Research of the Infrared/Submillimeter Group at MPE

Research of the Infrared and Submillimeter Group is focused on the fields of evolution of galaxies and galactic nuclei, including the center of our own Galaxy and starburst phenomena as well as studies of the dense interstellar medium in star- and planet-forming regions. See this link for a list of highly cited IR group papers, with at least 100 citations.


The Galactic Center

(See also dedicated Galactic Center page)

Our own Galactic Center is a unique astrophysical laboratory for studying black holes. It provides the best evidence for the existence of massive black holes in galactic nuclei. Due to its relative proximity, we can study the stellar dynamics in the central parsec around the massive black hole by tracking individual stellar orbits, the composition of the stellar population, and the flaring emission from the immediate vicinity of the massive black hole in unprecedented detail.

To this end, we have employed diffraction-limited infrared imaging and spectroscopy, using ESO’s NTT from 1992 to 2002, followed by the adaptive-optics instruments NACO and SINFONI mounted at ESO’s VLT from 2002/2004 to 2019. These two instruments have been replaced by ERIS with a high-order adaptive optics system, which we use since 2022. Our team has built GRAVITY, an interferometer that can simultaneously combine the light of the four 8m telescopes of the VLT. We use GRAVITY since 2017, reaching a resolution of around 3 milliarcseconds in the astronomical K-band, and an astrometric accuracy of 30 microarcseconds. This was the key to detect relativistic effects in the motions of the stars around the massive black hole.

Our work has received the highest possible recognition with the award of the 2020 physics Nobel prize to Reinhard Genzel.


Key publications:


Evolution of Galaxies

Dynamics and Evolution of High-Redshift Galaxies
(See also dedicated Galaxy Evolution page)

Observations of distant galaxies are essential to determine the physical processes that drive their growth and evolution over cosmic time. Spatially and spectrally resolved data of rest-frame optical line emission are a powerful tool to characterize these processes.  By using integral field spectroscopy with SINFONI, KMOS, and ERIS at the VLT, we investigate the dynamics, structure, star formation, gas excitation and metallicity, and outflows of representative samples of z ~ 0.5–3 galaxies, spanning six billion years around the peak epoch of cosmic star formation activity.


Review articles:


Key publications:

 

The Role of Molecular Gas in Galaxy Evolution
(See also dedicated PHIBBS page)

Continuing technological progress, in particular at the IRAM Plateau de Bure with the NOEMA interferometer, enables us to study the cosmic evolution of the galactic molecular gas reservoirs as well as to map its distribution and kinematics within galaxies. Our observational programs have greatly advanced the characterization of the cold gas content across the massive star-forming galaxy population at z ~ 0.4–3.  With the higher sensitivity and angular resolution afforded by NOEMA's most recent upgrades, our observations are revealing more directly the importance of disk and bulge buildup via gravitational instabilities and gas transport.


Key publications:

 

The Nature of High-Redshift Infrared Sources
(See also PEP page)

Surveys at mid-infrared and (sub-)millimeter wavelengths with ISO, SCUBA, MAMBO, Spitzer, and Herschel have uncovered populations of massively star-forming galaxies at high redshift that constitute a major part of the total cosmic star-forming activity and a key phase in the evolution of massive galaxies. We are studying the nature of these objects in the context of the evolution of massive galaxies.


Key publications:

 

The Structure of AGN

 

(See also AGN Page)

Our tools like high-spatial-resolution near-infrared spectroscopy, near-infrared and millimeter interferometry, and mid-infrared spectroscopy are ideal for addressing questions on active galactic nuclei and their environment. Among others, projects have dealt with the characterization of circumnuclear starbursts, the distribution and dynamics of circumnuclear gas, and the properties of the obscuring material. Recent work has focused on spatially resolving the BLR and hot dust on subparsec scales through a large program with GRAVITY.


Key publications:

 

Ultraluminous Infrared Galaxies and QSOs

(See also SHINING Page)

UltraLuminous InfraRed Galaxies (ULIRGs) play a key role in scenarios for the formation of Quasars and of elliptical galaxies, and serve as possible local analogues to high-redshift sources above the star-forming sequence. We have tested the energy sources of ULIRGs and QSOs using ISO, Spitzer, and Herschel mid- and far-infrared spectroscopy and near-infrared imaging spectroscopy.


Key publications:


      Studies of Star and Planet Formation and the Dense Interstellar Medium

      Structure and Evolution of Protoplanetary Disks

      Young pre-main sequence stars are surrounded by rotating disks of gas and dust out of which planets can form. We are carrying out a number of combined observations and modeling projects to understand their physical and chemical structure by using submillimeter data from ALMA, complemented by infrared spectroscopy with VLT-CRIRES+, VLTI-GRAVITY, Herschel, and now JWST-MIRI (MINDS program). ALMA allows us to resolve the chemistry, gas and dust structures in detail in both radial and vertical direction. Infrared spectroscopy probes gas in the inner region (<few au) where terrestrial planets form. JWST is revealing a large diversity in inner disk chemistry, with some disks being rich in gaseous H2O perhaps linked to transport processes from the outer disk. Disks around very low-mass stars (<0.3 MSun) are surprisingly rich in hydrocarbon molecules. Taken together, these studies set the scene for connecting the chemistry of disks with that of exoplanet atmospheres and providing clues on what sets their composition.


      Key publications:

       

      Water and Organic Molecules in Star-Forming Regions

      Water is one of the most abundant and important molecules in star- and planet-forming regions: it acts as a major reservoir of oxygen, as a gas coolant, and (as ice) assists planet formation. Both water and complex organic molecules are directly associated with the biology of living organisms on Earth. We are using ALMA, NOEMA, Herschel, VLT, and now JWST-MIRI to observe water (including its deuterated form) and organic molecules in both ice and gas toward a large sample of protostars. These include a wide range of masses and luminosities, from the lowest- to the highest-mass protostars, and a great variety of evolutionary stages, from the first stages of clouds prior to collapse to the last stages represented by pre-main sequence stars surrounded by disks. A suite of molecular excitation and radiative transfer tools has been developed, and many ice spectra have been measured in the Leiden laboratory. Together, the data show that water and complex molecules are formed early as ices on the surfaces of grains in cold clouds and are largely preserved in their journey from dense clouds to disks.


      Key publications:


      Studying the ISM and Gas-Star Cycle in Galaxies at Molecular Cloud Scale

      To grasp the growth and evolution of galaxies requires an understanding of the physics that regulate the gas-star cycle within galaxies. We are carrying out state-of-the-art hydrodynamical simulations of the physical, chemical, and dynamical properties of the multi-phase ISM driven by supernovae in star-forming galaxies, especially at high redshift, at a range of scales and in different environments down to low metallicities. The simulations can be compared with several legacy-type surveys, carried out by the infrared group using ALMA, NOEMA, VLT, VLA, and HST, and ranging from kiloparsec scales down to a few parsecs. Such studies are important for relating the detailed but small-scale studies inside our Milky Way to the full but poorly resolved galaxy population in the (local) universe and for determining how galactic properties and galaxy evolution are regulated by the small-scale process of star formation and vice versa.


      Key publications:

       

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