X-Ray Emission from Radio-Quiet Quasars in the Sloan Digital Sky Survey Early Data Release: The αox Dependence upon Ultraviolet Luminosity

By C. Vignali, W. N. Brandt, D. Schneider. 2002

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We investigate the X-ray properties of the color-selected, radio-quiet quasars (RQQs) in the Sloan Digital Sky Survey (SDSS) Early Data Release using ROSAT, Chandra, and XMM-Newton data. In the 0.16–6.28 redshift range, 136 RQQs have X-ray detections (69 from the ROSAT All-Sky Survey, RASS), while for 70 RQQs X-ray upper limits are obtained. The well-defined selection method used by the SDSS, coupled with the tight radio constraints from the FIRST and NVSS surveys, allows us to define a representative sample of optically selected RQQs whose broadband spectral energy distributions (characterized by means of the optical–to–X-ray spectral index, αox) can be studied as a function of rest-frame ultraviolet (UV) luminosity and redshift. A partial correlation analysis applied to the SDSS sample (including the upper limits, but excluding the biased subsample of RASS detections) shows that αox is a function of rest-frame UV luminosity (i.e., αox steepens at high UV luminosities); this correlation is significant at the 3.7 σ level. We do not detect a highly significant redshift dependence of αox. We also find a significant (7.8 σ level) correlation between UV and X-ray luminosity. This correlation, parameterized by LX ∝ L, extends previous results to the highest redshifts.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/636fa808201fe90a42acec9971dd1e3594b3af5e

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Citations in the corpus

The X-Ray-to-Optical Properties of Optically Selected Active Galaxies over Wide Luminosity and Redshift Ranges (2006, background): “…luminosity (erg s−1 Hz−1) at frequencyν in the rest-frame, has been the subject of many studies over the last two decades (e.g., Avni & Tananbaum 1982; Kriss & Canizares 1985; Avni & Tananbaum 1986; Anderson & Margon 1987; Wilkes et al. 1994; Vignali et al. 2003; Strateva et al. 2005).”
The Relation between Quasar and Merging Galaxy Luminosity Functions and the Merger-driven Star Formation History of the Universe (2006, methodology): “This includes the observed dependence of the optical–to–X-ray luminosity ratio on luminosity (e.g., Wilkes et al. 1994; Green et al. 1995; Vignali et al. 2003; Risaliti & Elvis 2005; Strateva et al. 2005), but for our purposes adopting the mean observed quasar SED from Richards et al. (2006b)…”
The bolometric quasar luminosity function at z = 0–7 (2020, background): “These investigations of the QLF have also found that both the typical spectral shape (e.g., Wilkes et al. 1994; Green et al. 1995; Vignali et al. 2003; Strateva et al. 2005; Richards et al. 2006b; Steffen et al. 2006; Just et al. 2007; Lusso et al. 2010; Kashikawa et al. 2015; Lusso & Risaliti…”
Black Hole Growth to z = 2 - I: Improved Virial Methods for Measuring M_BH and L/L_Edd (2012, background): “This dependence is most significant at the X-ray regime, and perhaps also at UV wavelengths (e.g., Vignali et al. 2003).”