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  • Sub-damped Lyman α systems in the XQ-100 survey – I. Identification and contribution to the cosmological H i budget
Title: Sub-damped Lyman α systems in the XQ-100 survey – I. Identification and contribution to the cosmological H i budget
Abstract Sub-damped Lyman α systems (subDLAs; H i column densities of 19.0 ≤ logN(H i) < 20.3) are rarely included in the cosmic H i census performed at redshifts zabs ≳ 1.5, yet are expected to contribute significantly to the overall H i mass budget of the Universe. In this paper, we present a blindly selected sample of 155 subDLAs found along 100 quasar sightlines (with a redshift path-length ΔX = 475) in the XQ-100 legacy survey to investigate the contribution of subDLAs to the H i mass density of the Universe. The impact of X-Shooter’s spectral resolution on Ly α absorber identification is evaluated, and found to be sufficient for reliably finding absorbers down to a column density of logN(H i) ≥ 18.9. We compared the implications of searching for subDLAs solely using H i absorption versus the use of metal lines to confirm the identification, and found that metal-selection techniques would have missed 75 subDLAs. Using a bootstrap Monte Carlo simulation, we computed the column density distribution function (f(N, X)) and the cosmological H i mass density ($$\Omega _{\rm H\,{\small I}}$$) of subDLAs and compared with our previous work based on the XQ-100 damped Lyman α systems. We do not find any significant redshift evolution in f(N, X) or $$\Omega _{\rm H\,{\small I}}$$ for subDLAs. However, subDLAs contribute 10–20 per cent of the total $$\Omega _{\rm H\,{\small I}}$$ measured at redshifts 2 < z < 5, and thus have a small but significant contribution to the H i budget of the Universe.  more » « less
Award ID(s):
1751404
PAR ID:
10109050
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
488
Issue:
3
ISSN:
0035-8711
Page Range / eLocation ID:
4356 to 4369
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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