The full 2024 schedule can be found here

May 2025

May 9: The GC in 2025: predictions, progress and prospects. -- Diogo Ribeiro

From parsec to event-horizon scales, the galactic center represents our best laboratory to study what happens in some of the densest star systems in the universe. Every year, observations yield data that deepens our understanding of this region of our galaxy. 2025 is no exception. With new observations happening this weekend, it is the perfect excuse to breakdown what the galactic center may tell us this year. In this week's tea talk, I'll go over some of the past GRAVITY results in the GC, where they've led us and where we are headed. 

April 2025

April 25: Decoding Gravitational Waves with Dual (and Binary) AGN -- Martina Scalpi

A large population of AGN pairs residing within the same galaxy — the  so-called dual AGN — is predicted to exist at redshifts z > 0.5.  These systems represent the parent population of merging black holes  (BHs), making their number and properties a crucial starting point for  theoretical predictions of the gravitational wave (GW) background and  event rates explored by pulsar timing array (PTA) experiments and, in  the future, by the LISA mission.
Until recently, only a handful of dual AGN had been identified at  sub-arcsecond separations. In this talk, I will present the first  statistically significant sample of such systems, with projected  separations ranging from 0.15″ to 0.8″ — corresponding to kiloparsec  scales at z > 0.5 — selected using the innovative Gaia Multi-Peak  (GMP) technique.* *However, follow-up observations are  essential to confirm the nature of these sources and to distinguish  genuine dual AGN from gravitationally lensed systems. I will showcase  spatially resolved optical and near-infrared spectroscopy of ~50 systems at cosmic noon, and present an analysis of their key physical  properties — including luminosity and mass functions, separation  distributions, their fraction within the overall AGN population, and how these properties evolve with redshift.
Finally, I will briefly discuss the role of GRAVITY in the search for binary AGN, merging AGN at parsec-scale separations.

April 11: An Update on the z=2 GRAVITY+ Quasar Programme -- Taro Shimizu

April 4: Overview of the GRAVITY+ commissioning: from Germany to Chile, and expanding horizons. -- Guillaume Bourdarot

GRAVITY+ aims to improve by orders of magnitude the performances of GRAVITY and VLTI, for which a key step is the development of a high-order and laser guide star Adaptive Optics (AO) system. In this talk, I will present an overview of the Gravity Plus Adaptive Optics (GPAO) integration and commissioning, which took place from July 2024 until December 2024 in Paranal, Chile. This includes the instrumentation work done by many of our IR group members, the integration and deployment of the system in Paranal and its first-light. These observations include the first spatially resolved observations of a BLR at redshift z~4, spectroscopy of exoplanets and cool brown-dwarf down to a magnitude 21.0 in the K-band, and the first resolved observations of the inner astronomical unit of HL Tau with GRAVITY. These developments are paving the way for the arrival of the Laser Guide Stars in Fall 2025, and are already opening up the parameter space covered by infrared interferometry and future instrumentation.

March 2025

March 28: Spirals & Bars in cosmic noon disks -- Stavros Pastras

March 14: Probing galaxy properties and evolution through multi-wavelength spatially resolved studies -- Letizia Scaloni

March 7: Galaxy Morphologies at Cosmic Noon with JWST: A Foundation for Studying Rapid Inflows and their Connection to Bars and Spiral Arms -- Juan Espejo

