# Evolution of Interstellar Medium, Star Formation, and Accretion at High Redshift

## TL;DR

This study uses ALMA dust continuum observations to analyze how interstellar medium mass, star formation, and gas accretion evolve in galaxies from redshift 0.3 to 4.5, revealing that early galaxy activity is driven by increased gas mass and efficiency.

## Contribution

It provides new empirical relations between ISM mass, star formation, and redshift, highlighting the role of gas accretion in galaxy evolution at high redshift.

## Key findings

- ISM masses increase with redshift and sSFR
- Star formation efficiency rises with redshift and above the main sequence
- Gas accretion rates are >100 solar masses per year at z > 2.5

## Abstract

ALMA observations of the long wavelength dust continuum are used to estimate the interstellar medium (ISM) masses in a sample of 708 galaxies at z = 0.3 to 4.5 in the COSMOS field. The galaxy sample has known far-infrared luminosities and, hence, star formation rates (SFRs), and stellar masses (M$_{\rm *}$) from the optical-infrared spectrum fitting. The galaxies sample SFRs from the main sequence (MS) to 50 times above the MS. The derived ISM masses are used to determine the dependence of gas mass on redshift, M$_{\rm *}$, and specific SFR (sSFR) relative to the MS. The ISM masses increase approximately 0.63 power of the rate of increase in SFRs with redshift and the 0.32 power of the sSFR/sSFR$_MS$. The SF efficiencies also increase as the 0.36 power of the SFR redshift evolutionary and the 0.7 power of the elevation above the MS; thus the increased activities at early epochs are driven by both increased ISM masses and SF efficiency. Using the derived ISM mass function we estimate the accretion rates of gas required to maintain continuity of the MS evolution ($>100$ \msun yr$^{-1}$ at z $>$ 2.5). Simple power-law dependences are similarly derived for the gas accretion rates. We argue that the overall evolution of galaxies is driven by the rates of gas accretion. The cosmic evolution of total ISM mass is estimated and linked to the evolution of SF and AGN activity at early epochs.