A Survey of Lyα Emission around Damped Lyα Absorbers at z ≈ 2 with the Keck Cosmic Web Imager

Abstract

We present Keck Cosmic Web Imager Ly α integral field spectroscopy of the fields surrounding 14 damped Ly α absorbers (DLAs) at z ≈ 2. Of these 14 DLAs, nine have high metallicities ([M/H] > − 0.3), and four of those nine feature a CO-emitting galaxy at an impact parameter ≲30 kpc. Our search reaches median Ly α line flux sensitivities of ∼2 × 10 ^−17 erg s ^−1 cm ^−2 over apertures of ∼6 kpc and out to impact parameters of ∼50 kpc. We recover the Ly α flux of three known Ly α -emitting H i -selected galaxies in our sample. In addition, we find two Ly α emitters at impact parameters of ≈50–70 kpc from the high-metallicity DLA at z ≈ 1.96 toward QSO B0551-366. This field also contains a massive CO-emitting galaxy at an impact parameter of ≈15 kpc. Apart from the field with QSO B0551-366, we do not detect significant Ly α emission in any of the remaining eight high-metallicity DLA fields. Considering the depth of our observations and our ability to recover previously known Ly α emitters, we conclude that H i -selected galaxies associated with high-metallicity DLAs at z ≈ 2 are dusty and therefore might feature low Ly α escape fractions. Our results indicate that complementary approaches—using Ly α , CO, H α , and [C ii ] 158 μ m emission—are necessary to identify the wide range of galaxy types associated with z ≈ 2 DLAs.

Keywords

• Galaxy evolution
• Galaxy formation
• Damped Lyα systems
• Lyα galaxies
• Galaxies
• Quasars