Luminosity Evolution of the Hot Gas in Normal Galaxies from the Near Universe to z=0.5

TL;DR

This study investigates the evolution of hot gas X-ray luminosity in normal galaxies up to redshift 0.5, revealing a significant decrease over the last 5 billion years and implications for the missing baryon problem.

Contribution

It provides the first detailed analysis of hot gas luminosity evolution in normal galaxies up to z=0.5 using a large Chandra survey sample.

Findings

X-ray luminosity of hot gas decreases by a factor of 6-10 from z=0.5 to 0.1.

Number density of hot gas luminous galaxies increases with redshift.

Results align with models of galaxy evolution involving mass loss and star formation history.

Abstract

We explore the evolution of the ~107 degree hot gas in normal galaxies out to redshift = 0.5 (lookback time = 5 Gyr), using X-ray luminosity functions (XLF) built from a sample of 575 normal galaxies with z < 0.6 detected in five high galactic latitude Chandra wide-field surveys. After estimating the emission due to the hot gas component (reducing the sample to ~400 galaxies), we compared the XLF in three redshift bins (z = 0.1, 0.3, and 0.5), finding increases in the number of galaxies per unit co-moving volume from z = 0.1 to 0.3 and then from z = 0.3 to 0.5. These XLF changes suggest a significant (~5s) X-ray luminosity evolution of the hot gas, with LX,GAS decreasing by a factor of 6-10 in the last 5 Gyr (from z = 0.5 to 0.1). The relative abundance of LX,GAS~1041 erg s-1 galaxies at higher z, suggests that high z, moderate LX,GAS galaxies may be the optimal target to solve the missing baryon problem. In early-type galaxies, this observational trend is qualitatively consistent with (but larger than) the expected time-dependent mass-loss rate in cooling flow models without AGN feedback. In late-type galaxies, the observational trend is also qualitatively consistent with (but larger than) the effect of the z-dependent SFR.