The X-ray properties of the most luminous quasars from the sloan digital sky survey

D. W. Just, W. N. Brandt, O. Shemmer, A. T. Steffen, D. P. Schneider, G. Chartas, G. P. Garmire

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295 Scopus citations


Utilizing 21 new Chandra observations as well as archival Chandra, ROSAT, and XMM-Newton data, we study the X-ray properties of a representative sample of 59 of the most optically luminous quasars in the universe (Mi = -29.3 to -30.2) spanning a redshift range of z =1.5-4.5. Our full sample consists of 32 quasars from the Sloan Digital Sky Survey (SDSS) Data Release 3 (DR3) quasar catalog, two additional objects in the DR3 area that were missed by the SDSS selection criteria, and 25 comparably luminous quasars at z ≥ 4. This is the largest X-ray study of such luminous quasars to date. By jointly fitting the X-ray spectra of our sample quasars, excluding radio-loud and broad absorption line (BAL) objects, we find a mean X-ray power-law photon index of Γ = 1.92+0.09/-0.08 constrain any neutral intrinsic absorbing material to have a mean column density of NH≤ 2 × 1021 cm-2. We find, consistent with other studies, that Γ does not change with redshift, and we constrain the amount of allowed T evolution for the most luminous quasars. Our sample, excluding radio-loud and BAL quasars, has a mean X-ray-to-optical spectral slope of αox = -1.80 ± 0.02, as well as no significant evolution of αox with redshift. We also comment on the X-ray properties of a number of notable quasars, including an X-ray-weak quasar with several strong narrow absorption line systems, a mildly radio-loud BAL quasar, and a well-studied gravitationally lensed quasar.

Original languageEnglish (US)
Pages (from-to)1004-1022
Number of pages19
JournalAstrophysical Journal
Issue number2 I
StatePublished - Aug 10 2007

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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