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Keywords:

  • galaxies: active;
  • galaxies: individual: PKS B2152−699;
  • galaxies: jets;
  • radio continuum: galaxies;
  • X-rays: galaxies

ABSTRACT

PKS B2152−699, which has radio power characteristic of sources that dominate radio feedback, is exceptional in showing a wide range of features associated with radio-galaxy/gas interactions. We present new deep radio (Australia Telescope Compact Array), X-ray (Chandra) and ground-based optical observations, and test the energetics of the feedback model. We report the first high-resolution observations of the radio jet, finding that the inner jet extends ∼8.5 kpc (10° viewing angle) in the direction of an optical emission-line high-ionization cloud (HIC) before taking a zigzag path to a position offset from the HIC. Jet synchrotron radiation to X-ray energies is seen. The HIC is associated with cool, kT∼ 0.3 keV, X-ray gas of anomalously low metallicity. On larger scales, the radio galaxy displays all three X-ray features that together confirm supersonic expansion of the lobes into the external medium: gas cavities, inverse Compton emission showing excess internal lobe pressure, and high-contrast arms of temperature above the kT∼ 1 keV ambient medium. The well-formed southern lobe on the counterjet side is expanding with a Mach number between 2.2 and 3. The lobe energy appears to be more gently dissipated in the north. We estimate a cavity power ∼3 × 1043 erg s−1, which falls well below previously reported correlations with radio power. The total inferred time-averaged jet power, ∼4 × 1044 erg s−1, is dominated by the kinetic and thermal energy of shocked gas, and if used instead would bring the source into better agreement with the correlations. The southern hotspot is the more complex, with a spiral polarization structure. Its bright peak emits synchrotron X-rays. The fainter northern hotspot is particularly interesting, with X-rays offset in the direction of the incoming jet by ∼1 arcsec relative to the radio peak. Here modest (δ∼ 6) relativistic beaming and a steep radio spectrum cause the jet to be X-ray bright through inverse Compton scattering before it decelerates. With such beaming, a modest proton content or small departure from minimum energy in the jet will align estimates of the instantaneous and time-averaged jet power. The hotspots suggest acceleration of electrons to a maximum energy ∼1013 eV in the jet termination shocks.