Tracing the Evolution of Gas and Star Formation Properties along the Offset from the Star-forming Main Sequence

Hsi-An Pan^1*, Lihwai Lin², Sara Ellison³, Mallory Thorp³, Sebastian Sanchez⁴

¹Department of Physics, Tamkang University, New Taipei City, Taiwan
²Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
³Department of Physics and Astronomy, University of Victoria, Victoria, Canada
⁴Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City, Mexico

* Presenter:Hsi-An Pan, email:hapan@gms.tku.edu.tw

Quenching of star formation is one of the key drivers of galaxy evolution. We use 34 galaxies selected from the ALMaQUEST survey to study the change of gas and star formation properties as galaxies moving away from the star-forming main sequence toward the passive regime. Our spatially-resolved analysis shows that the radial profiles of local SFR (Σ_sSFR), molecular gas fraction (f_gas), and star formation efficiency (SFE) show a clear ranking with global sSFR at all the galactic radii we explored, suggesting that star formation quenching is a global phenomenon. The relative roles of f_gas and SFE on ΣsSFR suggests that the loss of molecular gas is primarily responsible for the start of star formation quenching, but SFE is the main driver once the galaxies are quenched to the regime below the main sequence. Moreover, as the molecular gas and star formation continuously vary when galaxies moving away from the main sequence, the appearance of the corresponding scalling relations of galaxies also change gradually. In addition, our integrated analysis favors a scenario that the lower f_gas toward lower-global-sSFR galaxies is a result of decreases in both molecular and atomic gas mass rather than a significant change in molecular-to-atomic gas mass ratio. Finally, we find that the reduce of star formation in the ALMaQUEST sample may be driven by secular (e.g., bar formation) and environmental processes. There is no obvious correlation between the presence of AGN and star formation activity in our sample, but the role of AGN feedback cannot be ruled out completely yet.

Keywords: interstellar medium, star formation, galaxy evolution, galaxy survey