Recent studies led by the IR group have identified rapid inflows in star-forming galaxies, raising fundamental questions about how these processes influence galaxy evolution at cosmic noon and the emergence of well-ordered structures seen in the local Universe. These findings align with our evolving understanding of galaxy morphologies over the past few decades. Since the 1990s, observations have reshaped our perception of galaxy structure, revealing that systems once thought to be clumpy and chaotic are in fact ordered disks, some of which exhibit complex internal features such as spiral arms and bars. Advances in kinematic studies, HST imaging, and, more recently, JWST have enabled more precise morphological classifications, allowing us to identify galaxies with intricate structures—including bars and spiral arms—previously obscured by dust. These features are key targets for studying rapid inflows, non-circular motions, and disk instabilities. We investigate the morphology of massive star-forming galaxies at 0.8<z<1.3 and 2.0<z<2.5, epochs marking the peak and decline of cosmic star formation, both well-covered by kinematic surveys. Using JWST/NIRCam imaging, we visually classify 1,451 galaxies, count spiral arms, analyze non-parametric morphological indicators and study their relation with the dynamical support as measured via v/σ. Disk galaxies dominate the sample (82%), with 40% of them exhibiting spiral structures and 11% containing bars. We find that the prevalence of two- and three-armed spirals remains largely unchanged across redshifts and that non-parametric indicators correlate with stellar mass but show no significant evolution with redshift. From the kinematic analysis, we find that disk morphology is strongly associated with high rotational support, with the majority of disks exhibiting v/σ>3. This study establishes a robust population-wide framework for linking galaxy morphology and dynamics at cosmic noon, providing a key reference for future studies on the role of detailed morphological features in galaxy evolution.

February 2025

February 28: Finding faint stars in the Galactic Center with GRAVITY -- Felix Mang

GRAVITY has opened us the door to measure effects of General Relativity on the star S2 in the Galactic Center. These effects are only sensitive to the high mass/strong gravitational field of SgrA*. Besides mass, a black hole is also characterized by its spin or angular momentum according to the 'No-hair' theorem. The S-stars in the GC are in principle also affected by it, but deviations from Kepler orbits steeply drop off with distance to the dominating mass. Within currently accessible magnitudes, no star has been found orbiting SgrA* close enough to be sensitive to its spin. The quest is hence to push for fainter magnitudes and potentially find faint yet undiscovered stars in the GC.

In my talk I will present a comprehensive summary of my first project as PhD student, dedicated to improving the image reconstruction method GRAVITY-RESOLVE (G^R). G^R is an imaging tool specifically designed for GC observations with GRAVITY, aiming to reconstruct point sources within 100 x 100 mas around SgrA*. The revision of the entire model and inference yielded a reduced runtime of a few percent and resulted in better convergence for robust and deeper imaging. The drastic reduction in runtime enables us to apply this method during GC observations, acting as an 'imaging pipeline'.

Besides the development of this method, focusing on astrophysics, I will showcase its application to GRAVITY data and present a number of results. I will give an update on the orbit of S301, a faint star detected in 2023, and point out implications of its potentially tight orbit on relativistic effects. Moreover, I will display a movie of the GC, consisting of individual reconstructions of every GRAVITY dataset in 2021 - 2024, vividly illustrating the motion of S-stars within 200 x 200 mas. Finally, I will show the trajectory of S62 over the course of four years, which potentially undergoes a gravitational lensing event this year.

January 2025

January 24: Protostars and young disks with JWST -- Ewine van Dishoeck

Understanding how stars and planets are built requires observations at long wavelengths in order to penetrate their dusty natal clouds.  Webb is orders of magnitude more sensitive than previous missions and has subarcsec resolution in the infrared.  Webb is therefore eminently suited to study the physical and chemical structure of embedded protostars and disks. A single data set can address many different science questions, each of which will be discussed in this talk. Jets, winds and outflows are beautifully imaged in various atomic and H2 lines, and can be used to determine mass loss rates and address the question to what extent grains are destroyed in jets.

Rich ice spectra are seen in the cold outer envelopes of protostars providing evidence for the presence of simple and, for the first time,
complex molecules in ices.  Ammonium salts are also seen abundantly and turn out to be a significant reservoir of the missing sulfur. In
addition, gaseous molecules such as CO, CO2, H2O, and SO2 are seen in the mid-infrared spectra, including NH3 for the first time. These
lines can be used to probe the composition of hot cores and compare gas phase abundances with those in ices to assess the importance of ice sublimation versus high temperature chemistry.

A final topic concerns the structure of young disks in the embedded stage. So far, these young disks are found to be surprisingly poor in
lines. This is in contrast with more mature disks around T Tauri stars observed in the MINDS program, whose rich spectra show many lines from gaseous molecules including surprising new hydrocarbon molecules. See miri.strw.leidenuniv.nl for more details.

