THE DEPENDENCE OF C IV BROAD ABSORPTION LINE PROPERTIES ON ACCOMPANYING Si IV AND Al III ABSORPTION: RELATING QUASAR-WIND IONIZATION LEVELS, KINEMATICS, AND COLUMN DENSITIES

Abstract

We consider how the profile and multi-year variability properties of a large sample of C iv Broad Absorption Line (BAL) troughs change when BALs from Si iv and/or Al iii are present at corresponding velocities, indicating that the line-of-sight intercepts at least some lower ionization gas. We derive a number of observational results for C iv BALs separated according to the presence or absence of accompanying lower ionization transitions, including measurements of composite profile shapes, equivalent width (EW), characteristic velocities, composite variation profiles, and EW variability. We also measure the correlations between EW and fractional-EW variability for C iv, Si iv, and Al iii. Our measurements reveal the basic correlated changes between ionization level, kinematics, and column density expected in accretion-disk wind models; e.g., lines-of-sight including lower ionization material generally show deeper and broader C iv troughs that have smaller minimum velocities and that are less variable. Many C iv BALs with no accompanying Si iv or Al iii BALs may have only mild or no saturation.

Rapid BAL Variability: Re-Emerging Absorption

“…Time dependent EW variability of BAL troughs is largely investigated at the timescales of years (e.g., Barlow et al, 1992;Lundgren et al, 2007;Capellupo et al, 2012;Filiz Ak et al, 2012, 2014. So far, however, only a small number of disappearance events are recorded (Filiz Ak et al, 2012;McGraw et al, 2017).…”

“…SDSS BOSS carried out spectroscopic observations of 297301 quasars using a 2.5 m dedicated telescope at Apache Point Observatory (Gunn et al, 2006) between 2009and 2014(Eisenstein et al, 2011Dawson et al, 2013). The main aim of BOSS is to map the spatial distribution of luminous red galaxies and quasars to detect the characteristic scale imprinted by baryon acoustic oscillations in the early universe.…”

“…BAL troughs observed in quasar spectra present characteristic variations in their equivalent widths (EW), line profiles, and velocities (Barlow et al, 1992;Lundgren et al, 2007;Filiz Ak et al, 2012, 2014. The timescales of significant variations ranges between a few years to a few tens of hours (Capellupo et al, 2012;Filiz Ak et al, 2012, 2014Grier et al, 2015).…”

“…The timescales of significant variations ranges between a few years to a few tens of hours (Capellupo et al, 2012;Filiz Ak et al, 2012, 2014Grier et al, 2015).…”

“…One scenario involves transverse motion of absorbing gas across the observer's line of sight producing changes in the coverage fraction (e.g., Rogerson et al, 2016). A second scenario considers ionization level changes of the outflowing gas (e.g., Filiz Ak et al, 2013Ak et al, , 2014. Other scenarios (e.g., intrinsic instabilities of an absorbing gas driving BAL variations) are usually found potential but problematic (Capellupo et al, 2012).…”