X-ray and optical properties of Broad Absorption Line Quasars in the Canada-France-Hawaii Telescope Legacy SurveyReportar como inadecuado



 X-ray and optical properties of Broad Absorption Line Quasars in the Canada-France-Hawaii Telescope Legacy Survey


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We study the X-ray and optical properties of 16 Broad Absorption Line BAL quasars detected in about 3 degree square region common to the wide synoptic W-1 component of the Canada-France-HawaiiTelescope Legacy Survey CFHTLS and the XMM Large Scale Structure survey XMM-LSS. The BAL fraction is found to be 10% in full sample, 7% for the optical colour selected QSOs and as high as 33% if we consider QSOs selected from their IR colours. The X-ray detected non-BAL and BAL quasars have a mean observed X-ray-to-optical spectral slope of -1.47 +- 0.13 and -1.66 +- 0.17 respectively. We also find that the BAL QSOs have alpha ox systematically smaller than what is expected from the relationship between optical luminosity and alpha ox as derived from our sample. Based on this, we show, as already reported in the literature for quasars with high optical luminosities, our new sample of BAL QSOs have X-ray luminosity a factor of three smaller than what has been found for non-BAL QSOs with similar optical luminosities. Comparison of hardness ratio of the BAL and non-BAL QSOs suggests a possible soft X-ray weakness of BAL QSOs. Combining our sample, of relatively fainter QSOs, with others from the literature we show that larger balnicity index BI and maximum velocity V max of the C IV absorption are correlated with steeper X-ray to optical spectral index. We argue that this is most likely a consequence of the existence of a lower envelope in the distribution of BI or V max values versus optical luminosity. Our results thus show that the previously known X-ray weakness of BAL QSOs extends to lower optical luminosities as well.



Autor: C. S. Stalin; R. Srianand; P. Petitjean

Fuente: https://archive.org/







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