The Proximity Effect, the UV Background, and the Statistics of the LY alpha Lines at High Resolution

Open Access
Publisher Website
Google Scholar
Abstract
We present results from high resolution (Rsimeq 28000) spectra of six high- redshift QSOs taken at the ESO NTT telescope that allow the detailed study of the Ly-alpha population in the redshift interval z=2.8-4.1. The typical Doppler parameters found for the Ly-alpha lines lie in the interval b=20div30 km/s, corresponding to temperatures T>24000K, with a fraction of the order 15% in the range 10=13.3) in the redshift interval z=1.7-4.1. A Maximum Likelihood analysis has been applied to estimate SIMULTANEOUSLY the best fit parameters of the Ly-alpha$ statistics AND of the UV background. After correcting for the blanketing of weak lines, we confirm that the column density distribution is best represented by a double power-law with a break at logN_{HI}simeq14, with a slope beta_s=1.8 for higher column densities and a flatter slope beta_f=1.4 below the break. A value J_{LL}= 5 pm1 imes10^{-22} erg/cm^2/s/Hz/sr is derived for the UV background in the redshift interval z=1.7-4.1, consistent with the predicted QSO contribution. No evidence is found for redshift evolution of the UVB in the same redshift interval. The comoving volume density distributions of protogalactic Damped and Lyman Lymit systems and Ly-alpha clouds with log N_{HI}>= 14 and radii Rsimeq 200 kpc are found to be similar, suggesting a possible common association with galaxies.Comment: 24 pages (2 macros included) + 9 figures. Accepted for publication on ApJ. Revised version: minor changes to text and fig 8 and

This publication has 0 references indexed in Scilit: