Highest Redshift Image of Neutral Hydrogen in Emission: A CHILES Detection of a Starbursting Galaxy at z=0.376

TL;DR

This paper reports the first detection of neutral hydrogen emission at z=0.376, providing insights into galaxy gas content and interactions at higher redshifts, using data from the CHILES survey.

Contribution

It presents the highest redshift HI emission detection in a galaxy, combining HI and CO observations to study galaxy gas properties beyond z=0.2.

Findings

Detected HI in a galaxy at z=0.376 with asymmetric distribution

Galaxy is rich in molecular hydrogen, with CO observations

HI distribution suggests interaction with a companion

Abstract

Our current understanding of galaxy evolution still has many uncertainties associated with the details of accretion, processing, and removal of gas across cosmic time. The next generation of radio telescopes will image the neutral hydrogen (HI) in galaxies over large volumes at high redshifts, which will provide key insights into these processes. We are conducting the COSMOS HI Large Extragalactic Survey (CHILES) with the Karl G. Jansky Very Large Array, which is the first survey to simultaneously observe HI from z=0 to z~0.5. Here, we report the highest redshift HI 21-cm detection in emission to date of the luminous infrared galaxy (LIRG) COSMOS J100054.83+023126.2 at z=0.376 with the first 178 hours of CHILES data. The total HI mass is $(2.9\pm1.0)\times10^{10}~M_\odot$, and the spatial distribution is asymmetric and extends beyond the galaxy. While optically the galaxy looks undisturbed, the HI distribution suggests an interaction with candidate a candidate companion. In addition, we present follow-up Large Millimeter Telescope CO observations that show it is rich in molecular hydrogen, with a range of possible masses of $(1.8-9.9)\times10^{10}~M_\odot$. This is the first study of the HI and CO in emission for a single galaxy beyond z~0.2.