📝 SummarXiv

Abstract

We perform milliarcsecond X-ray astrometry of the quadruply lensed radio-quiet quasar GraL J065904.1+162909 (J0659). This z = 3.083 quasar is lensed into four images and was discovered with the second Data Release of the Gaia Space Observatory (Gaia DR2). The methodology of using gravitational lenses as high resolution telescopes has been applied, so far, to five lensed quasars (including J0659) and shows potential to elucidate the spatial origin of the X-ray and optical emitting regions in distant quasars. We use Gaia DR3 and HST observations of J0659 and infer a mass model for the deflector that reproduces the positions of the quasar lensed images to milliarcsecond precision. Next, we apply archival Chandra observations of J0659, together with our lens model, to conduct a Bayesian test evaluating whether the X-ray emitting region coincides with the optical source position predicted by our mass model. We constrain the origin of the X-ray emission to be within a 0.''030 x 0.''020 ellipse at the 99.7% level, finding the maximum possible distance between the X-ray and optical source is 44.7 milliarcseconds. Our methodology enhances Chandra's spatial resolution at high-z by a factor of 6. We provide a novel approach that extends the methodology towards investigating the origin of the soft and hard X-ray emitting regions in lensed quasars. We elaborate on the potential of upcoming broadband and spectrally resolved X-ray astrometric studies to probe complex quasar morphology at high-z and to identify dual and binary AGN candidates.