Tracing the Cosmic Evolution of the Cool Circumgalactic Medium of Luminous Red Galaxies with DESI Year 1 Data

TL;DR

This study analyzes the evolution and properties of cool circumgalactic gas around luminous red galaxies from redshift 0.4 to 1.2, revealing trends in gas covering fraction, kinematics, and potential origins using DESI Year 1 data.

Contribution

It provides new insights into the redshift evolution, mass dependence, and kinematic components of cool CGM around massive galaxies, based on a large galaxy-quasar pair sample.

Findings

Cool gas covering fraction increases with redshift.

Inner region cool gas is anti-correlated with stellar mass.

Broad velocity component becomes more prominent at larger radii and higher masses.

Abstract

We investigate the properties of the cool circumgalactic medium (CGM) of massive galaxies and their cosmic evolution. By using the year 1 dataset of luminous red galaxies (LRGs) and QSOs from the Dark Energy Spectroscopic Instrument survey, we construct a sample of approximately 600,000 galaxy-quasar pairs and measure the radial distribution and kinematics of the cool gas traced by Mg II absorption lines as a function of galaxy properties from redshift 0.4 to redshift 1.2. Our results show that the covering fraction of the cool gas around LRGs increases with redshift, following a trend similar to the global evolution of galaxy star formation rate. At small radii (< 0.3rvir), the covering fraction anti-correlates with stellar mass, suggesting that mass-dependent processes suppress the cool gas content in the inner region. In addition, we measure the gas dispersion by modeling the velocity distribution of absorbers with a narrow and a broad components -- sigma_n ~ 160 and sigma_b ~ 380 km/s -- and quantify their relative contributions. The results show that the broad component becomes more prominent in the outer region, and its relative importance in the central region grows with increasing stellar mass. Finally, we discuss possible origins of the cool gas around massive galaxies, including the contribution of satellite galaxies and the precipitation scenario.