Narrow C IV absorption doublets on quasar spectra of the Baryon Oscillation Spectroscopic Survey

TL;DR

This study systematically surveys narrow C IV absorption lines in quasar spectra from the BOSS survey, revealing their properties, evolution, and dependence on quasar luminosity, extending previous work to include absorbers near the emission line.

Contribution

It extends prior surveys to include C IV NALs near the quasar emission line, providing a comprehensive catalog and analysis of their properties and evolution.

Findings

Stronger C IV NALs tend to be saturated.

Associated systems have larger absorption strengths than intervening ones.

Redshift density evolution of absorbers mirrors cosmic star formation history.

Abstract

In this paper, we extend our works of Papers I and II, which are assigned to systematically survey \CIVab\ narrow absorption lines (NALs) with \zabs$\ll$\zem\ on quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS), to collect \CIV\ NALs with \zabs$\approx$\zem\ from blue to red wings of \CIVwave\ emission lines. Together with Papers I and II, we have collected a total number of 41,479 \CIV\ NALs with $1.4544\le$\zabs$\le4.9224$ in surveyed spectral region redward of \lya\ until red wing of \CIVwave\ emission line. We find that the stronger \CIV\ NALs tend to be the more saturated absorptions, and associated systems (\zabs$\approx$\zem) seem to have larger absorption strengths when compared to intervening ones (\zabs$\ll$\zem). The redshift density evolution behavior of absorbers (the number of absorbers per redshift path) is similar to the history of the cosmic star formation. When compared to the quasar-frame velocity ($\beta$) distribution of \MgII\ absorbers, the $\beta$ distribution of \CIV\ absorbers is broader at $\beta\approx0$, shows longer extended tail, and exhibits a larger dispersion for environmental absorptions. In addition, for associated \CIV\ absorbers, we find that low-luminosity quasars seem to exhibit smaller $\beta$ and stronger absorptions when compared to high-luminosity quasars.