CHILES XII: The H I evolution of Luminous Compact Blue Galaxies between 0<z<0.48

TL;DR

This study investigates the H I gas content evolution of Luminous Compact Blue Galaxies up to redshift 0.48 using the CHILES survey, finding no significant change in gas mass over time.

Contribution

It provides the first direct measurements of H I mass in LCBGs across this redshift range, revealing their gas reservoirs remain substantial and consistent with star-forming galaxies.

Findings

Average H I mass estimates at different redshifts show no strong evolution.

LCBGs retain significant gas reservoirs with constant gas fractions.

Gas depletion timescales are much shorter than in normal star-forming galaxies.

Abstract

We study the evolution of Luminous Compact Blue Galaxies (LCBGs) by making use of H I emission line data provided by the full 856 h COSMOS H I Large Extragalactic Survey (CHILES), which spans a redshift range of $0\leq z\leq 0.48$ within the COSMOS field. We report the results on a cubelet stacking analysis, which we use to estimate the average H I mass evolution of LCBGs in the field up to $z=0.48$. For the stacks that do not show a detection, we report an upper limit estimate of the average H I mass. We also report on two directly detected LCBGs. We find the average H I mass in LCBGs at redshifts $z=0.26$, $z=0.35$ and $z=0.45$ respectively to be $\langle M_{\rm HI}\rangle<4.89\times10^9$ M$_\odot$, $\langle M_{\rm HI}\rangle=(2.49\pm0.75)\times10^9$ M$_\odot$ and $\langle M_{\rm HI}\rangle=(6.44\pm2.71)\times10^9$ M$_\odot$. We see no strong evidence for evolution in the average H I mass over this redshift range, consistent with other recent studies of the evolution of the H I in galaxies at $z<0.5$. On average, LCBGs appear to retain substantial gas reservoirs, with gas fractions staying constant and remaining broadly consistent with those of the larger star-forming population. LCBG gas depletion timescales are nearly an order of magnitude shorter than in normal star-forming galaxies across the studied redshift range, aligning with the period during which their number density drops sharply.