Vorträge, Seminare, Ereignisse

Abstract
Where do stars form and how is their formation regulated across galactic disks are two critical questions for our understanding of the star formation process. High angular observations of nearby galaxies allow us to sample the star formation process across galactic disks reaching now regularly the scales of the star-forming units, namely Giant Molecular Clouds (GMCs) and HII regions. Such data provide new insights on the molecular gas reservoir and its role in the star formation process as well as information on the importance of galactic components such as bulges, stellar bars, spiral arms and active galactic nuclei (AGN) in the conversion of cold (molecular) gas into stars. I will introduce the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) survey and present highlights from the collaboration research. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09

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Stellar astrophysics is undergoing a renaissance driven by new observational and theoretical capabilities. Wide-field time-domain surveys have uncovered new classes of stellar explosions, helping to understand how stars evolve and end their lives. Gravitational-wave astronomy is providing exciting insights into the properties of the final remnants of massive stars. Asteroseismology, the study of waves in stars, is also producing dramatic breakthroughs in stellar structure and evolution. Thanks to space astrometry, accurate distances are now available for an unprecedented number of galactic stars. From a theoretical standpoint, it is increasingly possible to study aspects of the three-dimensional structure of stars using targeted numerical simulations. These studies can then be used to develop more accurate models of these physics in one-dimensional stellar evolution codes. I will review some of the most important results in stellar physics of the last few years, and highlight what are the most relevant puzzles that still need to be solved. I will put particular emphasis on the physics of massive stars, which are the progenitors of core-collapse supernovae, gamma-ray bursts and the massive compact remnants observed by LIGO. Dr Cantiello will be based at the Heidelberg Institut fuer Theoretische Studien for his visit to Heidelberg and will be available for meetings by arrangement with his hosts, Fabian Schneider (fabian.schneider@h-its.org), Friedrich Roepke (friedrich.roepke@h-its.org) and Saskia Hekker (saskia.hekker@h-its.org). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09

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Classical Wolf Rayet (WR) stars are hydrogen-free, late evolutionary stages of massive stars. These stars are direct supernova progenitors and undergo intense mass loss. As such, understanding dense and fast outflows of WR stars is crucial for understanding advanced stages of stellar evolution, the dynamical feedback of massive stars on their environments and the characterisation of the distribution of black hole masses. Given the complex optically thick, non-LTE environment, current insights on on WR outflows are usually made with a spherical 1D calculations. However, we know from observations and theoretical simulations that the winds of WR stars are clumped and thus non-spherical effects likely playing an important role to understand them. In my previous and current work, we are developing the first time-dependent, multi- dimensional, radiation-hydrodynamical models of the extended, optically thick atmospheres and winds of the classical WR stars. To make this feasible, we employed a hybrid opacity model using a combination of tabulated Rosseland mean opacities and enhanced line opacities expected within a supersonic flow, resulting in highly structured, turbulent flows. Performing radiative transfer calculations on the resulting hydrodynamic structure, we characterise some of the first conclusions for the observations of WR stars following from these 3D models.

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Every day about five papers are published using Gaia Data Release 2 or Early Data Release 3. Gaia Data Release 3, published on June 13, 2022, will be another source of high-precision data for the astronomical research. The number of stars with 6D phase space information (astrometry plus radial velocities) for stellar dynamical investigations has increased by almost a factor of five, and for the first time more than 100 million low-resolution Bp and Rp spectra become available, providing more detailed information compared to the previous broad-band photometry. Additionally, Gaia DR3 contains special catalogues for multiple stars systems, variable star, and asteroids. Nine performance verification papers, provided by the Gaia DPAC team, demonstrate how to efficiently use the new Gaia catalogue in many different areas of astrophysical research.

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Classical Wolf Rayet (WR) stars are hydrogen-free, late evolutionary stages of massive stars. These stars are direct supernova progenitors and undergo intense mass loss. As such, understanding dense and fast outflows of WR stars is crucial for understanding advanced stages of stellar evolution, the dynamical feedback of massive stars on their environments and the characterisation of the distribution of black hole masses. Given the complex optically thick, non-LTE environment, current insights on on WR outflows are usually made with a spherical 1D calculations. However, we know from observations and theoretical simulations that the winds of WR stars are clumped and thus non-spherical effects likely playing an important role to understand them. In my previous and current work, we are developing the first time-dependent, multi- dimensional, radiation-hydrodynamical models of the extended, optically thick atmospheres and winds of the classical WR stars. To make this feasible, we employed a hybrid opacity model using a combination of tabulated Rosseland mean opacities and enhanced line opacities expected within a supersonic flow, resulting in highly structured, turbulent flows. Performing radiative transfer calculations on the resulting hydrodynamic structure, we characterise some of the first conclusions for the observations of WR stars following from these 3D models.

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Abstract to be arranged. Dr Owen will be based at MPIAstronomie for his visit to Heidelberg and will be available for meetings by arrangement with his host, Laura Kreidberg (kreidberg@mpia.de).

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AGN feedback is now widely considered to be one of the main drivers in regulating the growth of massive galaxies. In my talk I will describe several efforts in our group to understand the power, reach and impact of AGN feedback processes. We find significant evidence for AGN feedback signatures even in low-luminosity AGN and we are now using molecular gas as a tracer to investigate if and how feedback may impact and quench galaxies at low redshift. At higher redshift, it appears that AGN-driven outflows can indeed suppress star formation in their hosts, consistent with the AGN having a ‘negative’ impact on galaxy evolution. However, both star formation and quasar activity peak at z ∼ 2-3 where AGN are expected to impact the build-up of stellar mass the most and I will present recent efforts in our group to characterise feedback processes in powerful AGN on CGM scales at and near Cosmic Noon. In particular, our team recently discovered a unique population of luminous high-z quasars (ERQs) with extreme outflow properties. At the same time, more and more exotic AGN populations with extreme signatures are being discovered at that redshift. These populations are ideal to obtain a census of the overall mass and energy budget of both outflow and infall/feeding from the CGM, an essential requirement to probe the detailed and full feedback loop. Finally, I will also introduce the JWST ERS Program ”Q3D” which will study the impact of three carefully selected luminous quasars on their hosts. Our program will serve as a pathfinder for JWST science investigations in IFU mode. Depending on JWST’s science schedule, I may show some of the very first JWST science images.

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The award winner will present their work.