The Discovery of Extended Thermal X‐Ray Emission from PKS 2152−699: Evidence for a “Jet‐Cloud” Interaction

A Chandra ACIS-S observation of PKS 2152-699 reveals thermal emission from adiffuse region around the core and a hotspot located 10" northeast from thecore. This is the first detection of thermal X-ray radiation on kiloparsecscales from an extragalactic radio source. Two other hotspots located 47"north-northeast and 26" southwest from the core were also detected. Using aRaymond-Smith model, the first hotspot can be characterized with a thermalplasma temperature of 2.6$\times10^6$ K and an electron number density of 0.17cm$^{-3}$. These values correspond to a cooling time of about 1.6$\times10^7$yr. In addition, an emission line from the hotspot, possibly Fe xxv, wasdetected at rest wavelength 10.04\AA. The thermal X-ray emission from the first hotspot is offset from the radioemission but is coincident with optical filaments detected with broadbandfilters of HST/WFPC2. The best explanation for the X-ray, radio, and opticalemission is that of a `jet-cloud' interaction. The diffuse emission around the nucleus of PKS 2152-699 can be modeled as athermal plasma with a temperature of 1.2$\times10^7$ K and a luminosity of1.8$\times10^{41}$ erg s$^{-1}$. This emission appears to be asymmetric with asmall extension toward Hotspot A, similar to a jet. An optical hotspot (EELR)is seen less than an arcsecond away from this extension in the direction of thecore. This indicates that the extension may be caused by the jet interactingwith an inner ISM cloud, but entrainment of hot gas is unavoidable. Futureobservations are discussed.Comment: To appear in the Astrophysical Journal 21 pages, 5 Postscript figures, 1 table, AASTeX v. 5.