The extremely X-ray luminous radio-loud quasar CFHQS J142952+544717 at z=6.18 under Chandra high-angular resolution lens

We present the first X-ray observation at sub-arcsecond resolution of the high-redshift (z = 6.18) radio-loud quasar CFHQS J142952 + 544717 (J1429). The similar to 100 net-count 0.3-7 keV spectrum obtained from similar to 30 ks Chandra exposure is best fit by a single power-law model with a photon index Gamma = 2.0 +/- 0.2 and no indication of an intrinsic absorber, implying a 3.6-72 keV rest-frame luminosity L X = (2.3(-0.5)(+0.6)) x 10(46) erg s(-1). We identify a second X-ray source at 30 '' distance from J1429 position, with a soft (Gamma similar or equal to 2.8) and absorbed (equivalent hydrogen column density N-H < 13.4 x 10(20) cm(-2)) spectrum, which likely contaminated J1429 spectra obtained in lower angular resolution observations. Based on the analysis of the Chandra image, the bulk of the X-ray luminosity is produced within the central similar to 3 kpc region, either by the disc/corona system, or by a moderately aligned jet. In this context, we discuss the source properties in comparison with samples of low- and high-redshift quasars. We find indication of a possible excess of counts over the expectations for a point-like source in a 0.5 ''-1.5 '' (similar to 3-8 kpc) annular region. The corresponding X-ray luminosity at J1429 redshift is 4 x 10(45) erg s(-1). If confirmed, this emission could be related to either a large-scale X-ray jet, or a separate X-ray source.