Seminars and Colloquia at ESO Garching and on the campus

High resolution, hydrodynamic galaxy simulations can be used to investigate the inherent variation of dark matter around the Solar Circle of a Milky Way-type galaxy. These simulations self consistently include both the baryonic back-reaction as well as assembly history of substructures, all of which may have lasting impacts on the dark matter’s spatial and velocity distributions, creating `gusts’ of dark matter wind around the Solar Circle, potentially complicating interpretations of direct detection experiments on Earth. Direct detection is a key experimental goal to advance the microscopic understanding of the dark matter that fills the Universe. We investigate how dark matter substructure, simulated in halos analogous to our own Milky Way, impacts the shape, summary statistics, and interpretation of results from terrestrial dark matter direct detectors.

Implementing a new numerical integration technique, our work generates bespoke predictions for terrestrial underground detection, finding large uncertainties arising in the expected signals of direct detection experiments. Having developed a realistic end-to-end pipeline for studying these effects, we discuss the implications of these astrophysical variations in the dark matter distribution of the solar neighbourhood on current and future particle physics searches for dark matter.

Driven by gravity, galaxies continuously grow through accretion of smaller systems. Stellar streams are nice illustrations of this hierarchical build-up, but the accreted stars quickly disperse. I will present advanced dynamical models that can convert the observed positions and velocities of stars to phase-space quantities like energy and angular momentum which remain largely conserved. In addition, these models can include the observed ages and chemical properties of stars which are also conserved. The resulting population-dynamical models allow us then to uncover even those accretion events which are now fully dispersed. At the same time, these models also accurately constrain the total mass distribution, including a central black hole and dark matter halo.

I will illustrate how these models make optimally use of observations to unveil the dark side and colour past of galaxies: from accurate measurements of their central black holes and extended dark halos, to unveiling the formation history of their disks, to uncovering ancient massive mergers and accreted satellite galaxies. By the end, I aim to have demonstrated that these models provide a unique bridge between the studies of resolved stars in the Milky Way and integrated-light of high(er)-redshift galaxies. Together with direct coupling to state-of-the-art galaxy formation simulations, these population-dynamical models enable us to uncover the hierarchical build-up of galaxies in a cosmological context.

I will present recent simulation results on AI-based AO reconstructors and time-resolved wavefront sensing, as well as experimental results obtained with REVOLT, the AO test-bench we have on our local 1.2m telescope, including fiber injection of AO corrected light and open-loop AO.

Ultra-diffuse galaxies (UDGs) are extremely low-surface brightness galaxies with a size of several kpc, i.e. comparable to that of the Milky Way, but with at least 100 times smaller stellar masses. In the scope of the LEWIS large programme with VLT-MUSE, we have targeted a complete sample of 32 UDG candidates in the 50-Mpc distant Hydra I cluster. In this talk, I will focus on UDG 32, a galaxy that has been hypothesised to have formed from material stripped from the nearby spiral galaxy NGC 3314a. Our new MUSE data show that NGC 3314a's filaments extend to unprecedented distances, completely engulfing the UDG and confirm that the UDG and the filaments are indeed co-spatial based in position-velocity space. UDG 32 may thus be one of the first ultra-diffuse galaxies where we catch the formation from ram-pressure stripped gas in the act.

The Central Molecular Zone (CMZ) is an extreme environment in the inner few hundred parsecs of the Milky Way Galaxy, with temperatures, pressures, and densities exceeding those measured in the Galactic disk. At a distance of ~8.2 kpc, it has previously been difficult to perform large surveys of the CMZ at high resolution, limiting most studies to individual molecular clouds. ACES (the ALMA CMZ Exploration Survey) is a large ALMA program with high sensitivity observations covering the entire area of the CMZ at high spatial and spectral resolution at 3mm in both continuum and spectral lines. ACES data will be used to determine the overall distribution and chemical composition of mass in the inner Galaxy, from the sub-parsec scales of star formation, to the large-scale global processes that influence it. In addition, spectral line data will be used to create a comprehensive picture of gas kinematics in the CMZ, unveiling how gas flows from galactocentric radii of a few hundred pc down to the vicinity of the central supermassive black hole. Observations and high resolution hydrodynamical simulations will be used in tandem to determine how different physical processes impact the evolution of gas at different scales. We present early science results from the ACES team, including an overview of the data products, the properties of compact sources extracted using ACES continuum data, the rich chemical composition identified in the CMZ, and the characterization of gas kinematics in the CMZ.