Issue |
A&A
Volume 552, April 2013
|
|
---|---|---|
Article Number | A77 | |
Number of page(s) | 25 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/201220042 | |
Published online | 29 March 2013 |
The evolution of H i and C iv quasar absorption line systems at 1.9 < z < 3.2 ⋆,⋆⋆
1
Leibniz-Institut für Astrophysik Potsdam,
An der Sternwarte 16,
14482
Potsdam,
Germany
2
Department of Astronomy, University of
Wisconsin-Madison, 475 N. Charter
St., Madison,
WI
53706,
USA
e-mail:
kim@astro.wisc.edu
3
Institute of Astronomy, Madingley Road, Cambridge
CB3 0HA,
UK
Received:
17
July
2012
Accepted:
10
February
2013
We have investigated the distribution and evolution of ~3100 intergalactic neutral hydrogen (H i) absorbers with H i column densities log NH i = [12.75,17.0] at 1.9 < z < 3.2, using 18 high resolution, high signal-to-noise quasar spectra obtained from the ESO VLT/UVES archive. We used two sets of Voigt profile fitting analysis, one including all the available high-order Lyman lines to obtain reliable H i column densities of saturated lines, and another using only the Lyα transition. There is no significant difference between the Lyα-only fit and the high-order Lyman fit results. Combining our Lyα-only fit results at 1.7 < z < 3.6 with high-quality literature data, the mean number density at 0 < z < 4 is not well described by a single power law and strongly suggests that its evolution slows down at z ≤ 1.5 at the high and low column density ranges. We also divided our entire H i absorbers at 1.9 < z < 3.2 into two samples, the unenriched forest and the C iv-enriched forest, depending on whether H i lines are associated with C iv at log NC iv ≥ 12.2 within a given velocity range. The entire H i column density distribution function (CDDF) can be described as the combination of these two well-characterised populations which overlap at log NH i ~ 15. At log NH i ≤ 15, the unenriched forest dominates, showing a similar power-law distribution to the entire forest. The C iv-enriched forest dominates at log NH i ≥ 15, with its distribution function as ∝NH i~−1.45. However, it starts to flatten out at lower NH i, since the enriched forest fraction decreases with decreasing NH i. The deviation from the power law at log NH i = [14,17] shown in the CDDF for the entire H i sample is a result of combining two different H i populations with a different CDDF shape. The total H i mass density relative to the critical density is ΩH i ~ 1.6 × 10-6 h-1, where the enriched forest accounts for ~40% of ΩH i.
Key words: quasars: absorption lines / cosmology: observations / large-scale structure of Universe
The data used in this study are taken from the ESO archive for the UVES at the VLT, ESO, Paranal, Chile.
Appendix A is available in electronic form at http://www.aanda.org
© ESO, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.