas component on large statistical samples, the corresponding analysis of molecular gas is still rather rare.

June 2018:

June 29: The ALMA, MUSE, and SINFONI view of the circumnuclear region around the luminous AGN in NGC 5728  -- Taro Shimizu

AGN feedback seems to be a necessary ingredient in models of galaxy evolution to reproduce the population we observe today. Without AGN feedback, star formation in simulated galaxies runs wild and results in a large population of blue, star forming galaxies at z=0 while the addition of energy from an AGN successfully moderates the growth of galaxies and shuts down star formation. However, while successful in simulations, observations of AGN feedback in nature currently are limited and debate occurs over the precise physical processes that govern AGN feedback. In this talk, I will detail my recent work on a powerful local AGN in NGC 5728 for which I have combined observations from ALMA, MUSE, and SINFONI to study the circumnuclear region in depth. I will discuss the energetics and kinematics revealed from these observations that show evidence for a complex interplay between an AGN driven outflow and nuclear ring of star formation and what this suggests for the overall effect of AGN feedback in this singular galaxy.

June 22: (Another) Update on Galactic Center Observations -- Oliver Pfuhl

June 15: QFitsView: unde venis - quo vadis? -- Thomas Ott and Alex Agudo

A new shiny improved expanded upgraded version of QFitsView and dpuser will be released in the very near future. In this presentation we demonstrate some of the new features. We will also remind the audience of some not commonly known aspects of QFitsView.

June 7: What can we learn from GRAVITY astrometry of Sgr A* flares? -- Michael Bauböck 

The precision of GRAVITY is continuing to improve and approach the ~10s of Î¼as scale. This opens the possibility to obtain multiple astrometric measurements during a single infrared flare, allowing for a measurement of the possible motion of the source. This motion along with the corresponding lightcurve of the flare encodes information about both the accretion flow as well as the black hole itself. Measuring these properties depends on accurate models of the relativistic motion of material near the black hole as well as the lensing of photons as they escape to a distant observer. I will discuss our efforts to model the expected motion during IR flares and the degree to which we can expect to constrain the properties of Sgr A* using GRAVITY.

May 2018:

May 26:  Late-Type Stars around the Central Black Hole --  Maryam Habibi

Observations show a relative paucity of red giant stars within the central 0.5 pc in the Galactic Center (GC). By co-adding spectroscopic observation within 10 years, I identify five new late-type stars within the central 1 arcsecond 2 (0.02 pc× 0.2 pc) of the Galaxy. This finding increase the number of late-type stars to 21, of which I construct deep spectra of 15 stars. Ten of these stars are K0-K3III-type stars (T eff ∼ 4100 − 4600 K) consistent with 3-10 Gyr isochrones. The brightest late-type star in this region is a K3III star with 30 Rsun ,
providing a clue to stellar interactions proposed to remove the brightest giants in the region. Expanding the spectral-type-classification in the vicinity of Sgr A* down to 17.5 mag,
I re-address the search for the predicted stellar cusp around the Milky Way's central black hole. My preliminary results shows that the radial density distribution of this late-type stellar ‘‘cusp'’ follows a power law of exponent ~0.3 which is shallower than initially theoretically-predicted and steeper than previously suggested in observations. I also report on identifying the first five warm giants (G2-G8III) in this region, among which the star S20 is the warmest late-type star (G2III, T eff = 5550±54 K) detected in the central arcsecond, with a strong Brγ line and weak CO bandheads, only detectable in its combined spectrum with an S/N> 100.

May 18:  Unveiling the origin of gaps in protoplanetary disks via CO observations --  Stefano Facchini

High angular resolution observations of protoplanetary disks are showing a variety of sub-structures, where gaps and rings in particular seem to be a common feature shared by many systems. Until now, such structures have been detected in continuum, both in the (sub-)mm and in NIR scattered light maps, tracing the distribution of dust particles. A variety of models has been invoked to interpret the observations, ranging from embedded protoplanets to dust opacity variations at condensation fronts, and many other physical mechanisms. In this talk, I will show how observations of molecular lines with ALMA can distinguish between different scenarios. In the planetary hypothesis, simultaneous observations of thermal continuum and molecular lines can be used to infer the mass of the planets carving the observed gaps.

May 11:  No Talk (day after holiday)

May 4: Where do the spirals come from? A multi-wavelength, high-resolution study of HD135344b -- Paolo Cazzoletti

Recent observations of protoplanetary disks in both optical/near-infrared scattered light and (sub-)mm continuum emission have revealed complex structures such as spirals, rings and vortices in micron- sized and mm-sized respectively. Planets are often invoked as an explanation, but the number of planets and their location are degenerate, and the same system can often be explained by more than one scenario. Moreover, most of the time simulations are only able to reproduce the structures observed in one wavelength at the time, missing the information provided by differently sized dust grains. In fact, no clear connection between the structures observed in scattered light and mm has so far been found. HD135344B is a bright transition disk showing perfectly symmetrical spiral arms at near-IR and asymmetric structures at mm-wavelengths at the same time, and an ideal candidate to look for this missing connection. We present new 0.06” resolution ALMA Cycle 4 and 5 observations of this object in Band 3 (3 mm) and Band 4 (2 mm). A combination of these optically thin observations with our previous data at shorter wavelengths will allow a study the spectral index and the dust properties inside the asymmetry through a multi-wavelength analysis, and thus to determine whether or not dust is being trapped inside a massive vortex. Ultimately, we will be able to test whether the asymmetric structure is massive enough to launch the spiral arms observed at near-IR and if a single, massive inner planet is sufficient to explain micron and mm wavelength observations simultaneously, as proposed in van der Marel, Cazzoletti et al. 2016. 

April 2018:

April 27: Star Formation Driven Outflows at z~2.3 with the SINS-AO survey  -- Rebecca Davies

Star formation driven outflows are believed to play an important role in regulating the conversion of gas to stars,  particularly in galaxies below the Schechter mass. However, the relationship between the presence and velocity of outflows and the rate and concentration of star formation in galaxies is a topic of ongoing debate. We utilise the excellent spatial resolution of the SINFONI data from the SINS-AO survey to investigate the relationship between star formation activity and outflow properties on scales of 1-2 kpc in a sample of 25 galaxies at z~2.3. We find that outflows can be driven only when the local star formation surface density exceeds ~0.8 Msun/yr/kpc^2, and that the outflow velocity is positively correlated with the star formation surface density. The fastest outflows have velocities comparable to the galaxy escape  velocities, indicating that some of the outflowing material may penetrate into the galaxy halos. However, the mass loading factors are relatively low (0.1-0.3), suggesting that the ionized gas phase may constitute only a small fraction of the total mass in these outflows.     

April 20: Multiple Star Systems in the Orion Nebula -- Martina Karl

This work presents an interferometric study of the massive binary fraction in the Orion Trapezium Cluster with the novel GRAVITY instrument. It is the most comprehensive and most sensitive interferometric survey of the Trapezium Cluster to date. The resolution and sensitivity of GRAVITY allows resolving companions on scales of 2–200 milliarcseconds with a magnitude as faint as 10.6 mag (K-band), which corresponds to ∼1–100 AU and stellar masses as low as 1.6 M⊙ at the distance of Orion. We observed a total of 16 stars of mainly OB spectral type. We found four previously unknown companions for θ1 Ori B, θ2 Ori B, θ2 Ori C and NU Ori. We confirmed four more companions for θ1 Ori A, θ1 Ori C, θ1 Ori D, and θ2 Ori A, all with substantially improved astrometry and photometric mass estimates. We redefined the orbit of the eccentric high mass binary θ1 Ori C and we were able to derive a new orbit for θ1 Ori D. We found a system mass of 21.7 M⊙ and a period of 53 days. Together with previously detected other companions seen in spectroscopy or direct imaging, eleven of the 16 high mass stars are multiple systems. We obtained a total number of 22 companions. The companion fraction of the early B and O stars in our sample was about 2, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints towards a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also did not find a substantial population of twin binaries. The observed distribution of mass ratios declined steeply with mass, and like the direct star counts, indicates that our companions follow a more normal initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We excluded collision as a dominant formation mechanism but found no clear preference for core accretion or competitive accretion.         

