Redshift-evolutionary X-ray and UV luminosity relation of quasars from Gaussian copula
Abstract
We construct a three-dimensional and redshift-evolutionary X-ray and ultraviolet (LX-LUV) luminosity relation for quasars from the powerful statistic tool called copula, and find that the constructed LX-LUV relation from copula is more viable than the standard one and the observations favor the redshift-evolutionary relation more than 3σ. The Akaike and Bayes information criterions indicate that the quasar data support strongly the three-dimensional LX-LUV relation. Our results show that the quasars can be regarded as a reliable indicator of the cosmic distance if the LX-LUV relation from copula is used to calibrate quasar data.
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