Back to Search
Start Over
The evolution of H I and C IV quasar absorption line systems at 1.9 < z < 3.2.
- Source :
- Astronomy & Astrophysics / Astronomie et Astrophysique; Apr2013, Vol. 552 Issue 2, pA77-A98, 22p
- Publication Year :
- 2013
-
Abstract
- We have investigated the distribution and evolution of ~3100 intergalactic neutral hydrogen (HI) absorbers with H i column densities log N<subscript>HI</subscript> = [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 HI 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 HI absorbers at 1.9 < z < 3.2 into two samples, the unenriched forest and the C<subscript>IV</subscript>-enriched forest, depending on whether HI lines are associated with C<subscript>IV</subscript> at log N<subscript>CIV</subscript> ≥ 12.2 within a given velocity range. The entire HI column density distribution function (CDDF) can be described as the combination of these two well-characterised populations which overlap at log N<subscript>HI</subscript> ~ 15. At log N<subscript>HI</subscript> ≤ 15, the unenriched forest dominates, showing a similar power-law distribution to the entire forest. The C<subscript>IV</subscript>-enriched forest dominates at log N<subscript>HI</subscript> ≥ 15, with its distribution function as ∝N<subscript>HI</subscript><superscript>~-1.45</superscript>. However, it starts to flatten out at lower N<subscript>HI</subscript>, since the enriched forest fraction decreases with decreasing N<subscript>HI</subscript>. The deviation from the power law at log N<subscript>HI</subscript> = [14,17] shown in the CDDF for the entire HI sample is a result of combining two different HI populations with a different CDDF shape. The total HI mass density relative to the critical density is Ω<subscript>HI</subscript> ~ 1.6 × 10<superscript>-6</superscript> h<superscript>-1</superscript>, where the enriched forest accounts for ~40% of Ω<subscript>HI</subscript>. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00046361
- Volume :
- 552
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Astronomy & Astrophysics / Astronomie et Astrophysique
- Publication Type :
- Academic Journal
- Accession number :
- 89750461
- Full Text :
- https://doi.org/10.1051/0004-6361/201220042