January 10: A Joint ALMA and JWST View of z>4 Galaxies -- Eleonora Parlanti

Before the launch of JWST, ALMA was the ideal instrument for studying the properties of galaxies at z > 4 through far-infrared emission lines. With the advent of JWST, we can now complement ALMA observations by accessing, for the first time, the rest-frame optical emission of high-redshift galaxies. This synergy provides a more complete view of the multiphase gas and feedback processes in high-z galaxies, unveiling their physical properties, gas kinematics, and the interplay between cold and ionized gas.

December 2024

December 13: Spectroscopic AGN Survey at z ∼ 2 with NTT/SOFI for GRAVITY+ Observations -- Daryl Santos

With the advent of GRAVITY+, the upgrade to the beam combiner GRAVITY at the Very Large Telescope Interferometer, fainter and higher redshift active galactic nuclei (AGNs) are becoming observable, opening an unprecedented opportunity to further our understanding of the cosmic coevolution of supermassive black holes and their host galaxies. To identify an initial sample of high- redshift type 1 AGNs that can be observed with GRAVITY+, we have obtained spectroscopic data with NTT/SOFI of the most promising candidates. Our goal is to measure their broad line region (BLR) fluxes and assess their physical geometries by analysing the spectral profiles of their Balmer lines. We present 29 z ∼ 2 targets with strong Hα emission in the K-band. Their line profiles are strongly non-Gaussian, with a narrow core and broad wings. This can be explained as a combination of rotation and turbulence contributing to the total profile or two physically distinct inner and outer regions. We find small Hα virial factors, which we attribute to the low FWHM/σ ratios of their non-Gaussian profiles, noting that this can lead to discrepancies in black hole masses derived from scaling relations. We also find two targets that show tentative evidence of BLRs dominated by radial motions. Lastly, we estimate the expected differential phase signals that will be seen with GRAVITY+, which will provide guidance for the observing strategy that will be adopted.

November 2024

November 29: IT @ MPE: Services, Tools, Best Practices, Recommendations -- Alex Agudo

Where do you find what you are searching for?

How do you know what you are searching for?
Why are you searching at all, rather than having it searched for you?
Introduction to services and tools available at MPE and related institutions along with recommendations, best practices etc.

November 15: Shoulder-to-shoulder: ALMA and JWST get together to understand the formation of planets.-- Nicolas Kurtovic

Exoplanets are a common outcome of the star-formation process. Some of the most relevant properties of planetary systems are set during their formation: the number of planets, mass, architecture, and composition. In this talk, I will focus on what we have learned about planet formation on the most common type of stars: late M-dwarfs and binaries, and how the combination of ALMA with JWST/MIRI gives us a full picture of the planet-formation environment.

October 2024

October 25: Hello again -- Hannah Übler

I will give an overview of my work with the NIRSpec GTO team during my post-/pre-MPE time, and a preview on ongoing and planned projects during the next years.

October 18: Exploring the magnetised early Universe -- Jinahang Cheng

Magnetic fields permeate almost all astronomical scales, from planetary disks to the stars, from black holes to galaxies. They are integral to processes such as the origin of life, star formation, and black hole activity. However, the influence of magnetic fields on galaxies remains a topic of debate, largely due to limited observations, especially in early galaxies. This talk will focus on a novel approach to map galactic magnetic fields in distant galaxies using polarised dust emission. By integrating observations of magnetic field structures with galaxy kinematics, I will also discuss their origins and how these observations shed light on their influences on galaxy evolution.

September 2024

September 27:   Rotation curves at large radii inferred from stacking KMOS3D galaxies -- Jean-Baptiste Jolly

The shape of rotation curves has long been one of the main direct method to infer dark matter fraction of galaxies. With the advent of new telescopes and instruments the study of rotation curves has become increasingly possible at higher and higher redshift. However, due to data quality and signal-to-noise ratio constraints such analyses are typically limited to the inner part of galaxies --where the kinematics are more dominated by the baryons-- or to size-limited sample. 

