DISCOVERY OF A z = 4.93, X-RAY-SELECTED QUASAR BY THE CHANDRA MULTIWAVELENGTH PROJECT (ChaMP)

摘要

We present X-ray and optical observations of CXOMP J213945.0-234655, a high-redshift (z = 4.93) quasar discovered through the Chandra Multiwavelength Project (ChaMP). This object is the most distant X-ray-selected quasar published, with a rest-frame X-ray luminosity of L_X = 5.9 x 10~(44) ergs s~(-1) (measured in the 0.3-2.5 keV band and corrected for Galactic absorption). CXOMP J213945.0-234655 is a g′ dropout object (>26.2), with r′ = 22.87 and i′ = 21.36. The rest-frame X-ray-to-optical flux ratio is similar to quasars at lower redshifts and slightly X-ray bright relative to z > 4 optically selected quasars observed with Chandra. The ChaMP is beginning to acquire significant numbers of high-redshift quasars to investigate the X-ray luminosity function out to z ～ 5.