Discovery of a Damped Lyα Galaxy at z ∼ 3 toward the Quasar SDSS J011852+040644

Ravi Joshi,Siwei Zou,Raghunathan Srianand,Zheng Cai,Michele Fumagalli,Pasquier Noterdaeme,Xue-Bing Wu,Ruari Mackenzie,D Christopher Martin,Luis C Ho,Qiong Li,Patrick Petitjean,Linhua Jiang,Marc Rafelski

doi:10.3847/1538-4357/abd1d5

Abstract

Abstract We report the detection of the host galaxy of a damped Lyα system (DLA) with log N(H i) [cm−2] = 21.0 ± 0.10 at z ≈ 3.0091 toward the background quasar SDSS J011852+040644 using the Palomar Cosmic Web Imager at the Hale (P200) telescope. We detect Lyα emission in the dark core of the DLA trough at a 3.3σ confidence level, with Lyα luminosity of L Lyα = (3.8 ± 0.8) × 1042 erg s−1, corresponding to a star formation rate of ≳2 M ⊙ yr−1 (considering a lower limit on Lyα escape fraction f esc Ly α ∼ 2 % ) as typical for Lyman break galaxies at these redshifts. The Lyα emission is blueshifted with respect to the systemic redshift derived from metal absorption lines by 281 ± 43 km s−1. The associated galaxy is at very small impact parameter of ≲12 kpc from the background quasar, which is in line with the observed anticorrelation between column density and impact parameter in spectroscopic searches tracing the large-scale environments of DLA host galaxies.

Highlights

The evolution of galaxies is significantly influenced by the physical state of gas in and around the central star-forming regions
Leveraging the observed correlation between luminosity and metallicity in galaxies (Tremonti et al 2004; Ledoux et al 2006; Møller et al 2013; Christensen et al 2014), recent campaigns have focused instead on metal-rich damped Lyα absorbers (DLAs), resulting in a far higher detection rate of ≈65% (Fynbo et al 2010, 2011; Krogager et al 2017; Ranjan et al 2020). In spite of these numerous attempts, only ≈20 DLAs at redshift 2 have been associated directly with counterparts in emission. This low detection rate could be attributed either to the faint nature of DLA galaxies, or to their dusty nature, or to high H I column density, or yet again to the fact that only a fraction of the DLA population is directly connected to active star formation
We report the detection of Lyα emission from the host galaxy of a DLA with log N(H I)[cm−2] = 21.0 ± 0.10 at zabs = 3.0091 toward the background quasar Sloan Digital Sky Survey (SDSS) J011852+040644 at zem = 3.226

Summary

Introduction

The evolution of galaxies is significantly influenced by the physical state of gas in and around the central star-forming regions. In spite of these numerous attempts, only ≈20 DLAs at redshift 2 have been associated directly with counterparts in emission (see Krogager et al 2017) This low detection rate could be attributed either to the faint nature of DLA galaxies (which become difficult to image at close separation from bright background quasars), or to their dusty nature, or to high H I column density, or yet again to the fact that only a fraction of the DLA population is directly connected to active star formation.

Sample Selection

Observations and Data Reduction

Results

Discussion and Conclusion