Seminars and Colloquia at ESO Garching and on the campus

Half of all stars are part of a binary or multiple system, many of which will form together within one circumbinary disc.

The forming stars and disc interact reshaping the disc and the orbits of the binary pair. In this talk, we will look at these effect

with the help of 2D hydrodynamic simulations.We will investigate the impact that the physical conditions in the disc have on

interaction and how the thermodynamics in the disc change the the disc-binary behaviour depending on separation of the binary stars.

This allows us to understand the circumbinary disc structure we can observe with ALMA.

The coupling between the baryonic physics of galaxies and dark matter halo assembly is essential to our understanding of galaxy formation in the standard cosmological model. Yet, it remains elusive to observations given current challenges for measuring halo properties, with studies exploring the galaxy-halo connection typically relying on indirect estimations. In this talk, I will report direct observational evidence indicating that global baryonic properties of nearby galaxies -such as age, metallicity, star formation rate, morphology, stellar angular momentum- are modulated by the mass of their host halos. Thanks to detailed dynamical modeling of high-quality optical integral-field spectroscopic data from the CALIFA survey, we find that all these different galaxy properties depend on total enclosed mass measured up to three effective radii. Notably, galaxies become older, more metal-rich and less rotationally supported, have lower star formation rates and earlier-type morphologies as their total mass decreases (at fixed stellar mass). Furthermore, galaxies with different total masses not only exhibit different global baryonic properties, but also show distinct age and metallicity gradients and radial profiles. We interpret our results as being driven by halo assembly time, with galaxies/halos at different evolutionary stages modulating the variety of galaxy properties observed at fixed stellar mass. All in all, our findings suggest that dark matter halos play a key role in shaping the star formation, chemical enrichment, and assembly histories of galaxies, affecting both their spatially-integrated and -resolved properties observed at present day.

Exoplanets form across a wide range of distances from their host stars, from close-in orbits around the central star to the outer protoplanetary disks.  These environments differ dramatically in physical conditions.  In the inner disk, we use 3D magnetohydrodynamical simulations to study magnetospheric accretion and planetary migration in this highly turbulent region.  We find that Earth-mass planets migrate very slowly, often stalling near the dead-zone inner boundary, while giant planets may halt near the magnetospheric truncation radius.  In the outer disk, beyond tens of au, stellar irradiation — especially when modulated by shadows from the inner disk or accretion columns — can drive a variety of disk structures.  Using 3D radiation-hydrodynamical simulations, we show that these shadows act as an asymmetric driving force, leading to spirals and rings.  They can influence planet formation, and their unique velocity features are potentially observable with ALMA molecular line observations.

We present a study of the instrumental drift in two high-resolution spectrographs for stellar radial velocity measurements. We use a simple model that allows one to calculate the expected drift from measurements of atmospheric temperature, pressure, and humidity. By comparing the real drift with the model predictions, we can identify and possibly correct instrument instabilities produced by effects other than the atmosphere. This method allows us to improve instrument control and enhance the radial velocity performance of spectrographs that do not include simultaneous wavelength calibration. By applying this method, we measure improvements in radial velocity precision from 30 to 15 m/s.

The chemical composition of planets is largely inherited from that of their natal protoplanetary disks. In recent years, the characterization of disk chemistry has advanced significantly. (Sub-)millimeter interferometers such as ALMA have enabled the detection of emission lines from a wide range of molecular species—including deuterated and organic molecules—and revealed their radial and vertical distributions within disks. Meanwhile, JWST has begun to uncover the composition of disk ices.

In this seminar, I will review the chemical evolution of planet-forming disks from the earliest protostellar stages to the emergence of planetary systems, highlighting how accretion and ejection processes, as well as environmental effects, shape their chemistry. I will focus in particular on complex organic and deuterated molecules, which serve as key tracers for reconstructing our chemical heritage through comparisons with the pristine bodies of the Solar System.

Finally, I will discuss how the upcoming SKA Observatory (SKAO) will open new observational frontiers in this field by enabling the detection of emission lines from heavier molecules in planet-forming regions.

Laser propagation through strong turbulence has unique challenges, quite different from astronomical adaptive optics (AO), and therefore unconventional approaches must be developed to meet these requirements. At Fraunhofer IOSB, several wavefront sensing concepts have been either invented or further developed for this purpose. Specifically, focus has always been placed on wavefront sensors (WFS) suitable for monochromatic light, i.e. for lasers, and on achieving the highest possible bandwidth because these sensors' primary application has been deployment on fast-moving aircraft for laser-based communications and energy delivery to/from such aircraft. This presentation will focus on three sensors: the holographic WFS, the heterodyne WFS, and the angular transmission WFS. Application of these WFS to sensing from LGS will be discussed.