Large Scale Structure traced by Molecular Gas at High Redshift

TL;DR

This study observes molecular gas in a high-redshift galaxy overdensity, detecting a new molecular gas emitter and placing limits on gas masses in known galaxies, shedding light on early universe structure formation.

Contribution

First detection of a molecular gas emitter in a high-redshift galaxy overdensity, highlighting the importance of optically-faint sources in tracing early universe structure.

Findings

Detected a molecular gas emitter at z=5.1245

Placed upper limits on gas masses of known galaxies

Identified optically-faint molecular gas as key tracers

Abstract

We present observations of redshifted CO(1-0) and CO(2-1) in a field containing an overdensity of Lyman break galaxies (LBGs) at z=5.12. Our Australia Telescope Compact Array observations were centered between two spectroscopically-confirmed z=5.12 galaxies. We place upper limits on the molecular gas masses in these two galaxies of M(H_2) <1.7 x 10^10 M_sun and <2.9 x 10^9 M_sun (2 sigma), comparable to their stellar masses. We detect an optically-faint line emitter situated between the two LBGs which we identify as warm molecular gas at z=5.1245 +/- 0.0001. This source, detected in the CO(2-1) transition but undetected in CO(1-0), has an integrated line flux of 0.106 +/- 0.012 Jy km/s, yielding an inferred gas mass M(H_2)=(1.9 +/- 0.2) x 10^10 M_sun. Molecular line emitters without detectable counterparts at optical and infrared wavelengths may be crucial tracers of structure and mass at high redshift.