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Extended X-ray emission from the BL Lac object PKS 0521-365

M. J. Hardcastle·D. M. Worrall·M. Birkinshaw
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Abstract

Models that seek to unify BL Lacs and low-power radio galaxies predict that the two types of object should show similar isotropically emitted X-ray emission. Testing this is usually limited by difficulties in separating strong X-ray emission from a BL Lac nucleus and surrounding low-surface brightness emission. In this paper we report ROSAT HRI observations of the z=0.055 BL Lac object PKS 0521-365. We are able to separate a luminous extended X-ray component from the bright nucleus. Using a new radio map, we show that it is unlikely that the extended emission is due to inverse-Compton scattering of photons from the active nucleus, and instead interpret it as thermal emission from dense, rapidly cooling gas. This is a more extreme environment than is found in typical FRI radio galaxies, and may pose a problem for unified models.

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M. J. Hardcastle, D. M. Worrall, M. Birkinshaw. 1998-12-08. Extended X-ray emission from the BL Lac object PKS 0521-365. https://doi.org/10.1046/j.1365-8711.1999.02353.x

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