Seminars and Colloquia at ESO Garching and on the campus

Neutral atomic hydrogen (HI) plays a crucial role in galaxy evolution as a major component of the cold gas reservoir of galaxies that fuels star formation. The HI disk, however, typically extends well beyond the stellar disc where the majority of the star formation occurs, and the limited spatial resolution of single-dish observations has constrained our understanding of the interplay between gas and other galactic properties on a co-spatial scale. The Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY) will be a breakthrough, providing a statistical sample of spatially resolved HI data that offers us information about the distribution of the HI in the galactic disc. Using 841 galaxies from the WALLABY pilot surveys, we focus on the stellar disk, where star formation is concentrated. Within this region, HI depletion times are shorter and show a stronger correlation with stellar surface density, highlighting stellar density as a key regulator of HI-to-H₂ conversion. In contrast, HI in the outer disk is consumed on timescales of tens to hundreds of billions of years, confirming its inefficiency as star-forming fuel. These results emphasize the critical role of spatial location and local conditions in determining how HI contributes to star formation.

It is well established that SNe Ia are caused by the thermonuclear explosion of CO white dwarfs. However, there is still a lot of uncertainty about their progenitor channel(s) and explosion mechanism(s). "Bumps" in the early light curves of SN Ia were predicted to occur when the SN ejecta shocks the non-degenerate binary companion (Kasen 2010), thus providing evidence for the single-degenerate (SD) progenitor channel. However, after several examples of these bumps were found, it is still debated if this is indeed evidence for the SD channel, or whether other progenitor channels and explosion mechanism can also cause such bumps.