X- Ray Insights into the Nature of Quasars with Redshifted Broad Absorption Lines

ZHANG N., Brandt W. N., AHMED N. S., Hall P. B., LUO B., Anderson S. F., ...More

ASTROPHYSICAL JOURNAL, vol.839, no.2, 2017 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 839 Issue: 2
  • Publication Date: 2017
  • Doi Number: 10.3847/1538-4357/aa6842
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: accretion, accretion disks, galaxies: nuclei, quasars: absorption lines, quasars: general, X-rays: galaxies, DIGITAL SKY SURVEY, SPECTRAL ENERGY-DISTRIBUTIONS, SUPERMASSIVE BLACK-HOLE, ACTIVE GALACTIC NUCLEI, DRIVEN DISK WINDS, PHL 1811 ANALOGS, EMISSION-LINE, UV PROPERTIES, AGN FEEDBACK, RADIO
  • Erciyes University Affiliated: Yes


We present Chandra observations of seven broad absorption line (BAL) quasars at z = 0.863-2.516 with redshifted BAL troughs (RSBALs). Five of our seven targets were detected by Chandra in 4-13 ks exposures with ACIS-S. The alpha(ox) values, Delta alpha(ox) values, and spectral energy distributions of our targets demonstrate they are all X-ray weak relative to expectations for non-BAL quasars, and the degree of X-ray weakness is consistent with that of appropriately matched BAL quasars generally. Furthermore, our five detected targets show evidence for hard X-ray spectral shapes with a stacked effective power-law photon index of Gamma(eff) = 0.5(-0.4)(+0.5). These findings support the presence of heavy X-ray absorption (N-H approximate to 2 x 10(23) cm(-2)) in RSBAL quasars, likely by the shielding gas found to be common in BAL quasars more generally. We use these X-ray measurements to assess models for the nature of RSBAL quasars, finding that a rotationally dominated outflow model is favored while an infall model also remains plausible with some stipulations. The X-ray data disfavor a binary quasar model for RSBAL quasars in general.