Chandra X-Ray Observatory Study of the X-Ray Emission of PKS 0023−26 and Comparison with Recent ALMA Results

Abstract We present a deep high-resolution Chandra X-ray Observatory study of the powerful compact radio source PKS 0023−26 associated with a quasar at redshift 0.322. Earlier studies of the optical environment suggested that the source could be located in a galaxy cluster or a group. However, we report a nondetection of hot gas on large scales (out to ∼60 kpc radius) and place an upper limit on the X-ray luminosity of &lt;3 × 10 42 erg s −1 , consistent only with the presence of a poor, low-temperature ( kT &lt; 0.5 keV) galaxy group. X-ray spectral analysis of the central circular region, r &lt; 7 kpc, shows, in addition to the mildly absorbed active galactic nucleus, a thermal emission component with a temperature of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>k</mml:mi> <mml:mi>T</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mn>9</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.37</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.19</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> keV. We discuss the origin of this hot component as a result of interaction between the evolving radio source and the interstellar medium (ISM). Our high-angular-resolution X-ray image traces the distribution of hot gas, which is closely aligned with and extends beyond the radio source, and also in the direction perpendicular to the axis of the radio source. The X-rays are enhanced in the northern radio lobe and at the location of the peak of the CO(3–2)/CO(2–1) line emission, suggesting that the interactions between the jet and cold medium result in the X-ray radiation that excites CO. The shock driven by the jet into the ISM is supersonic with a Mach number of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">M</mml:mi> </mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>1.75</mml:mn> </mml:math> –2, creating the cocoon of hot X-rays that surrounds the radio source. This result agrees with observations of shocks in other radio galaxies and points to the prevalent impact of jets on the ISM.