The X-Ray Properties of the Most Luminous Quasars from the Sloan Digital Sky Survey

By D. Just, W. N. Brandt, O. Shemmer, A. Steffen, D. Schneider, G. Chartas, G. Garmire. 2007

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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 and 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 Γ 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.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/dc981b204a5b9deb1c5f1135dfc4f5a5dec47f63

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Citations in the corpus

x-cigale: fitting AGN/galaxy SEDs from X-ray to infrared (2020, methodology): “7 http://cxc.harvard.edu/toolkit/pimms.jsp MNRAS 000, 1–18 (2018) Table 2.”
A HUBBLE DIAGRAM FOR QUASARS (2015, methodology): “…z Llog UV Llog X Reference (erg s−1 Hz−1) (erg s−1 Hz−1) 222 0.061–6.280 28.94–32.90 25.14–28.09 Steffen et al. (2006) 20 1.760–4.610 32.14–32.85 27.14–28.07 Just et al. (2007) 14 4.720–6.220 31.38–32.42 26.62–27.62 Shemmer et al. (2006) 327 0.345–4.255 28.96–31.79 25.08–27.14 Lusso et al. (2010)…”
The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei (2008, methodology): “…has been reported in numerous studies (e.g., Nandra & Pounds 1994, Reeves & Turner 2000; Page et al. 2005; Shemmer et al. 2005; Vignali et al. 2005; Just et al. 2007), and typically no strong dependence ofΓ n redshift or luminosity has been detected across the widest possible ranges of these…”
A CATALOG OF BROAD ABSORPTION LINE QUASARS IN SLOAN DIGITAL SKY SURVEY DATA RELEASE 5 (2008, background): “Recent studies have carefully quantified the UV/X-ray luminosity relation across ≈ 5 orders of magnitude in UV luminosity (e.g., Strateva et al. 2005; Steffen et al. 2006; Just et al. 2007).”
The bolometric quasar luminosity function at z = 0–7 (2020, background): “For example, Steffen et al. (2006) measured β = 0.721 ± 0.011 and C = 4.531 ± 0.688; Just et al. (2007) measured β = 0.709 ± 0.010 and C = 4.822 ± 0.627; Lusso et al. (2010) measured β = 0.760± 0.022 and C = 3.508± 0.641.”
On the origin of radio emission in radio-quiet quasars (2008, background): “More specifically, Just et al. (2007) find that L2 keV ∝ L0.”
THE SIMULTANEOUS OPTICAL-TO-X-RAY SPECTRAL ENERGY DISTRIBUTION OF SOFT X-RAY SELECTED ACTIVE GALACTIC NUCLEI OBSERVED BY SWIFT (2010, background): “Also our sample shows the well-known relation found by e.g. Yuan et al. (1998); Strateva et al. (2005); Just et al. (2007); Gibson et al. (2008) that AGN with higher luminosity density at 2500Å appear to be X-ray weaker at 2 keV.”
Observational evidence for intermediate-mass black holes (2017, background): “…sample studied in X-rays by Baldassare et al. (2017), the X-ray observations show that most of the low-mass AGN have X-ray to UV ratios (αOX) below the correlation between αOX and luminosity density at 2500 Å (l2500) defined for more luminous sources hosting SMBHs (Just et al. 2007; see Fig.”
Cosmic X-ray surveys of distant active galaxies (2015, methodology): “Most recent studies of X-ray-to-optical/UV SEDs using αox find no significant evolution with redshift (e.g., Steffen et al 2006; Just et al 2007; Green et al 2009; Lusso et al 2010); the tightest limits require the X-ray-to-optical/UV luminosity ratio to change by <∼ 30% out to z = 5–6.”
The X-ray to optical-UV luminosity ratio of X-ray selected type 1 AGN in XMM-COSMOS (2009, background): “L2500Å vs L2 keV Previous studies on optically selected AGN reported a relationship between L2 keV and L2500 Å in the form L2 keV ∝ L β 2500 Å , with the best-fit values of the exponent between 0.7 ÷ 0.8 (e.g. Avni & Tananbaum 1982, 1986; Chanan 1983; Kriss & Canizares 1985; Anderson & Margon 1987; ”
Erratum: Updating quasar bolometric luminosity corrections (2012, background): “We might expect that a higher order bolometric correction may fit the data due to the relationship between optical-Xray slope, αox, and luminosity (e.g., Just et al. 2007).”
UNIFICATION OF LUMINOUS TYPE 1 QUASARS THROUGH C iv EMISSION (2010, background): “Specifically, there is a nonlinear scaling of 2 keV X-ray luminosity with the UV luminosity at 2500 Å (e.g., Avni & Tananbaum 1982; Green et al. 1995; Steffen et al. 2006; Just et al. 2007).”
Bolometric luminosities and Eddington ratios of X-ray selected active galactic nuclei in the XMM-COSMOS survey (2012, background): “…asαox = −Log [L2 keV/L2500 Å]/2.605, and the optical luminosity (Tananbaum et al. 1979; Zamorani et al. 1981; Vignali et al. 2003; Steffen et al. 2006; Just et al. 2007; Young et al. 2009; Lusso et al. 2010; Marchese et al. 2012), or betweenαox and the Eddington ratio (Vasudevan & Fabian 2007;…”
CAIXA: a catalogue of AGN in the XMM-Newton archive - II. Multiwavelength correlations (2009, background): “The increasing optical-to-X-ray ratio with increasing optical luminosity is a well established result in AGN research (see e.g. Avni & Tananbaum 1986; Just et al. 2007, and references therein).”