Radio, optical and X-ray observations of PKS 2250-41: a jet/galaxy collision?
Abstract
New optical, radio and X-ray observations are used to investigate the morphology, ionization and kinematics of extended structures in the host galaxy of the radio source PKS 2250-41 (z=0.308). The data provide clear evidence for a powerful interaction between the radio jets and the ambient interstellar medium. Not only do [O III] emission-line images show spectacular extended arc structures associated with the radio lobes on both sides of the galaxy nucleus on a scale of 40-65kpc, but there is also large depolarization in the western radio lobe at the position of the western emission-line arc. Optical long-slit spectra of the extended emission-line regions provide the first convincing evidence that the radio jets can have a major ionizing effect on the warm gas in powerful radio galaxies: while the low-ionization [N II] and [S II] lines are broad (FWHM~300-500 kms^-1) across the entire emission-line nebulosity, the higher ionization [O III] lines are significantly narrower in the western emission-line arc (FWHM=240+/-10 kms^-1). This anticorrelation between linewidth and ionization is difficult to explain in terms of central source photoionization, but is entirely consistent with the compression or direct ionization effects of fast shocks driven by the radio jets. Further evidence for shocks is provided by the minimum in the ionization state at the position of the radio lobes, and by [O III](5007+4959)/4300 and He II/Hβ diagnostic ratios which are more consistent with shocks than with photoionization. The spectacular nature of the jet/cloud interaction in this object is best explained in terms of a direct collision between the radio jet and a companion galaxy in the surrounding group. This model is supported by the detection of a blue continuum source in the western arc with a colour and luminosity characteristic of late-type spiral galaxies.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 1997
- DOI:
- 10.1093/mnras/286.3.558
- Bibcode:
- 1997MNRAS.286..558C
- Keywords:
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- GALAXIES: ACTIVE;
- GALAXIES: INTERACTIONS;
- GALAXIES: JETS;
- RADIO CONTINUUM: GALAXIES;
- X-RAYS: GALAXIES