X-Ray Spectroscopy of Quasi-Stellar Objects with Broad Ultraviolet Absorption Lines

By S. C. Gallagher, W. N. Brandt, G. Chartas, G. Garmire. 2001

161 citations recorded by the source corpus.

For the population of quasi-stellar objects (QSOs) with broad ultraviolet absorption lines, we are just beginning to accumulate X-ray observations with enough counts for spectral analysis at CCD resolution. From a sample of eight QSOs (including four broad absorption line [BAL] QSOs and three mini-BAL QSOs) with ASCA or Chandra spectra with more than 200 counts, general patterns are emerging. Their power-law X-ray continua are typical of normal QSOs with Γ ≈ 2.0, and the signatures of a significant column density [NH ≈ (0.1-4) × 1023 cm-2] of intrinsic, absorbing gas are clear. Correcting the X-ray spectra for intrinsic absorption recovers a normal ultraviolet-to-X-ray flux ratio, indicating that the spectral energy distributions of this population are not inherently anomalous. In addition, a large fraction of our sample shows significant evidence for complexity in the absorption. The subset of BAL QSOs with broad Mg II absorption apparently suffers from Compton-thick absorption completely obscuring the direct continuum in the 2-10 keV X-ray band, complicating any measurement of their intrinsic X-ray spectral shapes.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/498ad605947e2ade351936d92acc00e57164f705

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In Astronomy and Astrophysics

1. D. Schneider
2. W. N. Brandt
3. D. M. Alexander
4. Xiaohui Fan
5. Gordon Richards
6. L. Hernquist
7. Yue Shen
8. P. Hall

Citations in the corpus

• CHANDRA Detects Relativistic Broad Absorption Lines from APM 08279+5255 (2002, methodology): “The present X-ray data for BALQSOs are sparse, and only poor to moderate signal-to-noise ra- tio (S/N) spectra are available (e.g., Chartas et al. 2001; Gallagher et al. 2001; Green et al. 2001; Oshima et al. 2001; Brinkmann et al. 2002; Gallagher et al. 2002).”
• Evidence of a high-velocity ionized outflow in a second narrow-line quasar PG 0844+349 (2003, background): “At X-ray energies most BAL quasars are ‘X-ray weak’, a property explained by line-of-sight absorption in moderately ionized gas with column densities up to N H = 1023 cm−2 (e.g. Hamann 1998; Sabra, & Hamann 2001; Gallagher et al. 2002).”
• X-Ray Emission from Radio-Quiet Quasars in the Sloan Digital Sky Survey Early Data Release: The αox Dependence upon Ultraviolet Luminosity (2002, background): “This effect appears to apply to both low- and high-redshift BALQSOs (e.g., Brandt, Laor, & Wills 2000; Brandt et al. 2001; Vignali et al. 2001a; Gallagher et al. 2002).”
• A CATALOG OF BROAD ABSORPTION LINE QUASARS IN SLOAN DIGITAL SKY SURVEY DATA RELEASE 5 (2008, background): “Compared to typical QSOs of the same UV luminosity, BAL QSOs are unusually X-ray weak (e.g., Green et al. 1995; Brandt et al. 2000) due to strong X-ray absorption (e.g., Green et al. 2001; Gallagher et al. 2001, 2002, and references therein).”
• An Exploratory Chandra Survey of a Well-defined Sample of 35 Large Bright Quasar Survey Broad Absorption Line Quasars (2006, background): “This last quantity was chosen to investigate the possibility that quasars with shallow BALs have lower X-ray absorption column densities, as found for PG 2112+059 (Gallagher et al. 2001) and CSO 755 (Shemmer et al. 2005).”