Seminario: Dissecting Gas in Galaxies over Cosmic Time

Speaker: Dr. Jens-Kristian Krogager
Affiliation: Researcher at the French-Chiliean Laboratory for Astrophysics at the Universidad de Chile.

Abstract: An important constituent of galaxies is their gas reservoir, most notably the neutral gas. The neutral gas is crucial for star formation, leading one to expect a correlation between the evolution of the average neutral gas mass density and the average star formation rate. However, over the past 10 billion years, while the average rate of star formation has dropped by about a factor of 10, the neutral gas density hasn’t evolved much. To understand this discrepancy, it’s essential to constrain gas properties over cosmic time and especially the split between neutral and molecular hydrogen. Absorption spectroscopy emerges as a powerful probe of the neutral and molecular gas which is otherwise extremely elusive beyond the local volume.  This talk highlights how absorption spectroscopy enables the study of neutral and molecular gas in galaxies across cosmic distances – from the Milky Way to galaxies at the “cosmic noon” and beyond. Lastly, I will focus on current efforts towards the first blind quasar survey, emphasizing its importance not only for understanding absorption systems but also for gaining broader insights into the evolution of quasars and galaxies.