Quasars with P v broad absorption in BOSS data release 9

Abstract

Broad absorption lines (BALs) found in a significant fraction of quasar spectra identify high-velocity outflows that might be present in all quasars and could be a major factor in feedback to galaxy evolution. Understanding the nature of these flows requires further constraints on their physical properties, including their column densities, for which well-studied BALs, such as C iv λλ1548,1551, typically provide only a lower limit because of saturation effects. Low-abundance lines, such as P v λλ1118,1128, indicate large column densities, implying outflows more powerful than measurements of C iv alone would indicate. We search through a sample of 2694 BAL quasars from the SDSS-III/BOSS DR9 quasar catalog for such absorption, and we identify 81 'definite' and 86 'probable' detections of P v broad absorption, yielding a firm lower limit of 3.0−6.2% for the incidence of such absorption among BAL quasars. The P v-detected quasars tend to have stronger C iv and Si iv absorption, as well as a higher incidence of LoBAL absorption, than the overall BAL quasar population. Many of the P v-detected quasars have C iv troughs that do not reach zero intensity (at velocities where P v is detected), confirming that the outflow gas only partially covers the UV continuum source. P v appears significantly in a composite spectrum of non-P v-detected BAL quasars, indicating that P v absorption (and large column densities) are much more common than indicated by our search results. Our sample of P v detections significantly increases the number of known P v detections, providing opportunities for follow-up studies to better understand BAL outflow energetics.

On the emergence of thousands of absorption lines in the quasar PG 1411+442: a clumpy high-column density outflow from the broad emission-line region?

“…Our finding in PG 1411+442 that the Fe ii and Fe ii* lines require an intense radiation field behind a thick layer of fully-ionised gas suggests that the main parameter driving the progression from HiBALs to LoBALs and FeLoB-ALs is larger total column densities, not smaller ionisation parameters and larger distances from the quasars. This is supported by recent work indicating that BAL outflows typically have large ionisation parameters, log U −0.5, and large column densities in ionised gas, log N H (cm −2 ) 22.7, based on measurements of P v BALs in median composite BAL quasar spectra (Hamann et al 2019, see also Hamann & Ferland 1999;Hamann et al 2002;Leighly et al 2011;Borguet et al 2013;Capellupo et al 2017;Moravec et al 2017). The Hamann et al (2019) study shows further that the stronger low-ionisation lines in LoBALs are accompanied by stronger P v absorption compared to HiBALs.…”

The Sloan Digital Sky Survey Reverberation Mapping Project: Systematic Investigations of Short-timescale C IV Broad Absorption Line Variability

“…We also searched for P vλλ1112,1118 absorption in our significant-variability sample. P v is a lower-abundance ion that has an ionization energy similar to that of C iv, and its presence, like that of Si iv, indicates that the corresponding component of C iv absorption is highly saturated (e.g., Capellupo et al 2017). There have been differing reports on the frequency of P v BALs; Capellupo et al (2017) (2014) report that 88% of their C iv SA troughs show detectable P v, about half of the C iv S0 troughs show detectable P v, and only 12% of C iv 00 troughs are accompanied by P v absorption.…”

“…P v is a lower-abundance ion that has an ionization energy similar to that of C iv, and its presence, like that of Si iv, indicates that the corresponding component of C iv absorption is highly saturated (e.g., Capellupo et al 2017). There have been differing reports on the frequency of P v BALs; Capellupo et al (2017) (2014) report that 88% of their C iv SA troughs show detectable P v, about half of the C iv S0 troughs show detectable P v, and only 12% of C iv 00 troughs are accompanied by P v absorption. The discrepancy in the P v detection percentages between Capellupo et al (2017) andFiliz Ak et al (2014) is likely due to differing identification criteria: Capellupo et al (2013) note that they are extremely conservative in identifying P v and that their algorithm is biased against weaker and narrower features, whereas Filiz Ak et al…”

On the structure and energetics of quasar broad absorption-line outflows

“…The detection rate of P v absorption lines in quasar outflows has not been established due primarily to blending problems in the Lyα forest. Capellupo et al (2017) identified a sample of 167 BAL quasars with definite or probable P v absorption based on visual inspection of spectra in the Baryon Oscillation Spectroscopic Survey (BOSS, Dawson et al 2013;Pâris et al 2017) of the Sloan Digital Sky Survey III (SDSS-III, Eisenstein et al 2011). Some of the quasars in that study have clearly-resolved P v doublets troughs that reveal ∼1:1 depth ratios, such that the P v itself is saturated and the total outflow column densities could be much larger than the lower limit mentioned above.…”