April 13: Image-To-Image Transformations with Generative Adversarial Networks -- Philipp Plewa

Recently, Stark et al. ( have demonstrated a new approach for robust subtraction of AGN light from SDSS images of quasar host galaxies, using a generative adversarial network (GAN). I will briefly explain the main ideas behind this approach, and show how a similarly constructed GAN ( can be successfully employed to either subtract point sources from near-infrared images of the Galactic Center, to reveal the structure of gas filaments spread throughout the region, or to subtract the background emission and sharpen the images, to mitigate source confusion. For these tasks, the GAN requires neither a source catalog, nor a particularly accurate model of the point spread function, in contrast to other techniques. At the start of the talk, I will also present an overview of my other recent work on the Galactic Center, in one-slide summaries, focusing on the modeling of astrometric confusion noise (, efficient photometric stellar classification (, and the correction of image distortion (

April 6: X-Shooting SS 433 I. Baryonic Jet Energetics  -- Idel Waisberg

The X-ray binary SS 433 is the only known steady super-Eddington accretor in the Galaxy. It is also the first microquasar discovered, though the rapidly moving hydrogen and helium optical emission lines from its relativistic (0.26c), baryonic jets. Being the only known source of its kind, the conditions of the optical emitting gas in the jets and its heating mechanism are still an open question, and are thought to be related to radiative instabilities in the jet and its interaction with the surrounding disk wind outflow. I will present the first XSHOOTER observations of SS 433, which were a spin-off of our GRAVITY observations last summer. We use the up to twenty jet lines of hydrogen and helium per epoch to constrain the temperature, density and optical depth of the jet gas using the spectral synthesis code Cloudy. Doing so at different epochs allows us to study the evolution of the optical emitting gas as it travels through its surrounding medium. 

March 2018:

March 30: No Talk -- Good Friday

March 23: Structuring Molecular Gas from GMC to Galaxy Scale -- Andreas Schruba

March 16: Everything You Always Wanted To Know About Galaxy Quenching (But Were Afraid To Ask)  -- Sirio Belli

The physical mechanism responsible for shutting off star formation in galaxies (i.e., quenching) represents one of the most important open questions in the field of galaxy formation and evolution. In this talk I will review the physical processes that could be responsible for quenching, discussing the theoretical and observational evidence, with a focus on the quenching of massive galaxies in the early universe. 

March 9: MicroJy Radio Sources and Cosmic Evolution -- Dr. Bill Cotton (NRAO)

Counts of sources at cosmological distances as a function of flux density have long been used to infer the cosmic evolution of various classes of objects.  Counts of faint radio sources offer an extinction free measure of the high mass star formation in galaxies as well as AGNs.  Inspired by the ARCADE-2 CMB balloon experiment which detected an unexplained low frequency component which was postulated to be a previously unknown population of extragalactic sources, we began a series of deep surveys using the VLA at 2-4 GHz. The "confusion limited" technique allows measuring populations below the image noise and revealed the expected turnover in the counts of star forming galaxies but no hint of a new faint population to explain the ARCADE-2 data.  The source counts differed from some previous deep radio surveys which we postulate is due to incorrect corrections for source size. Our results are consistent with the same steep luminosity evolution for both AGNs and star forming galaxies. Using images made with different VLA configurations we have determined that the median size of 10-100 microJy sources is 0.3" and that this population is dominated by star forming galaxies at z~1; the effective size of the star forming region is ~1 kpc.  A strong correlation between radio and near IR flux densities suggests that when star formation is active, the rate is proportional to the total mass of the galaxy.

March 2:  Ionized and molecular kinematics of a z~1.4 galaxy -- Hannah Übler

February 2018:

February 23: TBD

February 16: Update on Galactic Center science -- Stefan Gillessen

February 9: Special talk: Results from a Joint IFU-Interferometric Survey: Molecular Gas in Nearby Galaxies through the EDGE-CALIFA Survey  - Dyas Utomo (Ohio State University)

Over the past few decades, increasingly powerful optical surveys of galaxies have been used to study the process of structure formation in the Universe. In particular, spectroscopic surveys have revealed clear trends in star formation, metal enrichment, stellar populations, and nuclear activity. However, large-scale spectroscopic surveys mostly neglect the internal structure of galaxies, which is the key to their evolution. An era of integral field unit (IFU) spectroscopy (e.g. CALIFA survey) is now upon us, providing simultaneous spectral and spatial coverage and resolution. These data allow us to map gas and stellar metallicities, ionized gas and stellar dynamics, star formation rates (SFRs), stellar mass densities, and ages. Coupling with the imaging spectroscopy of molecular gas from millimeter interferometers (e.g. EDGE survey), it offers a new window for studying baryon cycle in local galaxies. In this talk, I will presents the recent results and progress of the EDGE-CALIFA survey, especially the molecular gas-star formation relation, the comparison between CO and H-alpha rotation curve, and the local ISM properties at the supernovae sites.


February 2: CubeSats: an opportunity for astronomy, or just a toy for grown up? - Sylvestre Lacour

PicSat is a nanosatellite that was integrated by, and is operated by, the Paris observatory (no space agency, no big consortium). Its goal is to observe the transit of the giant planet beta Pictoris, expected to happen in 2018. After only three years of development, the satellite has been put into a 505 km Sun sunchronous orbit in January 2018 (PSLV C-40). I will present the project, and hopefully, we can discuss if the technology can be useful for our projects here. I’ll also talk about gravitational wave, if we have time.


January 2018:

January 26: Spectro-Interferometric Signatures of the Broad Line Regions in Active Galactic Nuclei - Raphael Stock


The sensitivity of GRAVITY allows ten microarcsecond precision spectro-astrometry (referencing spectral lines to the continuum), opening up the possibility to spatially resolve the broad line region (BLR) of AGNs for the first time. We develop a flexible phenomenological model of the BLR based on collections of optically thin, orbiting clouds. Comparing the model with GRAVITY data provides constraints on BLR structure and dynamics, as well as an independent method for measuring black hole mass.


January 19: No talk


January 12: Zooming in on planet-forming zones of disks around young stars - Ewine F. van Dishoeck


Protoplanetary disks are the birthplaces of planets but the spatial resolution at long wavelengths has so far been insufficient to resolve the critical 5-30 AU region. The Atacama Large Millimeter/submillimeter Array (ALMA) now allows us to zoom in to nearby disks and determine the physical and chemical structure associated with planet formation. This talk will provide examples of recent work on observations and models of protoplanetary disks in various stages of evolution. Surveys of large numbers of disks such as performed for Lupus provide insight into typical masses and sizes, revealing surprisingly weak gas emission. Does this imply low disk masses or is carbon missing?


December 2017:


December 22: Start of Winter Break


December 15: Accretion physics and Sgr A* - Dr. Jason Dexter


Let's talk about accretion onto Sgr A* and what we might learn in the next few years. Ideally this would be in the form of a group discussion, so please come prepared with questions at any level about accretion disks and jets, the Galactic center, Sgr A*, black holes, variability/flares, interferometry/GRAVITY, or related topics.


