X-ray Insights into the Nature of Weak Emission-Line Quasars at High Redshift - Astrophysics > Astrophysics of GalaxiesReport as inadecuate




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Abstract: We present Chandra observations of nine high-redshift quasars z=2.7-5.9discovered by the Sloan Digital Sky Survey with weak or undetectablehigh-ionization emission lines in their UV spectra WLQs. Adding archivalX-ray observations of six additional sources of this class has enabled us toplace the strongest constraints yet on the X-ray properties of this remarkableclass of AGNs. Although our data cannot rule out the possibility that theemission lines are overwhelmed by a relativistically boosted continuum, asmanifested by BL Lac objects, we find that WLQs are considerably weaker in theX-ray and radio bands than the majority of BL Lacs found at much lowerredshifts. If WLQs are high-redshift BL Lacs, then it is difficult to explainthe lack of a large parent population of X-ray and radio bright weak-linedsources at high redshift. We also consider the possibility that WLQs arequasars with extreme properties, and in particular that the emission lines aresuppressed by high accretion rates. Using joint spectral fitting of the X-rayspectra of 11 WLQs we find that the mean photon index in the hard X-ray band isconsistent with those observed in typical radio-quiet AGNs with no hint of anunusually steep hard-X-ray spectrum. This result poses a challenge to thehypothesis that WLQs have extremely high accretion rates, and we discussadditional observations required to test this idea.



Author: Ohad Shemmer 1,2, W.N. Brandt 1, Scott F. Anderson 3, Aleksandar M. Diamond-Stanic 4, Xiaohui Fan 4, Gordon T. Richards 5, Donald

Source: https://arxiv.org/



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