A metal-line strength indicator for damped Lyman alpha (DLA) systems at low signal-to-noise

0545811 - ÚI 2022 GB eng J - Journal Article
Arinyo i Prats, Andreu - Mas Ribas, L. - Miralda Escude, J. - Perez Rafols, I. - Noterdaeme, P.
A metal-line strength indicator for damped Lyman alpha (DLA) systems at low signal-to-noise.
Monthly Notices of the Royal Astronomical Society. Roč. 481, č. 3 (2018), s. 3921-3934. ISSN 0035-8711. E-ISSN 1365-2966
Keywords : abundance database * galaxies * metallicity * absorption * kinematics * telescope * bias * catalogues * surveys * intergalactic medium * quasars: absorption lines * early Universe
Impact factor: 5.231, year: 2018

The bias factor of damped Ly alpha (DLAs) systems, derived from the cross-correlation with the Ly alpha forest in absorption spectra of the Baryon Oscillation Spectroscopic Survey of SDSS-III, has been used to infer the characteristic mass of DLA host haloes. So far, no dependence of this bias factor with hydrogen column density N-HI or other parameters has been detected. With the aim of measuring the dependence of the bias factor on the strength of metal lines, we define the metal strength parameter S, based on optimally combining equivalent widths of 17 metal lines to obtain the highest possible signal-to-noise ratio of S for individual candidate DLAs (defined as having N-HI >= 10(20) cm(-2)). We present the distribution of metal strength for these DLAs and the dependence of its mean value on N-HI and redshift. We search for systematic effects and variations in the catalogue purity by examining the dependence of the S distribution on the spectral signal-to-noise and the estimated error on S. A catalogue of DLAs with measured equivalent widths for the selected 17 metal lines and the value of S are made publicly available, which are used in a separate paper to measure the dependence of the DLA bias factor on the S parameter. The relation of the metal strength on the gas metal abundances and velocity dispersion is complicated by the saturation of metal lines, and remains to be determined in future work.
Permanent Link: http://hdl.handle.net/11104/0322456