December 8: The natural emergence of the SFR-H2 surface density relation in galaxy simulations - Dr. Alessandro Lupi (IAP)


Recent developments of numerical techniques and sub-grid modelling have allowed to investigate in more detail the galaxy properties and the effect of star formation (SF), and stellar and AGN feedback, on the host evolution. In particular, several groups have started to employ H2-based SF prescriptions in numerical simulations, motivated by the observational evidence of a linear correlation between the star formation (SF) rate and the molecular hydrogen (H2) surface densities in nearby star-forming galaxies. However, recent theoretical studies have revealed a lack of causal connection between H2 and SF, suggesting that the formation of H2 could be controlled by SF and not vice versa. I will present a new sub-grid model, implemented in the meshless code GIZMO, to follow the formation and dissociation of H2, via the chemistry package KROME, including gas and dust shielding, self-shielding of molecular gas, SF, supernova feedback, and extragalactic and local stellar radiation (modelled both as a sub-grid model and with on-the-fly radiative transfer calculations).
I will discuss the results of a suite of simulations of an isolated gas-rich galaxy at z=3, showing how it can naturally reproduce at the same time the Schmidt-Kennicutt law for total gas (HI+H2) the SF-H2 correlation, without any a priori dependence of SF on the H2 abundance. I will finally present, as one possible application of the model, a study of the the kinematics and dynamics of molecular gas in high-redshift quasars.


December 1: Update on NOEMA - Prof. Reinhard Genzel


November 2017:

November 24: No talk

Novermber 17: No talk - Ringberg IR Group Retreat

October 2017:

October 27: BAT AGN prefer circumnuclear star formation - Dr. Dieter Lutz

October 20: Local Luminous AGN with Matched Analogs (LLAMA): Nuclear stellar properties of Swift BAT AGN and matched inactive galaxies - Dr. Ming-Yi Lin

In a complete sample of local 14-195 keV selected AGNs and inactive galaxies, matched by their host galaxy properties, we study the spatially resolved stellar kinematics and luminosity distributions at near-infrared wavelengths on scales of 10-150 pc, using SINFONI on the VLT. In this paper, we present the first half of the sample, which comprises 13 galaxies, 8 AGNs and 5 inactive galaxies. The stellar velocity fields show a disk-like rotating pattern, for which the kinematic position angle is in agreement with the photometric position angle obtained from large scale images. For this set of galaxies, the stellar surface brightness of the inactive galaxy sample is generally comparable to the matched sample of AGN but extends to lower surface brightness. After removal of the bulge contribution, we find a nuclear stellar light excess with an extended nuclear disk structure, and which exhibits a size-luminosity relation. While we expect the excess luminosity to be associated with a dynamically cooler young stellar population, we do not typically see a matching drop in dispersion. This may be because these galaxies have pseudo-bulges in which the intrinsic dispersion increases towards the centre. And although the young stars may have an impact in the observed kinematics, their fraction is too small to dominate over the bulge and compensate the increase in dispersion at small radii, so no dispersion drop is seen. Finally, we find no evidence for a difference in the stellar kinematics and nuclear stellar luminosity excess between these active and inactive galaxies.

October 13:   Kinematic and structural evolution of star-forming galaxies at 1.4≤z≤3.8 with MOSDEF & CANDELS  - Dr. Sedona Price

I will present preliminary results on the kinematics and masses of star-forming galaxies at “cosmic noon” (z~1.5-3) using the MOSDEF (MOSFIRE Deep Evolution Field) Survey. Using the MOSDEF observations together with CANDELS imaging and multiband photometry, we examine how masses, structures, and inferred dark matter fractions vary across the galaxy population and over time.     

October 6: No Talk

September 2017:

September 29:  Flame: A Flexible Data Reduction Pipeline for Near-Infrared and Optical Spectroscopy - Dr. Sirio Belli

Flame is a pipeline for reducing spectroscopic observations obtained with multi-slit near-infrared and optical instruments. Because of its flexible design, Flame can be easily applied to data obtained with a wide variety of spectrographs. I will illustrate the pipeline by showing an example of data reduction for a near-infrared instrument (LUCI at the Large Binocular Telescope) and an optical one (LRIS at the Keck telescope).

 September 22: SHINING: A Survey of Far-Infrared Fine-Structure Lines, from Resolved Star-Forming Galaxies and Active Galactic Nuclei to Ultraluminous Infrared Galaxies - Dr. Rodrigo Herrera-Camus



July 2017:

July 14: No Talk - Start of Summer Break

July 7: Dusty spirals triggered by shadows in protoplanetary disks - Dr. Nicolás Cuello (PUC)

Spirals waves form in protoplanetary disks (PPDs) around young stars due to different physical mechanisms: planet torques, gravitational perturbations and illumination effects. Although recent near-infrared and sub-millimetric observations revealed astonishing spiral-shaped features in PPDs, there is an active discussion to understand how they formed. Regardless of their origin, spirals are characterized by a local increase in pressure, which translates into radial and azimuthal asymmetries in the gas and in the dust distribution. In this work, we focus on the spirals formed in the gaseous phase due to shadows cast at fixed disk locations, as in Montesinos et al. 2016. During this talk, we will discuss how these spirals affect dust dynamics and planet formation in the disk. Also, we will show what are the observational signatures of the dusty spirals obtained. Finally, we will show how ALMA could observe them at millimetric wavelengths.

June 2017:

June 30: Twelve years of spectroscopic monitoring in the Galactic Center: the closest look at S-stars near the black hole - Dr. Mariam Habibi

I will present our study of young S-stars wiythin a distance of 0.04 pc from the supermassive black hole in the center of our Galaxy. Given how inhospitable the region is for star formation, their presence is more puzzling the younger we estimate their ages. By co-adding the result of 12 years (2004-2016) of high resolution spectroscopy within the central arcsecond, we have obtained high signal to noise H- and K-band spectra of eight stars orbiting the central supermassive black hole. Using deep H-band spectra, we show that these stars must be high surface gravity (dwarf) stars. We compare these deep spectra to detailed model atmospheres to infer the stellar parameters. The inferred masses lie within 8--14$M_\odot$. We derive an age of $6.6^{+3.4 }_{-4.7}$ Myr for the star S2, which is compatible with the age of the clockwise rotating young stellar disk in the GC. We estimate the age of all other studied S-stars to be less than 15 Myr, which are compatible with the age of S2 within the uncertainties. The relatively low ages for all S-stars we have investigated favor a scenario in which the stars formed in a local disk rather than the field-binary-disruption scenario throughout a longer period of time.


June 23: No talk

June 16: Holiday

June 9: Update on Outflows Projects - Dr. Eckhard Sturm

June 2: The Physical State of the Cold Gas and Star Formation Process in Nearby Galaxies - Dr. Andreas Schruba

A key challenge for current star formation studies is to link the detailed view of the star formation process within individual Galactic molecular clouds to the kpc-scale and galaxy-wide trends described by extragalactic work. I will highlight recent progress in observing the cold gas in nearby galaxies, focussing on new results from large programs at millimeter and radio wavelengths to observe the overall atomic and molecular gas reservoir in galaxies at cloud-scale resolution, and to probe the gas at higher densities with multi-line spectroscopy. The picture that emerges from these studies is that the conversion of cold gas into young stars depends on galactic environment: gas at a particular density does not appear to form stars in a universal way.

May 2017:

May 26: Impact of Faraday effects on polarisation  - Alejandra Jimenez Rosales

At the centre of our galaxy lies a supermassive black hole, Sagittarius A* (Sgr A*). Mm-VLBI observations made with the Event Horizon Telescope (EHT) have spatially resolved a linear polarisation fraction (LPF).
The present work studies the impact of Faraday effects (rotation and conversion) on the measured LPF. Considering a model with accretion from a magnetised disk onto a black hole, we post-process GRMHD simulations tied to the observed sub-millimetre flux observed in Sgr A* and perform a fully relativistic radiative transfer calculation of the emitted synchrotron radiation. We obtain polarised images and, by comparing the scrambled vs. the coherent, we characterise their degree of change, which we call the ‘correlation length’ of the image. We show how measurements of the polarised correlation length could constrain the strength of these effects, and, consequentially, plasma properties like electron temperature and magnetic energy fraction

May 19: JWST-MIRI: getting ready for launch - Dr. Ewine van Dishoeck

This talk will give a brief overview of the JWST project and the MIRI instrument in particular. Preparations for GTO, GO and Early Release Science (ERS) science are in full swing and galactic science plans will be discussed.

