Volume 451, Number 3, June I 2006
|Page(s)||767 - 776|
|Section||Cosmology (including clusters of galaxies)|
|Published online||04 May 2006|
Simulations of thermally broadened H I Ly α absorption arising in the warm-hot intergalactic medium
Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: email@example.com
2 Department of Astronomy, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720, USA
3 Department of Physics, University of Oxford, Keble Road, Oxford OX13RH, UK
Accepted: 8 February 2006
Recent far-ultraviolet (FUV) absorption line measurements of low-redshift quasars have unveiled a population of intervening broad H i Ly α absorbers (BLAs) with large Doppler parameters ( km s-1). If the large width of these lines is dominated by thermal line broadening, the BLAs may trace highly-ionized gas in the warm-hot intergalactic medium (WHIM) in the temperature range K, a gas phase that is expected to contain a large fraction of the baryons at low redshift. In this paper we use a hydrodynamical simulation to study frequency, distribution, physical conditions, and baryon content of the BLAs at . From our simulated spectra we derive a number of BLAs per unit redshift of for H i absorbers with log (cm(km s, km s-1, and total hydrogen column densities N(H ii cm-2. The baryon content of these systems is , which represents ∼25 percent of the total baryon budget in our simulation. Our results thus support the idea that BLAs represent a significant baryon reservoir at low redshift. BLAs predominantly trace shock-heated collisionally ionized WHIM gas at temperatures log . About 27 percent of the BLAs in our simulation originate in the photoionized Ly α forest (log ) and their large line widths are determined by non-thermal broadening effects such as unresolved velocity structure and macroscopic turbulence. Our simulation implies that for a large-enough sample of BLAs in FUV spectra it is possible to obtain a reasonable approximation of the baryon content of these systems solely from the measured H i column densities and b values.
Key words: methods: numerical / cosmology: miscellaneous / large-scale structure of Universe
© ESO, 2006
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.