Mon. Not. R. Astron. Soc., 455, 1043-1059 (2016/January-1)
The dust content of damped Lyman α systems in the Sloan Digital Sky Survey.
MURPHY M.T. and BERNET M.L.
Abstract (from CDS):
The dust content of damped Lyman α systems (DLAs) is an important observable for understanding their origin and the neutral gas reservoirs of galaxies. While the average colour excess of DLAs, E(B - V), is known to be ≲ 15 millimagnitude (mmag), both detections and non-detections with ∼ 2 mmag precision have been reported. Here we find 3.2σ statistical evidence for DLA dust-reddening of 774 Sloan Digital Sky Survey (SDSS) quasars by comparing their fitted spectral slopes to those of ∼ 7000 control quasars. The corresponding E(B - V) is 3.0±1.0 mmag, assuming a Small Magellanic Cloud (SMC) dust extinction law, and it correlates strongly (3.5σ) with the metal content, characterized by the Si II λ1526 absorption-line equivalent width, providing additional confidence that the detection is due to dust in the DLAs. Evolution of E(B - V) over the redshift range 2.1 < z < 4.0 is limited to <2.5 mmag per unit redshift (1σ), consistent with the known, mild DLA metallicity evolution. There is also no apparent relationship with neutral hydrogen column density, N_H I, though the data are consistent with a mean E(B¡-¡V)/N_H I=(3.5±1.0)×10^-24 mag cm2, approximately the ratio expected from the SMC scaled to the lower metallicities typical of DLAs. We implement the SDSS selection algorithm in a portable code to assess the potential for systematic, redshift-dependent biases stemming from its magnitude and colour-selection criteria. The effect on the mean E(B - V) is negligible (<5 per cent) over the entire redshift range of interest. Given the broad potential usefulness of this implementation, we make it publicly available.
© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2015)
dust, extinction - galaxies: high redshift - intergalactic medium - galaxies: ISM - quasars: absorption lines
VizieR on-line data:
<Available at CDS (J/MNRAS/455/1043): table1.dat table2.dat table3.dat table4.dat>
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