Artículos de revistas
On the selection of damped Lyman α systems using Mg II absorption at 2 < zabs < 4
Fecha
2017-01Registro en:
MNRAS 464, L56–L60 (2017)
10.1093/mnrasl/slw185
Autor
Berg, T. A. M.
Ellison, S. L.
Prochaska, J. X.
Sánchez Ramírez, R.
López Morales, Sebastián
D'Odorico, V.
Becker, G.
Christensen, L.
Cupani, G.
Denney, K.
Worseck, G.
Institución
Resumen
The XQ-100 survey provides optical and near-infrared coverage of 36 blindly selected, intervening damped Lyman alpha systems (DLAs) at 2 < z(abs) < 4, simultaneously covering the MgII doublet at lambda lambda 2796, 2803 angstrom, and the Ly alpha transition. Using the XQ-100 DLA sample, we investigate the completeness of selecting DLA absorbers based on their MgII rest-frame equivalent width (W-0(2796) 0) at these redshifts. Of the 29 DLAs with clean MgII profiles, we find that six (20 per cent of DLAs) have W-0(2796) 0 < 0.6 angstrom. The DLA incidence rate of W-0(2796) 0 < 0.6 angstrom absorbers is a factor of similar to 5 higher than what is seen in z similar to 1 samples, indicating a potential evolution in the MgII properties of DLAs with redshift. All of the W-0(2796) 0 < 0.6 angstrom DLAs have low metallicities (-2.5 < [M/H] < -1.7), small velocity widths (v(90) < 50 km s(-1)), and tend to have relatively low N(H I). We demonstrate that the exclusion of these low W-0(2796) 0 DLAs results in a higher mean N(H I) which in turn leads to an similar to 7 per cent increase in the cosmological gas density of HI of DLAs at 2 < z(abs) < 4; and that this exclusion has a minimal effect on the H I-weighted mean metallicity.