In this talk I will present a novel stacking method allowing us to extend rotation curves studies up to larger radii (5 Re) in statistically sound samples, using a genetic algorithm coupled to agnostic spectral stacking. I will detail the functioning of the algorithm, its test on mock data and its first application to the KMOS3D survey

September 20:  The extended mass distribution in the Galactic Center -- Matteo Sadun Bordoni

Since 2016, the GRAVITY interferometer at ESO's Very Large Telescope has enabled us to obtain astrometric data with unprecedented accuracy for the S-stars orbiting Sagittarius A*, providing a powerful means to probe the gravitational potential surrounding the supermassive black hole at the center of our Galaxy. In particular, we have successfully detected the in-plane, prograde Schwarzschild precession of the orbit of the star S2 and the gravitational redshift of its spectral lines, as predicted by General Relativity.

In this presentation, I will explore the implications of an extended mass distribution around Sagittarius A*, which is expected to primarily consist of a dynamically relaxed cusp of old stars and stellar remnants, along with the potential presence of a dark matter spike. Assuming the distribution follows a smooth, spherically symmetric density profile, it would add a retrograde precession of the stellar orbits, counteracting the prograde relativistic precession. By analyzing S-stars data, we establish stringent upper limits on the enclosed mass within S2’s orbit — approximately 1200 solar masses within the central 10 milliparsecs of our Galaxy — assuming plausible density profiles. We compare this observational constraint with theoretical expectations for a dynamically relaxed stellar cusp in the Galactic Center, finding that our upper limit closely aligns with the predicted value from numerical simulations, leaving little room for a significant enhancement of dark matter density near Sagittarius A*. 

Additionally, the simulations predict that, due to mass segregation, stellar mass black holes dominate the mass distribution at these radii, indicating that the mass distribution within S2’s orbit is not smooth but rather consists of a finite number of bodies. This granularity of the mass distribution can lead to significant deviations in the orbital motion of stars compared to a smooth distribution, disrupting spherical symmetry and leading to scattering events. Through numerical simulations, I aim to investigate whether these deviations could be observable in the orbit of S2, given the current astrometric accuracy of GRAVITY, and whether they might perturb our measurement of the Schwarzschild precession of its orbit.

September 13:  My Journey to the West -- Jinyi Shangguan

After six years as a postdoc at MPE IR group, my journey has been full of excellent experiences. In this talk, I will share memorable moments and highlights from both my personal and research life. I'll also discuss exciting future prospects, including projects involving GRAVITY+, and great opportunities of collaboration between MPE and Peking University (that I will move to).

September 6:   Quantitative morphology as part of the JWST morphology project -- All hands + Josef Vacha

I will be presenting my work on the JWST morphology project, which came about through an internship I've undertaken in the Galev group over the past 6 weeks. In this work, I’ve expanded on previous visual classifications by calculating various quantitative morphological indicators, such as CAS, Gini-M20, and other statistics derived from JWST galaxy images. I will explore how these indicators reflect galaxy morphology evolution as a function of redshift and mass and discuss their consistency with visual classifications and previous studies using HST data.

August 2024

Summer break

July 2024

July  26:  [C II] spectral imaging of the Galaxy's Central Molecular Zone -- Andy Harris

Culminating years of evolution by related groups, a major SOFIA-upGREAT project has provided a data cube that covers the Galaxy's Central Molecular Zone.  These data provide a high-resolution view of not only our own Galactic center, but serve as guides to interpreting far-infrared fine structure emission from other galactic nuclei.  The fully-sampled and velocity-resolved [C II] data, covering Sgr A, B, and C, have 0.55 pc spatial and 1 km/s velocity resolutions, revealing connections between and separating different physical components along the line of sight. I'll provide a brief summary of some of the major highlights we found across the region.

