Narrow CIV absorption doublets on quasar spectra of the Baryon Oscillation Spectroscopic Survey.

In this paper, we extend our work of Papers I and II, which are assigned to systematically survey C IV λλ 1548,1551 narrow absorption lines (NALs) with z_abs << z_em on quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS) to collect C IV NALs with z_abs ≈ z_em from blue to red wings of C IV λ 1549 emission lines. Together with Papers I and II, we have collected a total number of 41 479 C IV NALs with 1.4544 ≤ z_abs ≤ 4.9224 in surveyed spectral region redward of Lyα until red wing of CIV λ 1549 emission line. We find that the stronger C IV NALs tend to be the more saturated absorptions, and associated systems (z_abs ≈ z_em) seem to have larger absorption strengths when compared to intervening ones (z_abs << z_em). The redshift density evolution behaviour 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 (β) distribution of Mg n absorbers, the β distribution of C IV absorbers is broader at β ≈ 0, shows longer extended tail, and exhibits a larger dispersion for environmental absorptions. In addition, for associated C IV absorbers, we find that low-luminosity quasars seem to exhibit smaller β and stronger absorptions when compared to high-luminosity quasars. [ABSTRACT FROM AUTHOR]