A decrease of the gas exchanges between galaxies and the IGM, from 12 to 6 billion years ago

TL;DR

This study investigates the evolution of gas exchange between galaxies and the intergalactic medium over the last 11 billion years, revealing a decline in gas outflows and a linear increase in gas fraction with redshift.

Contribution

It provides new empirical data on gas fractions and outflow rates in intermediate mass galaxies from z~0.6 to higher redshifts, highlighting the evolution of galaxy gas content over cosmic time.

Findings

Gas fraction was twice as high 6 billion years ago compared to today.

Less than 4% of galaxies at z~0.6 show outflow events, unlike at higher redshifts.

Gas and metal co-evolution supports a closed-system galaxy evolution scenario.

Abstract

Using a representative sample of 65 intermediate mass galaxies at z \sim 0.6, we have inves- tigated the interplay between the main ingredients of chemical evolution: metal abundance, gas mass, stellar mass and SFR. All quantities have been estimated using deep spectroscopy and photometry from UV to IR and assuming an inversion of the Schmitt-Kennicutt law for the gas fraction. Six billion years ago, galaxies had a mean gas fraction of 32% \pm 3, i.e. twice that of their local counterparts. Using higher redshift samples from the literature, we explore the gas-phases and estimate the evolution of the mean gas fraction of distant galaxies over the last 11 Gy. The gas fraction increases linearly at the rate of 4% per Gyr from z \sim 0 to z \sim 2.2. We also demonstrate for a statistically representative sample that < 4% of the z \sim 0.6 galaxies are undergoing outflow events, in sharp contrast with z \sim 2.2 galaxies. The observed co-evolution of metals and gas over the past 6 Gyr favours a scenario in which the population of intermediate mass galaxies evolved as closed-systems, converting their own gas reservoirs into stars.