Gaia-assisted selection of a quasar reddened by dust in an extremely-strong Damped Lyman-α Absorber at z=2.226

Abstract

Damped Lyman-α Absorbers (DLAs) as a class of QSO absorption-line systems are currently our most important source of detailed information on the cosmic chemical evolution of galaxies. However, the degree to which this information is biased by dust remains to be understood. One strategy is to specifically search for QSOs reddened by metal-rich and dusty foreground absorbers. In this Letter we present the discovery of a z=2.60 QSO strongly reddened by dust in an intervening extremely-strong DLA at z=2.226. This QSO was identified through a novel selection combining the astrometric measurements from ESA's Gaia satellite with extent optical and near/mid-infrared photometry. We infer a total neutral atomic-hydrogen column density of log N(HI)=21.95{\pm}0.15 and a lower limit on the gas-phase metallicity of [Zn/H]>-0.96. This DLA is also remarkable in exhibiting shielded neutral gas witnessed in CI and tentative detections of CO molecular bands. The Spectral Energy Distribution (SED) of the QSO is well-accounted for by a normal QSO-SED reddened by dust from a DLA with a 10%-of-Solar metallicity, dust extinction of A_V=0.82{\pm}0.02mag, and LMC-like extinction curve including the characteristic 2175Å extinction feature. Such QSO absorption-line systems have shown to be very rare in previous surveys, which have mostly revealed sight-lines with low extinction. The present case therefore suggests that previous samples have under-represented the fraction of dusty absorbers. Building a complete sample of such systems is needed to assess the significance of this effect.

5 pages, 4 figures, 2 tables. Submitted to A&A Letters, revised version after referee reports

References in corpus (14)

• The First Positive Detection of Molecular Gas in a GRB Host Galaxy
• Voigt Profile Fitting to Quasar Absorption Lines: An Analytic Approximation to the Voigt-Hjerting Function
• Extremely Red Quasars in BOSS
• Heavily reddened type 1 quasars at z > 2 I: Evidence for significant obscured black-hole growth at the highest quasar luminosities
• A connection between extremely strong Damped Lyman-alpha Systems and Lyman-alpha Emitting Galaxies at small impact parameters
• The UCSD Radio-Selected Quasar Survey for Damped Lyman alpha System
• Optical/near-infrared selection of red QSOs: Evidence for steep extinction curves towards galactic centers?
• Statistical properties of damped Lyman-alpha systems from Sloan Digital Sky Survey DR12
• Chemical abundances of damped Lyman alpha systems in the XQ-100 survey
• Dust Biasing of Damped Lyman Alpha Systems: a Bayesian Analysis
• The High A(V) Quasar Survey: Reddened quasi-stellar objects selected from optical/near-infrared photometry - II
• The elusive HI-> H2 transition in high-z damped Lyman-alpha systems
• The high A_V Quasar Survey: A z=2.027 metal-rich damped Lyman-alpha absorber towards a red quasar at z=3.21
• A study of purely astrometric selection of extragalactic point sources with Gaia

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• A successful search for intervening 21 cm HI absorption in galaxies at 0.4 < z <1.0 with the Australian Square Kilometre Array Pathfinder (ASKAP)
• J1721$+$8842: a gravitationally lensed binary quasar with a proximate damped Lyman-$\alpha$ absorber
• The galaxy counterpart and environment of the dusty Damped Lyman-alpha Absorber at z=2.226 towards Q1218+0832
• Serendipitous discovery of a physical binary quasar at z=1.76
• On the Dusty Proximate Damped Lyman-α System toward Q2310-3358 at z = 2.40