Chandra X-Ray Imaging and an Inverse Compton/Cosmic Microwave Background Model for the Inner Jet of PKS 0637–752

Abstract

We present the X-ray surface brightness maps of the jet from the quasar PKS 0637−752, using two epochs of archival Chandra observations (1999 and 2017). We present, for the first time, a model of the faint inner jet extending from 3 .″ 4 to 7″ from the core, interpreting its X-ray emission as inverse Compton (CMB) scattering of cosmic microwave background photons by the synchrotron-emitting relativistic electrons. The inner jet contrasts with the bright outer part of the jet, dominated by several discrete knots for which upper limits to the Fermi gamma-ray flux rule out the CMB mechanism. It is the first detailed CMB model published for this inner jet. We examine three physically motivated scenarios, distinguished by the high-energy cutoff of the electron distribution, that can account for the observed radio, millimeter/submillimeter, and X-ray emission while remaining consistent with optical and gamma-ray upper limits. We also report for the first time X-rays from the radio lobe at the end of the receding jet.