CIV Emission and the ultraviolet through X-ray spectral energy distribution of radio-quiet quasars

Nicholas E. Kruczek*, Gordon T. Richards, S. C. Gallagher, Rajesh P. Deo, Patrick B. Hall, Paul C. Hewett, Karen M. Leighly, Coleman M. Krawczyk, Daniel Proga

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


In the rest-frame ultraviolet (UV), two of the parameters that best characterize the range of emission-line properties in quasar broad emission-line regions are the equivalent width and the blueshift of the C IV λ1549 line relative to the quasar rest frame. We explore the connection between these emission-line properties and the UV through X-ray spectral energy distribution (SED) for radio-quiet (RQ) quasars. Our sample consists of a heterogeneous compilation of 406 quasars from the Sloan Digital Sky Survey (at z > 1.54) and Palomar-Green survey (at z < 0.4) that have well-measured C IV emission-line and X-ray properties (including 164 objects with measured Γ). We find that RQ quasars with both strong C IV emission and small C IV blueshifts can be classified as "hard-spectrum" sources that are (relatively) strong in the X-ray as compared to the UV. On the other hand, RQ quasars with both weak C IV emission and large C IV blueshifts are instead "soft-spectrum" sources that are (relatively) weak in the X-ray as compared to the UV. This work helps to further bridge optical/soft X-ray "eigenvector 1" relationships to the UV and hard X-ray. Based on these findings, we argue that future work should consider systematic errors in bolometric corrections (and thus accretion rates) that are derived from a single mean SED. Detailed analysis of the C IV emission line may allow for SED-dependent corrections to these quantities.

Original languageEnglish
Article number130
Number of pages12
JournalAstronomical Journal
Issue number4
Early online date15 Sept 2011
Publication statusPublished - 1 Oct 2011


  • accretion, accretion disks
  • line: profiles
  • quasars: emission lines
  • quasars: general
  • ultraviolet: galaxies
  • X-rays: galaxies


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