May 12: KMOS-3D reveals Halpha emission in high-redshift quiescent galaxies  - Dr. Sirio Belli

I will present a study of emission lines in the quiescent galaxies targeted by the KMOS-3D survey. We detect line emission in about 20% of the 120 quiescent galaxies observed. Nine of these objects have low [NII]/Halpha ratio, consistent with low-level star formation activity. The presence of satellites and the low inferred gas metallicity suggest that these quiescent galaxies are accreting fresh gas from minor mergers or gas inflows. Finally, by analizing the spatially resolved emission lines we find evidence for rotation in about half of the nine targets. This rare population represents an important link between gas-poor quiescent galaxies and their progenitors, the star-forming massive disks.

May 5: How the role of environment in fuelling AGN depends on the host galaxy  - Dr. Ric Davies

I will show that the fraction of local AGN in S0 hosts decreases strongly as a function of galaxy group size or halo mass; but that this is not the case for AGN in spiral hosts (which, because most AGN are found in spiral galaxies, dilutes the signature of environmental dependence for the population as a whole). The difference is due to the source of gas and so should also impact the AGN luminosity function, duty cycle, and obscuration. Indeed, there is a significant difference in the luminosity function for AGN in spiral and S0 galaxies, and tentative evidence for some difference in the fraction of obscured AGN. 

April 2017:

April 28: The detection of Sgr A* in the far infrared HERSCHEL/PACS 2012 March Campaign - Sebastiano von Fellenberg

Following a dedicated reduction process, a significant increase of flux could be measured during one night in March 2012. I will present the reduction steps necessary to remove artifacts and systematics present in the standard pipeline product. 

April 21: Gas dynamics and extended x-ray emission from the Galactic Centre - Dr. Jorge Cuadra (PUC)

Abstract: I will present numerical models of the gas dynamics in the inner parsec of the Galactic centre. We follow the gas from its origin as stellar winds of around 30 observed young massive stars, until it is either captured by the central black hole, or leaves the region. I will show how comparing the simulations with recent Chandra observations  confirms the origin of the gas in stellar winds, and constrains the properties of Sgr A* outflows during the last few hundred years.

April 14: Holiday

April 7: No talk

March 2017:

March 24: Spatially resolved star formation at z=1: molecular gas & stars - Magdalena Lippa

Cosmic star formation went through a peak close to redshift z=1 and since then has been decreasing. While there are many observational studies which analyze the ionized gas in star-forming galaxies in great detail at this epoch, spatially resolved molecular studies are still rather rare. In the work presented here I perform a respective analysis on sub-galactic scales looking at the main players of star formation: molecular gas and stars. The sample of five massive star-forming galaxies taken from the PHIBSS surveys shows clumpy morphologies in both these components. The light of the bulk stellar component in the centers of galaxies retrieved from SED fitting of rest-frame UV/optical photometry is highly extincted. Bright clumps off these centers show star-forming regions with comparably low visual extinction. These are findings already reported in literature. But what abou the gas? Imaging spectroscopy performed by the IRAM interferometer reveals that the molecular gas is rotating and turbulent at the same time as already shown for the ionized gas at similar redshifts. Dynamical modeling can help to get a handle on intrinsic properties measured by the kinematics such as dynamical mass and intrinsic velocity dispersion. However, constraining the various parameters of such models, especially galaxy orientation, can be a science on its own. For this reason I would like to share and discuss my findings with you.

March 17: Infalling clouds onto massive black hole binaries - Felipe Garrido (PUC)

Gas accretion is thought to be important for the dynamical evolution of massive black hole binaries, although the mechanisms that drive material to the galactic nuclei are poorly constrained. One plausible source of the gaseous fuel is clumps of gas formed due to turbulence and gravitational instabilities in the interstellar medium that later fall towards and interact with the binary. In this context, I present a suite of SPH simulations to study the evolution of turbulent gas clouds as they infall towards equal-mass, circular MBH binaries. I study the formation of gaseous structures and their dynamics, as well as the the feeding rate onto the MBHs depending on the different configurations, and show that some of the variabilities can have implications in the observability of these systems. I additionally study the dynamical evolution of the binary orbit during the interaction with different clouds and show that is dominated by the exchange of angular momentum through gas accretion during the first stages of the interaction for all orbital configurations. Building on these results, I construct a simple model for evolving a MBHB interacting with a sequence of clouds, which are randomly drawn from reasonable populations with different levels of anisotropy. In this scenario the binary efficiently evolves down to the gravitational wave regime, overcoming the "final parsec".

March 10: The Evolution of the Tully-Fisher Relation between z~2.3 and z~0.9 with KMOS^3D - Hannah Übler

We investigate the stellar mass and baryonic mass Tully-Fisher relations (TFRs) of massive star-forming disk galaxies at redshift z~2.3 and z~0.9 as part of the KMOS^3D integral field spectroscopy survey. Our spatially resolved data allow reliable modelling of individual galaxies, including the effect of pressure support on the inferred gravitational potential. At fixed circular velocity, we find higher baryonic masses and similar stellar masses at z~2.3 as compared to z~0.9. Together with the decreasing gas-to-stellar mass ratios with decreasing redshift, this implies that the contribution of dark matter to the dynamical mass at the galaxy scale increases towards lower redshift. A comparison to local relations reveals a negative evolution of the stellar and baryonic TFR zero-points from z=0 to z~0.9, but a positive evolution of the baryonic TFR zero-point from z~0.9 to z~2.3. We discuss a toy model of disk galaxy evolution to explain the observed, non-monotonic TFR evolution, taking into account the empirically motivated redshift dependencies of galactic gas fractions, and of the relative amount of baryons to dark matter on the galaxy and halo scales.


March 3: CN Fluxes and Rings in Plotoplanetary Rings - Paolo Cazzoletti

The bright emission of the CN molecule has been readily  observed in protoplanetary disk in the last 20 years with single dish observations. With the advent of modern interferometers, we are now able  to spatially resolve CN emission, which often shows ring-like structures. We investigate if such structures are due to the morphology  of the disk itself or if they are instead an intrinsic feature of the  emission of CN. With the help of the 2D thermochemical code DALI, we run  a set of disk models for different stellar spectra, masses and physical structures, and by using a chemical network accounting for the most  relevant CN reactions. We find that ring-shaped emission is a common feature of all the models we adopted: the highest abundance is found in the outer regions, the column density always peaks at 50-70 AU, and the  emission profile follows the column density. Higher mass disks therefore generally show brighter CN. We also find a strong dependence of the ring
brightness and location on the UV field, and in general that higher UV fluxes on the disk result in brighter and larger rings. This is for example what happens when the UV radiation impinging on the disk increases because of a higher disk flaring. These trends are due to the fact that the main path for the formation of CN relies on the existence in the disk of excited H2* molecules, which is formed through FUV pumping of the H2 molecules. The strong bond between FUV flux and CN emission and morphology could therefore provide critical information on the physical structure of the disk and on the distribution of dust grains (which affects the UV penetration), and could help to break some degeneracies in the SED fitting. Recent observations of other PDR tracers such as C2H and C3H2 also show a ring-shaped emission which is likely related to dust settling and to C and O depletion. A comparison between these molecules and CN will be made.

Febuary 2017:

February 24: The on-sky performance of the CIAO wavefront sensors and implications for GRAVITY performance - Dr. Casey Deen

I will give a brief overview of the CIAO wavefront sensors which currently inhabit the Coudé rooms of the Unit Telescopes on Cerro Paranal.  I will discuss the results of the commissioning activities for the CIAO units, standalone performance on sky, and the performance of GRAVITY when fed by CIAO.

