Redshift evolution of stellar mass versus gas fraction relation in 0<z<2 regime: observational constraint for galaxy formation models

TL;DR

This study examines how the molecular gas fraction in galaxies evolves from redshift 0 to 2, revealing mass-dependent depletion patterns and comparing observations with galaxy formation models.

Contribution

It provides observational constraints on the evolution of molecular gas fractions and highlights discrepancies with theoretical models, emphasizing feedback processes.

Findings

Massive galaxies deplete their molecular gas by z=1.

Less massive galaxies show a drastic decrease in f_mol from z=1.

Models tend to underestimate f_mol, especially for very massive and less massive galaxies.

Abstract

We investigate the redshift evolution of the molecular gas mass fraction (f_mol=M_mol/(M_star+M_mol), where M_mol is molecular gas mass and M_star is stellar mass) of galaxies in the redshift range of 0<z<2 as a function of the stellar mass by combining CO literature data. We observe a stellar-mass dependence of the f_mol evolution where massive galaxies have largely depleted their molecular gas at z=1, whereas the f_mol value of less massive galaxies drastically decreases from z=1. We compare the observed M_star-f_mol relation with theoretical predictions from cosmological hydrodynamic simulations and semi-analytical models for galaxy formation. Although the theoretical studies approximately reproduce the observed mass dependence of f_mol evolution, they tend to underestimate the f_mol values, particularly of less massive (<10^10 Msun) and massive galaxies (>10^11 Msun) when compared with the observational values. Our result suggests the importance of the feedback models which suppress the star formation while simultaneously preserving the molecular gas in order to reproduce the observed M_star-f_mol relation.