Seminars and Colloquia at ESO Garching and on the campus

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.

Mid-infrared polycyclic aromatic hydrocarbon (PAH) features are among the most widely used tracers of star formation in galaxies, as they originate from small dust grains excited by ultraviolet photons from young stars. In active galactic nuclei (AGN), however, the strong radiation field from the central engine can modify or destroy PAH molecules, potentially biasing star-formation rate (SFR) estimates based on these features. Understanding how PAHs behave in AGN environments is therefore crucial to disentangling the nuclear and host contributions to the mid-infrared emission.
In this talk, I will present results from an analysis of low-resolution Spitzer/IRS spectra of 148 nearby AGN (⟨z⟩ = 0.03). We measured the fluxes of the 6.2, 7.7, 8.6, and 11.3 μm PAH bands, derived PAH-based SFRs, and compared them with X-ray properties such as luminosity, obscuration, and Eddington ratio. We find that the 11.3 μm feature is detected in over 90% of our sample and, Its luminosity shows a clear positive correlation with the AGN hard X-ray luminosity, suggesting that star formation and black hole accretion are connected on galactic scales.
Interestingly, this correlation becomes stronger in unobscured systems, consistent with the idea that PAH emission (and therefore star formation) can be affected by the AGN radiation field when the line of sight is relatively clear. No significant trends are found with the Eddington ratio or black hole mass, implying that global star formation is not directly regulated by the instantaneous accretion rate. Altogether, our results show that PAH emission can still be used to trace star formation in galaxies hosting AGN, provided that the effects of AGN luminosity and obscuration are properly taken into account. This work helps us understand how black hole growth and star formation coexist and/or possibly interact.

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.