Astronomy & Astrophysics Seminar: Molecular gas reservoirs during the winding-down of star formation

Abstract:

Star formation in the Universe decreased by an order of magnitude in the last ten billion years. The PHIBSS2 program at the IRAM NOEMA interferometer surveys the molecular gas from which stars are formed within galaxies at different redshifts on and around the main sequence, where most of star formation occurs. At z=0.5-0.8, we observe the CO(2-1) line for 61 targets, from which we determine molecular gas masses, gas fractions and depletion times. Our results contribute to show that the cosmic evolution of the star formation rate is mainly driven by that of the molecular gas fraction, albeit with a small inflexion of the star formation efficiency. We further obtain disk sizes and bulge-to-total luminosity ratios, pointing towards little dependence of the molecular gas content and star formation with bulge size. This may suggest an ongoing supply of molecular gas to compensate for star formation and a contribution of disk stars to the growing bulge. Ongoing NOEMA and ALMA projects complement this program with molecular gas measurements below the main sequence and in different types of environments. 

Seminar Organizer: Prof. Sara Beck