Directly imaging damped Lyman-alpha galaxies at z>2. I: Methodology and First Results

Abstract

We present the methodology for, and the first results from, a new imaging program aimed at identifying and characterizing the host galaxies of damped Lyman-alpha absorbers (DLAs) at z>2. We target quasar sightlines with multiple optically-thick HI absorbers and use the higher-redshift system as a "blocking filter" (via its Lyman-limit absorption) to eliminate all far-ultraviolet (FUV) emission from the quasar. This allows us to directly image the rest-frame FUV continuum emission of the lower-redshift DLA, without any quasar contamination and with no bias towards large impact parameters. We introduce a formalism based on galaxy number counts and Bayesian statistics with which we quantify the probability that a candidate is the DLA host galaxy. This method will allow the identification of a bona fide sample of DLAs that are too faint to be spectroscopically confirmed. The same formalism can be adopted to the study of other quasar absorption line systems (e.g. MgII absorbers). We have applied this imaging technique to two QSO sightlines. For the z~2.69 DLA towards J073149+285449, a galaxy with impact parameter b=1.54"=11.89 kpc and implied star formation rate (SFR) of ~5 M/yr is identified as the most reliable candidate. In the case of the z~2.92 DLA towards J211444-005533, no likely host is found down to a 3-sigma SFR limit of 1.4 M/yr. Studying the HI column density as a function of the impact parameter, including 6 DLAs with known hosts from the literature, we find evidence that the observed HI distribution is more extended than what is generally predicted from numerical simulation.

22 pages, 13 figures. Accepted for publication in MNRAS. Typos corrected

References in corpus (18)

• EAZY: A Fast, Public Photometric Redshift Code
• Cold streams in early massive hot haloes as the main mode of galaxy formation
• UV Star Formation Rates in the Local Universe
• Forming Disk Galaxies in Lambda CDM Simulations
• The rapid formation a large rotating disk galaxy three billion years after the Big Bang
• On the (Non)Evolution of HI Disks over Cosmic Time
• The GOODS-MUSIC sample: a multicolour catalog of near-IR selected galaxies in the GOODS-South field
• A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems
• Damped Lyman Alpha Systems in Galaxy Formation Simulations
• Quasars Probing Quasars II: The Anisotropic Clustering of Optically Thick Absorbers around Quasars
• The Cosmic Decline in the H2/HI-Ratio in Galaxies
• The Keck+Magellan Survey for Lyman Limit Absorption I: The Frequency Distribution of Super Lyman Limit Systems
• Searching for Low Surface-brightness Galaxies in the Hubble Ultra Deep Field: Implications for the Star Formation Efficiency in Neutral Gas at z ~ 3
• A blind test of photometric redshifts on ground-based data
• Environmental dependence of AGN activity in the supercluster A901/2
• A new comprehensive set of elemental abundances in DLAs III. Star formation histories
• An integral field spectroscopic survey for high redshift damped Lyman-alpha galaxies
• A Shot in the Dark: A Technique for Locating the Stellar Counterparts of Damped Lyman Alpha Absorbers

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• Directly imaging damped Ly-alpha galaxies at z>2. III: The star formation rates of neutral gas reservoirs at z~2.7
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• HI 21cm emission from the sub-damped Lyman-alpha absorber at z=0.0063 towards PG1216+069
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