Spectroscopic Analysis of H I Absorption Line Systems in 40 HIRES Quasars

TL;DR

This study analyzes H I absorption lines in 40 high-resolution quasar spectra, revealing new insights into their properties and distributions near quasars using comprehensive line fitting techniques.

Contribution

It introduces a method using all visible Lyman series lines for more accurate H I line fitting and provides detailed analysis of line properties near quasars.

Findings

Steeper column density distribution for lines near quasars at z < 2.9.

Broader line widths and steeper distributions within 5,000 km/s of quasars.

Identification of components near high column density systems not visible in Lya.

Abstract

We list and analyze H I absorption lines at redshifts 2 < z < 4 with column density (12 < log(N_HI) < 19) in 40 high-resolutional (FWHM = 8.0 km/s) quasar spectra obtained with the Keck+HIRES. We de-blend and fit all H I lines within 1,000 km/s of 86 strong H I lines whose column densities are log(N_HI/[cm^-2]) > 15. Unlike most prior studies, we use not only Lya but also all visible higher Lyman series lines to improve the fitting accuracy. This reveals components near to higher column density systems that can not be seen in Lya. We list the Voigt profile fits to the 1339 H I components that we found. We examined physical properties of H I lines after separating them into several sub-samples according to their velocity separation from the quasars, their redshift, column density and the S/N ratio of the spectrum. We found two interesting trends for lines with 12 < log(N_HI) < 15 which are within 200-1000 km/s of systems with log(N_HI) > 15. First, their column density distribution becomes steeper, meaning relatively fewer high column density lines, at z < 2.9. Second, their column density distribution also becomes steeper and their line width becomes broader by about 2-3 km/s when they are within 5,000 km/s of their quasar.