A Census of Intrinsic Narrow Absorption Lines in the Spectra of Quasars at z = 2–4

Abstract

We use Keck/HIRES spectra of 37 optically bright quasars at z = 2-4 to study narrow absorption lines that are intrinsic to the quasars (intrinsic NALs, produced in gas that is physically associated with the quasar central engine). We identify 150 NAL systems, that contain 124 C IV, 12 N V, and 50 Si IV doublets, of which 18 are associated systems (within 5,000 km s −1 of the quasar redshift). We use partial coverage analysis to separate intrinsic NALs from NALs produced in cosmologically intervening structures. We find 39 candidate intrinsic systems, (28 reliable determinations and 11 that are possibly intrinsic). We estimate that 10-17% of C IV systems at blueshifts of 5,000-70,000 km s −1 relative to quasars are intrinsic. At least 32% of quasars contain one or more intrinsic C IV NALs. Considering N V and Si IV doublets showing partial coverage as well, at least 50% of quasars host intrinsic NALs. This result constrains the solid angle subtended by the absorbers to the background source(s). We identify two families of intrinsic NAL systems, those with strong N V absorption, and those with negligible absorption in N V, but with partial coverage in the C IV doublet. We discuss the idea that these two families represent different regions or conditions in accretion disk winds. Of the 26 intrinsic C IV NAL systems, 13 have detectable low-ionization absorption lines at similar velocities, suggesting that these are two-phase structures in the wind rather than absorbers in the host galaxy. We also compare possible models for quasar outflows, including radiatively accelerated disk-driven winds, magnetocentrifugally accelerated winds, and pressure-driven winds, and we discuss ways of distinguishing between these models observationally.

Multiwavelength campaign on Mrk 509

“…When UV absorption lines are detected in low-redshift AGN, they are generally blue shifted Dunn et al 2007). This is also true of higher redshift quasars (Weymann et al 1979;Ganguly et al 2001;Misawa et al 2007), although Weymann et al (1979) did suggest that systems with red-shifted absorption lines could be associated with neighboring galaxies in clusters. However, given the significant blue shifts of the UV emission lines often used to define the quasar redshift, such redshifted systems could well be blueshifted relative to the systemic velocities of the host galaxies.…”

HS 1700+6416: the first high-redshift unlensed narrow absorption line-QSO showing variable high-velocity outflows

“…and Si IV absorption lines in the SDSS spectrum, that are blue-shifted at mildly (∼2.4 × 10 4 km s −1 ) relativistic velocities (Misawa et al 2007). The source has a very faint ROSAT counterpart (Reimers et al 1995).…”

A HOT GASEOUS GALAXY HALO CANDIDATE WITH Mg X ABSORPTION

“…Some AGNs can have very high velocity outflows (up to ∼ 0.2 c), while the velocity widths can be quite narrow (∼ 100 km s −1 ), which may be mistaken as intervening absorption systems (Misawa et al 2007). These high velocity outflows sometimes can be distinguished from intervening systems, if they show absorption line variability, partial covering, or a density sensitive line from excited states (Teng et al 2013;Muzahid et al 2013;Finn et al 2014;Muzahid et al 2016b).…”