On the selection of damped Lyman α systems using Mg II absorption at 2 〈 z<SUB>abs</SUB> 〈 4

DOI: 
10.1093/mnrasl/slw185
Publication date: 
01/01/2017
Main author: 
Berg, T. A. M.
IAA authors: 
Sánchez-Ramírez, R.
Authors: 
Berg, T. A. M.;Ellison, S. L.;Prochaska, J. X.;Sánchez-Ramírez, R.;Lopez, S.;D'Odorico, V.;Becker, G.;Christensen, L.;Cupani, G.;Denney, K.;Worseck, G.
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Volume: 
464
Pages: 
L56-L60
Abstract: 
The XQ-100 survey provides optical and near-infrared coverage of 36 blindly selected, intervening damped Lyman α systems (DLAs) at 2 〈 z<SUB>abs</SUB> 〈 4, simultaneously covering the Mg II doublet at λλ2796, 2803Å, and the Ly α transition. Using the XQ-100 DLA sample, we investigate the completeness of selecting DLA absorbers based on their Mg II rest-frame equivalent width (W<SUB>0</SUB>^{2796}) at these redshifts. Of the 29 DLAs with clean Mg II profiles, we find that six (20 per cent of DLAs) have W<SUB>0</SUB>^{2796} 〈 0.6 Å. The DLA incidence rate of W<SUB>0</SUB>^{2796} 〈 0.6 Å absorbers is a factor of ̃5 higher than what is seen in z ̃ 1 samples, indicating a potential evolution in the Mg II properties of DLAs with redshift. All of the W<SUB>0</SUB>^{2796} 〈 0.6 Å DLAs have low metallicities (-2.5 〈 [M/H] 〈 -1.7), small velocity widths (v<SUB>90</SUB> 〈 50 km s<SUP>-1</SUP>), and tend to have relatively low N(H I). We demonstrate that the exclusion of these low W<SUB>0</SUB>^{2796} DLAs results in a higher mean N(H I) which in turn leads to an ̃7 per cent increase in the cosmological gas density of H I of DLAs at 2 〈 z<SUB>abs</SUB> 〈 4; and that this exclusion has a minimal effect on the H I-weighted mean metallicity.
Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85022201432&doi=10.1093%2fmnrasl%2fslw185&partnerID=40&md5=6dce589cb8b9282fd57c0d4b4ccfca4c
ADS Bibcode: 
2017MNRAS.464L..56B
Keywords: 
galaxies: abundances;galaxies: high-redshift;galaxies: ISM;quasars: absorption lines;Astrophysics - Astrophysics of Galaxies;Astrophysics - Cosmology and Nongalactic Astrophysics