Title: A3COSMOS: A census on the gas content of star-forming galaxies across cosmic time
Speaker: Tsan-Ming Wang (Uni. Bonn)
Date: October 06 at 14:30
Location: R521, General Building II
Abstract:
Aims: We aim to understand the underlying mechanisms that trigger the evolution of mass-complete $M_{\star}$>10$^{9.5}M_{\odot}$ star-forming galaxies (SFGs) at 0.4<$z$<3.6.
Methods: We employ an innovative uv-domain stacking analysis on archival data from the Atacama Large Millimeter/submillimeter Array (ALMA) using a mass-complete sample of SFGs. This stacking analysis, focused on the Rayleigh-Jeans dust continuum emission, yields precise measurements of the mean mass and size of the molecular gas in SFGs. Additionally, we apply an image-domain stacking analysis to the optical images of the selected SFGs to trace the distribution of their stellar components.
Results: Across all stellar masses, the molecular gas fraction for the majority of SFGs decreases by a factor of $\sim$24 from $z\sim$3.2 to $z\sim$0. Their molecular gas depletion time and size, however, remain almost constant from$z\sim$3.2 to $z\sim$0.5. As SFGs move to the starburst region, their molecular gas fraction increases by a factor of $\sim$2.1 while their depletion time decreases by a factor of $\sim$3.3. Moreover, their gas size becomes more compact, which is associated with a transformation in their optical morphology.
Conclusions: To first order, the molecular gas content predominantly regulates the star formation of most SFGs throughout cosmic time, with variations in their star formation efficiency playing a secondary role. Our results align with the scenario wherein HI gas from the reservoir flows into the gravitational well of merging systems and subsequently transforms into molecular gas during the merger.