February 17: Sub-milliarcsecond Optical Interferometry of HMXBs with VLTI/GRAVITY: The cases of BP Cru and SS 433 - Idel Waisberg

GRAVITY has opened a new window in the study of High-mass X-ray Binary (HMXB) systems by allowing spectral differential interferometry at high resolution for fainter targets. In this talk, I will present the results for two of these systems: BP Cru and SS 433. The first one consists of a slowly-rotating neutron star accreting from its blue hypergiant companion. Interferometry shows evidence for a distorted stellar wind and a long-predicted accretion stream. The second one consists of a compact object (most likely a black hole) accreting super-critically from its companion, with super-Eddington outflow in the form of accretion disk winds and collimated relativistic jets that show remarkable optical line emission. GRAVITY has allowed to spatially resolve the optical jet lines in this system for the first time, as well as the circumstellar wind environment probed by the stationary lines. I will conclude with the potential of upcoming multi-instrument observation plans for these objects.

February 10: A Massive Binary System can Feed Sgr A* - Diego Calderón (PUC, Chile)

The enigmatic G2 cloud just passed pericentre around the Galactic Centre super-massive black hole, Sgr A*. Despite all theoretical and observational efforts, its nature remains unclear. If purely gaseous, it is possible to explain it as a gas clump formed in a colliding wind binary. Here we study the hypothesis of G2 being one of such clumps ejected from the massive binary IRS 16SW. 

February 3: The interplay between dust and gas in protoplanetary disks - Dr. Stefano Facchini

The high sensitivity and angular resolution of ALMA are providing new insights on the typical properties of protoplanetary disks. A key parameter governing the secular evolution of disks is their outer radius. Interestingly, ALMA observations confirm earlier indications that there is a clear difference between the dust and gas radial extents. The origin of this difference is still debated, with both radial drift of the dust and optical depth effects suggested in the literature. In thermo-chemical models of protoplanetary disks, the dust properties are usually prescribed by simple parametrisations. In this work, the feedback of more realistic dust particle distributions onto the gas chemistry and molecular emissivity is investigated, with a particular focus on CO isotopologues. We take into account how dust surface area and density influence the disk thermal structure, molecular abundances and excitation. We show that the difference of dust and gas radial sizes is largely due to differences in the optical depth of CO lines and millimeter continuum, without the need to invoke radial drift. The effect of radial drift is primarily visible in the sharp outer edge of the continuum intensity profile. The gas outer radius probed by 12CO emission can easily differ by a factor of 2 between the models for a turbulent α ranging between typical values, with the ratio of the CO and mm radius increasing with turbulence. Grain growth and settling concur in thermally decoupling the gas and dust components, due to the low collision rate with large grains. As a result, the gas can be much colder than the dust at intermediate heights, reducing the CO excitation and emission, especially for low turbulence values. Interestingly, the low thermal coupling is expected to arise also in the dust cavity of large transition disks, or in the dust gaps recently observed at high angular resolution. A proper treatment of the thermal structure is fundamental to infer the properties of the purported planets invoked in some of these systems.

January 2017

January 27: Canceled - Dr. Annemieke Janssen

January 20: No Talk

January 13: The Post-Pericenter Evolution of G2 - Philipp Plewa 

We report on the evolution of G2 in the immediate aftermath of its recent pericenter passage, revealed by deep observations obtained in 2015 and 2016 using SINFONI and NACO at the VLT. Putting these new data sets in the context of our previous observations allows us to draw the most comprehensive picture of G2 to date and establish a number of key observational facts. On this basis we discuss the unique opportunity of using G2 as a probe of the inner accretion zone around Sgr A*, as well as implications for the nature, origin and fate of G2. 

January 6: No talk - Winter break

December 2016

December 23 & 30: No talk - Winter break

December 16: An Update on Monitoring Stellar Orbits in the Galactic Center - Dr. Stefan Gillessen 

Using 25 years of data from uninterrupted monitoring of stellar orbits in the Galactic Center, we present an update of the main results from this unique data set: A measurement of mass of and distance to Sgr A*. Our progress is not only due to the eight year increase in time base, but also due to the improved definition of the coordinate system. The star S2 continues to yield the best constraints on the mass of and distance to Sgr A*; the statistical errors of 0.13×10^6 M_sun and 0.12 kpc have halved compared to the previous study. The S2 orbit fit is robust and does not need any prior information. Using coordinate system priors, also the star S1 yields tight constraints on mass and distance. For a combined orbit fit, we use 17 stars, which yields our current best estimates for mass and distance: M = 4.28±0.10|stat. ±0.21|sys ×106 M_sun and R0 = 8.32±0.07|stat. ±0.14|sys kpc. These numbers are in agreement with the recent determination of R0 from the statistical cluster parallax. The positions of the mass, of the near-infrared flares from Sgr A* and of the radio source Sgr A* agree to within 1 mas. In total, we have determined orbits for 40 stars so far, a sample which consists of 32 stars with randomly oriented orbits and a thermal eccentricity distribution, plus eight stars for which we can explicitly show that they are members of the clockwise disk of young stars, and which have lower eccentricity orbits.

December 16: No talk

December 2:   The Spatial Distribution of Star Formation in Galaxies: Observing the Emergence of Galactic structure   Dr. Erica Nelson 

Imaging surveys with HST and kinematic surveys with KMOS have demonstrated that the structure of many galaxies is emerging at z~1. Key to understanding this process is a high resolution measurement of the distribution of star formation within galaxies. In this talk, I will describe my PhD thesis work studying the emergence of galactic structure using the spatial distribution of star formation in galaxies. This work uses WFC3 grism capability on HST which provides Hα maps of all galaxies at 0.7<z<1.5 in its field of view. Using Hα maps for 2676 galaxies, I will show where star formation is distributed in galaxies across the star formation - mass plane (the “main sequence”) placing constraints on both the mechanisms for enhancing and quenching star formation as well as on how the structure of galaxies is built.

November 2016

November 25:  The Connection Between Star Formation and AGN Activity in the Local Universe - Dr. Taro Shimizu 

Most theoretical models and cosmological simulations rely on some form of AGN feedback to slow or stop star formation in massive  galaxies and reproduce the local stellar mass function. I will present my work focusing on a Herschel survey of a relatively unbiased sample of  AGN at z~0 where I measured the star-forming properties using the  far-infrared SED. I find that while a comparison to a mass-matched sample of non-AGN galaxies indicates higher SFRs, AGN host galaxies seem to prefer a region on the SFR-stellar mass diagram in transition between the star-forming and quenched populations. I will further discuss the differences between Type 1 and Type 2 AGN and our recent VLA 22 GHz survey to try and spatially resolve the circumnuclear star formation and test the FIR-radio correlation.

November 18: Advanced Deconvolution of SINFONI Spectral Data Cubes   -  Stefan Schmalzl 

I present advanced techniques for spectral image deconvolution conducted in my master thesis. I worked on a deconvolution approach called Myopic deconvolution which tries to approximate the object as well as the PSF simultaneously. The focus lies on a mathematical formulation via linear algebra, embedded in a Maximum Likelihood or Maximum a Posteriori framework with different priors on the object and the PSF. As a result, deconvolution becomes an optimization problem which could be evaluated by a very efficient scaled gradient projection method. 

November 11: No Tea talk

November 4: No Tea Talk - Ringberg Galaxy Evolution Meeting

October 2016

October 28: ASTE CO(3-2) survey for nearby merging galaxies & ALMA band 3 line survey towards late stage merging galaxy NGC3256 - Tomonari Michiyama (NAOJ, SOKENDAI)

I review the Michiyama et al. 2016 (, which investigate the relation between the CO(3–2) luminosity and the far Infrared luminosity a sample of 29 early stage and 31 late stage merging galaxies, and 28 nearby isolated spiral galaxies. We find that normal isolated spiral galaxies and merging galaxies have different slopes (α) in the log ′CO(3−2)-logLFIR plane (α ∼ 0.79 for spirals and ∼ 1.12 for mergers). Comparing our results with sub-kpc scale local star formation and global star-burst activity in the high-z Universe, we find deviations from the linear relationship in the logL′CO(3−2)-logLFIR plane for the late stage mergers and high-z star forming galaxies. 

