Evolution of Gas Content Through Cosmic History
Fabian Walter (Max-Planck-Institut für Astronomy)
Tuesday 30/10/2018 @ 14:00, Sala IV piano Battiferro
The temporal evolution of the cosmic star formation rate density is now well established out to high redshift. This star formation rate density shows a clear peak at z~1-2 that is about one order of magnitude higher than today. The cause for this behaviour must be driven by the properties of the underlying reservoir of molecular gas, the fuel for star formation galaxies. The last decade has seen dramatic progress in quantifying the molecular gas content in galaxies through cosmic times, through various observational camapigns. I will summarize our current view of the molecular gas content in distant galaxies. This will include some of the recent results emerging from ASPECS: The ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF). This ALMA large program provides a census of molecular gas in high-redshift galaxies through full frequency scans at approximately uniform line sensitivity. The resulting cosmic molecular gas density as a function of redshift shows a factor 3-10 decrease from z=2 to z=0. The cosmic star formation history therefore appears to be at least partly driven by the increased availability of molecular gas reservoirs at the peak of cosmic star formation (z~2).