[C ii] 158 μ m Emission from z ∼ 4 H i Absorption-selected Galaxies

Abstract

We report on a search for the [C ii] 158 μm emission line from galaxies associated with four high-metallicity damped Lyα absorbers (DLAs) at z ~ 4 using the Atacama Large Millimeter/submillimeter Array (ALMA). We detect [C ii] 158 μm emission from galaxies at the DLA redshift in three fields, with one field showing two [C ii] 158 μm emitters. Combined with previous results, we now have detected [C ii] 158 μm 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, [C ii] 158 μm line luminosities of (0.36–30) × 10⁸ L_⊙, and rest-frame far-infrared properties similar to those of luminous Lyman-break galaxies, with star formation rates of ≈7–110 M_⊙ 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 [C ii] 158 μm 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.