If I have time, I quickly introduce our recent  ALMA Cycle 3 results of molecular line survey towards a late stage merging galaxy NGC3256. We have detected 24 molecules at 2” angular resolution, which is high enough to resolve the double nuclei.

October 21: Pulse Profiles from Spinning Neutron Stars - Dr. Michael Bauböck

I will discuss efforts to model pulse profiles arising from hotspots on spinning neutron stars. These pulse profiles provide one of the most promising avenues for measuring neutron-star properties and constraining the equation of state of cold nuclear matter. I will describe current and future work to understand the physical effects that influence pulse profile shapes.  

October 14: Gaussian Processes for Bayesian Parameter Estimation - Philipp Plewa

Noise matters but is never known exactly, so we have to model it. In this whiteboard talk I will introduce the fundamentals of Gaussian Processes, which make it possible to model real world (correlated) noise in many situations.

October 7: The Kinematics of High-Redshift Quiescent Galaxies - Dr. Sirio Belli

I will present the recent results of a deep spectroscopic survey of quiescent galaxies at 1 < z < 2.5 carried out at Keck using the LRIS and MOSFIRE instruments. I will discuss the galaxy kinematics focusing in particular on the importance of rotational support for early quiescent galaxies, and the implications for galaxy evolution models.


Summer Break - No talks

July 2016

July 29: No talk - Start of Summer Break

July 22: A brief description of new results on the dynamics and chemistry of galactic and extragalactic ISM - Dr. Thomas Bisbas

In this tea talk I will present results of four different on-going projects examining the dynamics and chemistry of ISM. I will discuss about the role played by cosmic rays in tracing H2 gas in galaxies and I will show new 3D simulations of how CO is effectively converted to CI and CII by increasing the cosmic-ray ionization rate while the H2 molecule remains unaffected. I will present newly published ACA observations of NGC253 comparing CO(1-0) versus CI(1-0) ratio emissions and how they compare with the corresponding Milky Way values. I will further go through an extended study of CII emission from different environments and try to tackle the long standing question "where does your CII emission come from?". Finally I will show results of the StarBench code-comparison project on expanding HII regions and I will present a new analytical equation that describes the entire D-type phase with an error of less than 1% at all times when compared to high-resolution simulations. 

July 15: Mrk 231: The Nearest Laboratory to Study Quasar Feedback in Action, Slim Accretion Disks, but not Binary Black Holes - Prof. Sylvain Veilleux (University of Maryland) 

At a distance of only 178 Mpc, Mrk 231 is the nearest quasar known. In recent years, Mrk 231 has become the archetype of galactic-scale quasar-driven winds. These outflow events are purported to self-regulate the growth of the black hole (BH) and spheroidal component of the galaxy and explain the relatively tight BH-spheroid mass relation. In this presentation, I will first summarize the latest evidence for quasar feedback in action in this system. Next, I will present new ultraviolet HST spectra suggesting that Mrk 231 is also the nearest example of weak-lined "wind-dominated" quasars with high Eddington ratios and geometrically thick ("slim") accretion disks. I will argue that these data are inconsistent with the recently proposed binary black hole model. 

July 8: No talk

July 1: No talk - Fachbeirat

June 2016

June 24:  Structure and Evolution of Protoplanetary Disks - Paolo Cazzoletti

A large diversity of exoplanetary systems has been found, but it is still unclear what drives this diversity. Planets are formed in disks around young stars, but the sensitivity and resolution of pre-ALMA data have allowed only a handful of disks to be characterized, usually only in the dust. ALMA has opened up the possibility to survey hundreds of disks in both the gas and dust, and to also spatially resolve them. From initial ALMA surveys (e.g. in the Lupus cloud), it is already clear that gas and dust have very different distributions and also evolve differently. Morphologies also depend on the tracer: CO generally shows smooth distributions, CN shows ring-like structures and dust emission often shows very asymmetric structures. During my PhD I will focus on the different gas and dust structures, looking for possible connections and common origins. I worked on the modelling of CN emission, showing that a ring-like emission is an intrinsic feature of this molecule. In addition to this, I worked on ALMA Band 7 data of the HD135344B system, looking for a connection between the spiral arms observed in scattered light and the mm-sized dust distribution.

June 17: Practice Talks - New seminar room 

June 10: Evidence for a large trans-Kuiper-Belt planet? - Dr. Thomas Müller  

Computer simulations and observations of distant objects in our solar system indicate the presence of another, so far undiscovered planet.  I'll present a closer look at the trans-Neptunian region, the indications for a gravitational influence of planet IX, and possibilities to find it (or not). 

June 3: A single HII region model of strong interstellar scattering towards the Galactic Center - Egid Sicheneder

Free electrons along the line of sight broaden the radio image of Sgr A*. For a long time, this strong interstellar scattering was thought to be local to the Galactic Center, explaining the absence of pulsars (Cordes+2002). The observation of radio pulses from a recently detected magnetar near Sgr A* contradicts this explanation (Spitler+2014). We show that a single HII region 1.5-3.5 kpc away from Earth, with ne ~ 100-200 cm-3, R ~ 3-5 pc, can explain the observed angular broadening and pulse time delay. For a magnetic field strength of 10-45 μG, the rotation measure, previously thought to come from hot gas in the Galactic center, can instead originate in a cloud along the line of sight. Furthermore, we predict that sources within ~10 pc should be scattered by this HII region, while other known GC pulsars at larger separations > 20 pc should not.

May 2016

May 27: No talk

May 20: Thick Disks, and an Outflow, of Dense Gas in the Nuclei of Nearby Seyfert Galaxies - Ming-Yi Lin

We discuss the dense molecular gas in central regions of nearby Seyfert galaxies, and report arcsec resolution observations of HCN(1-0) and HCO+(1-0) for 3 objects. In NGC3079 the lines show complex profiles as a result of self-absorption and saturated continuum absorption. H13CN reveals the continuum absorption profile, with a peak close to the galaxy’s systemic velocity that traces disk rotation, and a second feature with a blue wing extending to −350 km/s that most likely traces a nuclear outflow. The morphological and spectral properties of the emission lines allow us to constrain the dense gas dynamics. We combine our kinematic analysis for these 3 objects, with a previous comparable analysis of 4 other objects, to create a sample of 8 Seyferts. In 7 of these, the emission line kinematics imply thick disk structures on radial scales of ~100 pc, suggesting such structures are a common occurrence. We find a relation between the circumnuclear L_HCN and M_dyn that can be explained by a gas fraction of 10% and a conversion factor αHCN ~ 10 between gas mass and HCN luminosity. Finally, adopting a different perspective to probe the physical properties of the gas around AGN, we report on an analysis of molecular line ratios which indicates that the clouds in this region are not self-gravitating.

May 13: Science discussion with Prof. C. Martin (Caltech)

May 6: No talk

April 2016

April 29:  The ISM at High Resolution in Local Galaxies - Dr. Andreas Schruba

State-of-the-art instruments like, ALMA, NOEMA, JVLA, and VLT/MUSE are revolutionizing our view on the ISM structure and star formation process in nearby galaxies. I will showcase  our ongoing observational efforts to obtain high physical resolution mapping and sensitive spectroscopy across the nearby galaxy population. These observations supersede previous single-dish surveys by more than an order of magnitude in resolution and sensitivity and allow for the first time to systematically study the physical state of the ISM, its dependence on local environments, and influence on the star formation process at the scales of individual molecular clouds. We see a strong dependence of the cloud-scale ISM properties (surface density, turbulent line width, and apparent gravitational boundedness) on environment. New, sensitive spectroscopy of faint high dipole moment lines (HCN, HCO+, HNC, CS) across large areas also reveals strong, physically driven dependences of gas density on environment. Finally, these changing physical conditions seem to define the ability of the gas to form stars. I will highlight our efforts to extract the underlying physical drivers for the variations and showcase how these provide stringent tests for theories of star formation.