July  19:  The star formation efficiency and physical conditions of the ISM in galaxies from the local and early Universe -- Vicente Villanueva

We study galaxy samples representative of the local (EDGE and VERTICO surveys) and early universe (CRISTAL survey), combining interferometric CO, [CII], dust-continuum data and IFU optical spectroscopy. We focus on the radial dependence of the star formation (SF) efficiency of the total gas on morphological, structural, and dynamical properties of the galaxies. We test the impact of environmental processes on galaxies from the Virgo cluster. Our results show that the cluster environment not only affects the outskirts of galaxy disks and their atomic gas, but deeply changes the distribution and efficiency of the centrally located molecular gas component. We study the onset of SF quenching by investigating a sample which encompasses main sequence (MS), green valley (GV), and red cloud (RD) galaxies. We note that GV galaxies have lower molecular SF efficiencies than galaxies on the MS, particularly within galaxy centers. We also present new [CII] 158 um and dust continuum observations of HZ10, a dusty MS galaxy system at z=5.66. Our results suggest that the UV emission (likely from young stellar populations) is strongly affected by dust attenuation in the more dusty components of the HZ10 system.

July  12:  Building multiwavelength databases for nearby galaxy surveys  -- Yixian Cao

Mutliwavelength mapping surveys of nearby galaxies provide a wealth of data for studies on galaxy evolution. Databases constructed based on these surveys are not only useful in facilitating scientific studies, but also beneficial in effectively managing the data. In this short presentation, I will discuss the design, implementation, and usage of such databases, focusing on instances from EDGE and PHANGS surveys.

July  5:  All Hands Meeting

June 2024

June 21:  New evidence for an intermediate-mass black hole in ω Centauri --  Maximilian Häberle

June 14: The Black Hol(e)der: Understanding gravity with SgrA* --  Diogo Ribeiro

Sagittarius A* is the prime example of the existence of black holes. Precise stellar astrometry and spectroscopy have been used to observe both the gravitational redshift signature in the orbit of the star S2 and the prograde relativistic precession predicted by the Schwarzchild solution. Deeper in the gravitational potential, electromagnetic emission from a distance of a few gravitational radii has been detected at several wavelengths and resolved temporally and spatially in the Near Infrared. The feasibility of such studies makes SgrA* and its surroundings the best laboratory for studying gravity in the strong field regime. In this talk, I'll explain why and how we precisely track the motion of stars and gas around SgrA* and discuss the current joint theoretical and observational efforts employed by the GRAVITY collaboration to understand gravity ever closer to SgrA*.

June 7:  Fast and precise image reconstruction of the Galactic Center with GRAVITY(+) --  Felix Mang

May 2024

May 23: Arrayed waveguide grating (AWG) based photonic spectrograph for the astronomical J band  --  Vishaal Gopinath

The use of adaptive optics to realize (close-to) diffraction-limited telescopes in the infrared enables the use of single-mode photonic devices, which work independent of the telescope diameter. This can dramatically reduce costs mass, and volume constraints. A possible single-mode counterpart to conventional spectrographs with bulk optics are photonic spectrographs on arrayed waveguide grating (AWG). We developed an AWG for the astronomical J band (center wavelength 1250 nm). The device has been fabricated and was characterized using a test bench built in-house at ESO. The AWG was found to display spectral resolutions close to the design resolution R ~12000, over a much larger working range than expected. Our results demonstrate the possibility and potential to use AWG in astronomical spectrographs in future instruments. 

May 3:  Ground-based Optical/IR Research Infrastructures in the Coming Decade --  Ric Davies

April 2024

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 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

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.

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

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.

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
 

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 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 G^R - 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 (G^R) 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 G^R, 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 G^R, 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 G^R 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 (www.alma-cristal.info), 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

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 Θ_BLR (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 M_BH/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

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

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. (https://arxiv.org/abs/1803.08925) 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 (https://github.com/pmplewa/GCGAN) 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 (http://doi.org/10.1093/mnras/sty512), efficient photometric stellar classification (http://doi.org/10.1093/mnras/sty511), and the correction of image distortion (http://doi.org/10.3847/2515-5172/aab3df).

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.