Voigt-profile analysis of the Ly alpha forest in a cold dark matter universe

被引:110
作者
Dave, R
Hernquist, L
Weinberg, DH
Katz, N
机构
[1] OHIO STATE UNIV,DEPT ASTRON,COLUMBUS,OH 43210
[2] UNIV WASHINGTON,DEPT ASTRON,SEATTLE,WA 98195
关键词
galaxies; formation; large-scale structure of universe; line; profiles; methods; numerical; quasars; absorption lines;
D O I
10.1086/303712
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We use an automated Voigt-profile fitting procedure to extract statistical properties of the Ly alpha forest in a numerical simulation of an Omega = 1, cold dark matter (CDM) universe. Our analysis method is similar to that used in most observational studies of the forest, and we compare the simulations to recently published results derived from Keck HIRES spectra. With the Voigt-profile decomposition analysis, the simulation reproduces the large number of weak lines (N-HI less than or similar to 10(14) cm(-2)) found in the HIRES spectra. The column density distribution evolves significantly between z = 3 and z = 2, with the number of lines at fixed column density dropping by a factor similar to 1.6 in the range where line blending is not severe. At z = 3, the b-parameter distribution has a median of 35 km s(-1) and a dispersion of 20 km s(-1), in reasonable agreement with the observed values. The comparison between our new analysis and recent data strengthens earlier claims that the Ly alpha forest arises naturally in hierarchical structure formation as photoionized gas falls into dark matter potential wells. However, there are two statistically significant discrepancies between the simulated forest and the HIRES results: the model produces too many lines at z = 3 by a factor similar to 1.5-2, and it produces more narrow lines (b < 20 km s(-1)) than are seen in the data. The first result is sensitive to our adopted normalization of the mean Ly alpha optical depth, and the second is sensitive to our assumption that helium reionization has not significantly raised gas temperatures at z = 3. It is therefore too early to say whether these discrepancies indicate a fundamental problem with the high-redshift structure of the Omega = 1 CDM model or reflect errors of detail in our modeling of the gas distribution or the observational procedures.
引用
收藏
页码:21 / 26
页数:6
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