# [CII] 158 Micron Emission from z~4 HI Absorption-Selected Galaxies

## TL;DR

This study uses ALMA to detect [CII] 158 micron emission from galaxies at z~4 associated with high-metallicity DLAs, revealing properties similar to luminous Lyman-break galaxies and showing that DLAs trace gas in these galaxies.

## Contribution

First detection of [CII] emission from high-metallicity DLA galaxies at z~4, linking absorption features to galaxy emission properties.

## Key findings

- [CII] emission detected in 5 of 6 targeted galaxies.
- Galaxies have star-formation rates of 7-110 solar masses per year.
- Absorption and emission line velocities are aligned, indicating the DLA gas is in the galaxy itself.

## Abstract

We report on a search for the [CII] 158 micron emission line from galaxies associated with four high-metallicity damped Ly-alpha absorbers (DLAs) at z ~ 4 using the Atacama Large Millimeter/sub-millimeter Array (ALMA). We detect [CII] 158 micron emission from galaxies at the DLA redshift in three fields, with one field showing two [CII] emitters. Combined with previous results, we now have detected [CII] 158 micron emission from five of six galaxies associated with targeted high-metallicity DLAs at z ~ 4. The galaxies have relatively large impact parameters, ~16 - 45 kpc, [CII] 158 micron line luminosities of (0.36 - 30) x 10^8 Lsun, and rest-frame far-infrared properties similar to those of luminous Lyman-break galaxies, with star-formation rates of ~7 - 110 Msun yr-1. Comparing the absorption and emission line profiles yields a remarkable agreement between the line centroids, indicating that the DLA traces gas at velocities similar to that of the [CII] 158 micron emission. This disfavors a scenario where the DLA arises from gas in a companion galaxy. These observations highlight ALMA's unique ability to uncover a high redshift galaxy population that has largely eluded detection for decades.