April 22:  Blue Compact Dwarf Galaxies (BCDs): Can of Worms or Pandora Box - Dr. Vanessa Doublier Pritchard 

First a quick reminder: BCDs are star busting dwarf galaxies: i.e. they are:1- low mass (DM haloes < 10^9.5 Msol) 2- very gas rich (Mstar/Mgas< 0.1) 3- the champion of star formation rate "efficiencies" (10^-10 < sSFR < 10^-8/yr, as a comparison current sSFR for Arp 220 is ~2x10^-8 /yr), 4- they still manage to appear as young" with z<20% solar, 5- very low dust content, BUT very bright PDRs finally 6- always a significant fraction of the stellar mass made of pre- (or very soon  after post-) re-ionisation stars. But, lets face it, these Blue Compact Dwarf galaxies are either  ignored/dismissed or making astronomers/physicists' life very hard when one gives it a go at understanding their properties in details. They  don't behave like normal galaxies: they refuse to be "too small to not  fail" re-ionisation shutdown, make a mess of fundamental relations and refuse to be either young or old. In this small talk, I will mostly lay down some questions and propose  some leads to answer them. I will focus on metallicity and why the  fundamental importance of this observable needs to be assessed, on dust-molecular gas contents and why this is a quick-sand subject and finally address some troubling matters about modelisations both at large scales and at small scales. Finally, I will stress and hope to impress  upon the real need to bridge a gap between extra-galactic and galactic  research to tackle the faint/low-mass end of the galaxy luminosity/mass distribution.

April 15: No talk

April 8:   Tracing high-z galaxy kinematics from turbulent disks to quenched spheroids .- Dr. Emily Wisnioski 

The representative selection and depth of the KMOS3D Survey, an integral field survey of over 600 galaxies at z=0.7-2.7 using KMOS at the VLT, has allowed us to study in unprecedented detail rare galaxies at z>1 that may be in the process of quenching. The short timescales associated with the quenching process make it difficult to catch galaxies in the act of shutting down their star formation. Compact star-forming galaxies, making-up ~7% of our sample, are selected to have properties aligned with already quenched galaxies at the same or lower redshifts, e.g. stellar mass, density, and sizes, but forming stars at rates 2-10x higher. We measure resolved kinematics of ~30 of these galaxies within the KMOS3D survey. Our results - the first resolved spectral data of such objects - show that compact star-forming galaxies are rotationally-dominated systems, providing strong evidence that recently quenched galaxies at these epochs are likely to be "fast rotators". The majority of compact star-forming galaxies show evidence that they host an active galactic nuclei indicative of secular quenching processes.

April 1:   Lifecycle of interstellar grains in numerical simulations of GMC evolution .- Dr. Svitlana Zhukovska (MPA)

I will present a three-dimensional model of dust evolution based on numerical hydrodynamic simulations of the giant molecular clouds in a Milky Way-like galaxy. Our approach includes destruction by interstellar shocks and dust mass growth through gas-grain interactions in the ISM. The observed local trends of element abundances with density are used to constrain the model of dust growth. I will discuss the physical conditions under which most of dust mass grows, time spent by grains in various environments and dust lifetimes inferred from the modelling of dust evolution. I will also present the dust and gas column density maps derived from their final spatial distribution in the numerical simulations.

March 2016

March 25: Holiday

March 18: No talk

March 11: Falling outer rotation curves of star-forming galaxies at 0.7 < z < 2.6 probed with KMOS-3D and SINS/zc-SINF.   - Philipp Lang

The rotation curves of star-forming galaxies at high redshift are currently well probed in their inner parts through deep IFU kinematics, while their extended shapes reaching to the outer faint levels of the disk are still largely unconstrained. I will present the results of a project  examining the unexplored outer rotation curves of star-forming galaxies at high redshift, exploiting the deep H-alpha IFU kinematic data from the  SINS/zc-SINF and KMOS-3D surveys. Through stacking the signal of ~100 massive galaxies at 0.7 < z < 2.6, a representative rotation curve out to  several effective radii can be constrained. The stacked rotation curve exhibits a turnover with a significant decrease in rotation velocity in  the outer regions, significantly strengthening the tantalizing evidence previously hinted at in a handful only of individual disks among the sample with the deepest data. These results are in good agreement with recent studies demonstrating that star-forming disks at high redshift are strongly baryon-dominated; the steep falloff of the outer rotation curve further indicates a significant level of pressure support at large radii, with important implications on the outer disk structure of massive
high-redshift galaxies. 

March 4: Where is the torus? - Leonard Burtscher

Mid-IR interferometry at the VLTI has resolved parsec-scale dusty structures in about 30 AGNs by now. We know they are composed of two distinct components and in a few well-resolved cases the dominant component is seen to be elongated in the direction of the narrow-line region -- quite in contrast to what is expected for the torus of the unified scheme. In a recent study ( we systematically constrained the detectability and prevalence of elongations in the entire sample. Is polar elongated mid-IR emission the end of the simple torus picture?

February 2016

February 26:  ISM day (MPA)

February 19: No talk

February 12: SPIFFI upgrade - Liz George and Dominik Gräff 

In January our group upgraded the VLT-Instrument SPIFFI, which is part of SINFONI. We want to deliver you an insight into this upgrade by talking about our work on Paranal - about the things we wanted to change in SPIFFI and the things we actually changed; about problems that occurred while the upgrade and how we solved them; and finally about commissioning and the new performance of SPIFFI. 

February 5: ALMA reveals rapid formation of a dense core for massive galaxies at z~2 - Ken-ichi Tadaki

At z~2, massive quiescent galaxies are extremely compact with a dense core while the majority of star-forming galaxies have more extended stellar disks. Here, a simple question is how the dense core is formed. I will present high-resolution (0.16"~1.3kpc) ALMA observations at 870 um for 25 massive galaxies on the star formation main sequence at z~2, and compare the  spatial distribution of the rest-frame far-infrared emission with stellar mass maps derived from spatially resolved stellar population modeling. The high-resolution ALMA data reveal that the dust continuum emission is mostly radiated from single region close to the galaxy center and its half light radius is more compact by a factor of 2-3 than the rest-frame optical light and stellar component. The extremely compact starburst can build up a dense core within a few hundred Myr. We may be witnessing an evolutionary pathway from extended star-forming disks to compact galaxies.

January 2016

January 29: Broad [CII] and CO(1-0) line wings as tracers of molecular outflows - Annemieke Janssen

We study a sample of 22 local (z < 0.1) ULIRGs, of which 16 are known to have molecular outflows as traced by blue-shifted OH absorption (at 119 um). Most objects in the sample also have broad [CII] wings, and for these objects the FWHM of the [CII] component correlates well with the blue-shifted OH velocity. Moreover, the outflow masses derived from [CII] and OH 119 are similar. This means that one might use [CII] broad wings as a tracer of molecular outflows. We furthermore want to know whether there is an equally good correlation with CO(1-0). I will present the ALMA data we got on 4 objects in the sample, and discuss some difficulties with the data reduction / interpretation. 

January 22: Practical MCMC - Philipp Plewa

I will start by briefly introducing the basic principles of parameter estimation and model selection from a Bayesian perspective. Then I will explain step by step how to use two popular implementations of different MCMC algorithms (emcee and MultiNest) to solve one particular example problem.

