Abstract
The quasar PKS 0637-752, the first celestial X-ray target of the Chandra X-Ray Observatory, has revealed asymmetric X-ray structure extending from 3'' to 12'' west of the quasar, coincident with the inner portion of the jet previously detected in a 4.8 GHz radio image (Tingay et al. 1998). At a redshift of z = 0.651, the jet is the largest (100 kpc in the plane of the sky) and most luminous (~1044.6 ergs s-1) of the few so far detected in X-rays. This Letter presents a high-resolution X-ray image of the jet, from 42 ks of data when PKS 0637-752 was on-axis and ACIS-S was near the optimum focus. For the inner portion of the radio jet, the X-ray morphology closely matches that of new Australian Telescope Compact Array radio images at 4.8 and 8.6 GHz. Observations of the parsec-scale core using the very long baseline interferometry space observatory program mission show structure aligned with the X-ray jet, placing important constraints on the X-ray source models. Hubble Space Telescope images show that there are three small knots coincident with the peak radio and X-ray emission. Two of these are resolved, which we use to estimate the sizes of the X-ray and radio knots. The outer portion of the radio jet and a radio component to the east show no X-ray emission to a limit of about 100 times lower flux. The X-ray emission is difficult to explain with models that successfully account for extranuclear X-ray/radio structures in other active galaxies. We think the most plausible is a synchrotron self-Compton model, but this would imply extreme departures from the conventional minimum energy and/or homogeneity assumptions. We also rule out synchrotron or thermal bremsstrahlung models for the jet X-rays, unless multicomponent or ad hoc geometries are invoked.
Highlights
PKS 0637Ϫ752 was the first celestial X-ray target of the Chandra X-ray Observatory (Weisskopf et al 2000)
The quasar PKS 0637Ϫ752, the first celestial X-ray target of the Chandra X-Ray Observatory, has revealed asymmetric X-ray structure extending from 3Љ to 12Љ west of the quasar, coincident with the inner portion of the jet previously detected in a 4.8 GHz radio image (Tingay et al 1998)
For the inner portion of the radio jet, the X-ray morphology closely matches that of new Australian Telescope Compact Array radio images at 4.8 and 8.6 GHz
Summary
PKS 0637Ϫ752 was the first celestial X-ray target of the Chandra X-ray Observatory (Weisskopf et al 2000). This Letter addresses the X-ray jet, which appears as a extension from 3Љ to 11Љ.5 west of the quasar, with brighter condensations from 7Љ.5 to 9Љ.5. Definitive X-ray identification was made in the 0.3–3.5 keV band with the Einstein Observatory (Elvis & Fabbiano 1984), and numerous X-ray observations have since been made (see Yaqoob et al 1998 and references therein); none approached the subarcsecond image quality of Chandra (Jerius et al 2000) and so could not resolve the jet. Very long baseline interferometry (VLBI) space observatory program (VSOP) observations were rescheduled to overlap the Chandra observations to investigate links between the known parsec-scale jet (Tingay et al 1998) and the X-ray emission from the quasar core.
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