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abstract
We are engaged in an X-ray study of radio galaxies in order to test models which unify them with BL~Lac objects into a single class. Our sample of 14 galaxies is selected from the B2 radio catalog through identification with an elliptical galaxy brighter than $m_{\rm ph} = 15.7$ mag, redshift $< 0.06$, and extended radio power $24.0 \leq \log P_{\rm ext} \leq 25.2$ (W Hz$^{-1}$ at 1.4 GHz, $H_o = 50$ km s$^{-1}$ Mpc$^{-1}$). ROSAT measurements of the first 8 sources studied find a component which is unresolved to the PSPC (i.e., angular size $< 15''$) in addition to extended emission consistent with hot gas. The fraction of counts in the unresolved component spans a wide range, from $\sim 7\%$ to $\sim 70\%$, necessitating improvements to earlier work which compared radio galaxies and BL~Lacs under the assumption that all the X-ray emission of radio galaxies has a single origin. We use the thermal emission to study the ambient medium affecting the structure of the radio sources. The unresolved emission may be either thermal or non-thermal in origin; the support for these suggestions and the role of higher spatial resolution data from the ROSAT HRI, improved spectral data from ASCA, and careful comparison with the core radio emission, are addressed.
Support from NASA grant NAG5-1882 and NASA contract NAS8-39073 is gratefully acknowledged.
