Abstract
We study the X-ray spectral evolution of quasars with red-shift using a sample of 1280 quasars constructed by cross-referencing the XMM-Newton 3XMM−DR7 and the optical SDSS-DR14 catalogues. The sources were selected to have a minimum detected X-ray counts >600 and which were not affected by high background. The sample redshift distribution ranges from 0-4.9 and peaks around 1. For each source, the XMM-Newton EPIC_PN spectra were generated and fitted with a power-law model with Galactic absorption. Consistent with some earlier results we find a strong correlation between the photon index and redshift. We explicitly test the hypothesis that this is due to the X-ray soft excess and reflection bump being red-shifted away from the XMM band, by adding a black body and reflection component and find that the correlation is no longer significant. Thus, for the first time, we show that there is no evidence for quasar spectral evolution and the correlation between index and red-shift is indeed due to the soft excess and reflection component.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
