A survey of Ly$\alpha$ emission around Damped Ly$\alpha$ absorbers at $z\approx 2$ with the Keck Cosmic Web Imager

Abstract

We present Keck Cosmic Web Imager (KCWI) Ly$\alpha$ integral field spectroscopy of the fields surrounding 14 Damped Ly$\alpha$ absorbers (DLAs) at $z\approx 2$. Of these 14 DLAs, 9 have high metallicities ([M/H]$>-0.3$), and 4 of those 9 feature a CO-emitting galaxy at an impact parameter $\lesssim 30$ kpc. Our search reaches median Ly$\alpha$ line flux sensitivities of $\sim 2\times 10^{-17}$ erg s${}^{-1}$ cm${}^{-2}$ over apertures of $\sim 6$ kpc and out to impact parameters of $\sim 50$ kpc. We recover the Ly$\alpha$ flux of three known Ly$\alpha$-emitting H I-selected galaxies in our sample. In addition, we find two Ly$\alpha$ emitters at impact parameters of $\approx 50-70$ kpc from the high metallicity DLA at $z\approx 1.96$ toward QSO B0551-366. This field also contains a massive CO-emitting galaxy at an impact parameter of $\approx 15$ kpc. Apart from the field with QSO B0551-366, we do not detect significant Ly$\alpha$ emission in any of the remaining 8 high-metallicity DLA fields. Considering the depth of our observations and our ability to recover previously known Ly$\alpha$ emitters, we conclude that H I-selected galaxies associated with high-metallicity DLAs at $z\approx 2$ are dusty, and therefore might feature low Ly$\alpha$ escape fractions. Our results indicate that complementary approaches -- using Ly$\alpha$, CO, H$\alpha$, and [C II] 158$\mu$m emission -- are necessary to identify the wide range of galaxy types associated with $z\approx 2$ DLAs.

Accepted for publication in ApJ. 17 pages and 9 figures. Second version with corrections prior to publication

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