January 15: Molecular Cloud Structure and the Star Formation Process at Low Metallicity - Andreas Schruba

Stars from in cold, dense clouds of molecular gas. However, our understanding of the physical processes that control molecular cloud and star formation remains limited, especially at low metallicity. I will present ALMA CO observations of the 1/5-solar metallicity Local Group dwarf galaxy NGC 6822 that resolve four star-forming complexes at 2 parsec resolution -- unprecedented for extragalactic observations. The CO-bright clumps are small and have a low filling factor across the galaxy but share similar properties as Galactic clouds of equal size except of somewhat lower CO surface brightness. These CO clumps exist inside larger atomic-molecular complexes with masses similar to Galactic giant molecular clouds. Using dust to trace H2, we infer CO-to-H2 conversion factors ~3 times Galactic but with strong variations tracking the region's evolutionary state. The SFR-to-H2 ratio of these regions is quite high (~1/100Myr) but models of cloud evolution suggest that this measurement is biased by our focus on visible star-forming regions and may be in agreement with typical global star formation efficiencies of ~1/0.5Gyr also found for other dwarf galaxies.

January 8: The first rotation curve for a quiescent galaxy at high redshift - Sirio Belli

While surveys like KMOS-3D are finally measuring the rotation for hundreds of gas-rich galaxies at high redshift, the kinematics of gas-poor quiescent galaxies are still largely unknown, because of the intrinsic difficulty in measuring spatially-resolved absorption lines. One way to obtain the required high signal-to-noise ratio and spatial resolution is by taking advantage of strong gravitational lensing. However, most lensed galaxies are star-forming, and it is extremely rare to find high-redshift quiescent galaxies that happen to be strongly lensed. I will present the discovery and observation of one such rare system: a massive quiescent galaxy at z=2.6 that is multiply imaged by a foreground cluster. We obtained near-infrared spectra using Keck and Magellan, and we measured a significant amount of rotation. This is the first such measurement at z>1, and has important implications for models of galaxy quenching and evolution.

December 2015

December 18: Proper motions outside of the Galactic Center - Tobias Fritz, University of Virginia

December 11: IR RETREAT

December 4: Spectral study of S-stars in the Galactic center - Maryam Habibi

The presence of young massive stars in the vicinity of the supermassive black hole, Sgr A*, is puzzling given how inhospitable the region is for star formation. I present the result of 11 years (2004-2015) of high resolution spectroscopy within the central arc second of the Galactic center. By coadding the 50-100 hours of spectra we have obtained high signal/noise (50-400) spectra in H- and K-band for a sample of 8 stars orbiting the central super massive black hole. We use these data to derive improved radial velocities and therefore improved 3d stellar orbits. Our deep spectra combined with model atmospheres can be used to constrain their stellar properties in order to investigate their true nature as massive stars.

November 2015

November 27: The impact of environment on the evolution of protoplanetary discs: external photoevaporation and tidal encounters - Stefano Facchini

There is observational evidence that the environment of star forming regions can significantly affect the evolution of protostellar and protoplanetary discs. On one hand, the energetic radiation permeating young associations can drive photoevaporative winds from the discs' outer regions. On the other hand, gravitational interactions between stars within the cluster are expected to strongly perturb and affect the discs. Firstly, I will show that new hydrodynamical models indicate that the mass loss rates due to photoevaporation are high enough to affect the global evolution of protoplanetary discs, and thus limit their planet formation potential, even in moderate environments. Secondly, I will show recent observations at multiple frequencies of the RW Aur system. This peculiar binary system is very likely undergoing a tidal encounter caused be the secondary star, and it is the best candidate up to date to test well known theoretical models of star-disc interactions. We will see that these interactions not only affect the large scale structure of discs, but can have a significant impact in shaping the properties of their inner regions.

November 20: Tracing H2 in galactic and extragalactic systems using CI as a proxy - Thomas Bisbas

Molecular hydrogen is the most fundamental species in the Universe making up ~70% of its total baryonic non-stellar mass. Owing to
its quantum mechanical properties however, H2 is not readily observable by radiotelescopes and CO has been widely used as its tracer. During the last 5 years there is a growing evidence that the `traditional' CO-to-H2 method may not be accurate or even applicable to extragalactic studies. In this talk we will discuss the utility of CI in tracing H2 in the Universe focusing on the newly discovered effect of CO-destruction due to cosmic rays. CI appears to be a powerful tracer for extragalactic studies and CI-to-H2 methods become popular in the community particularly since ALMA open its eyes. 

November 13: The ionized gas in nearby galaxies as traced by the [NII] 122 and 205 um transitions - Rodrigo Herrera-Camus

The [NII] 122 and 205 um transitions are powerful tracers of the ionized gas in the ISM: (1) the [NII] 122/205 line ratio can be used to measure the electron density of the low-excitation, ionized gas, and (2) the intensity of these lines is directly related to the flux of ionizing photons, probing the most recent star formation activity. The study of these applications in nearby galaxies is specially relevant now that ALMA can observe both [NII] transitions at z>2. In this talk I will present Herschel observations of these pair of [NII] far-infrared lines in 21 nearby galaxies selected from the KINGFISH and Beyond the Peak samples. I will discuss the reliability of the [NII] lines as star formation tracers, and how the electron density of the ionized gas is related to other relevant ISM properties (e.g., radiation field strength, star formation activity, dust temperature, etc).

A more detailed abstract can be found here:

November 6: no talk

October 2015

October 30: Molecular gas in distant cluster galaxies and Eddington-limited star formation in compact mergers. - Gregory Rudnick, University of Kansas

I will present updates on two projects.  
The first project involves extremely deep CO(1-0) observations of molecular gas in star-forming galaxies residing in a z=1.62 proto-cluster.  These galaxies are massive, have high gas fractions, and long gas consumption timescales and they lie off the Genzel+15 scaling relations.  They are also surprisingly compact, which may yield information about the stability of their molecular gas.  I will discuss these results, what role they might play in motivating blind CO surveys, and the implication for the future star formation history of these cluster galaxies.
I will also present results from a project focussing on compact galaxies at z~0.6 that appear in the optical as very blue post-starbursts.  These galaxies are driving very fast winds, with speeds of up to 2000 km/s and, surprisingly, appear to host highly obscured star formation that has sufficient energetics to drive large multi-phase outflows without the need for an AGN.  This star formation is nearly at the galaxy-wide Eddington-limited for star formation and may indicate the final blowout of these galaxies.  I will discuss the characteristics of this enigmatic population and our current efforts to understand them.

October 23: The FIR emitting region in local galaxies and QSOs: Size and scaling relations - Dieter Lutz

October 16: First Results From the IGRINS Infrared Spectrograph - Daniel Jaffe (University of Texas) and Casey Deen (MPIA)

IGRINS, the Immersion Grating Infrared Spectrograph has a resolving power of 40,000 and covers the entire H and K bands, 1.4-2.5 microns in a single exposure.
The instrument has no moving parts.  It has just completed its first year of observations on the McDonald Observatory 2.7m telescope. On the 2.7m, it has ~70% of the instantaneous S/N of CRIRES on the VLT while having 30 times the spectral grasp.  We report on some of the outstanding first year results in studies of young stellar objects, stars, and the interstellar medium.

October 9: The ionizing radiation in star-forming galaxies - Lisa Kewley, ANU

October 2: Implications of X-ray population studies for the torus geometry and the SMBH accretion history - Johannes Buchner, PUC, Chile

In my PhD at the high-energy group in MPE I have spent much effort developing a consistent Bayesian spectral analysis and luminosity function methodology that can robustly constrain AGN demographics while incorporating all sources of uncertainties. I will discuss results from such X-ray studies working on the demography of AGN: their space density, the fraction of obscured and Compton-thick AGN, their evolution with redshift and luminosity.
From the luminosity-dependence of the obscured fraction, and its evolution, we can draw strong conclusions on how the torus is maintained. I also discuss whether the discovered Compton-thick population (38+-7%) is sufficient to explain the locally determined SMBH density.

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