We report ROSAT PSPC spatial and spectral analyses of the eight B2 radio galaxies NGC 315, NGC 326, 4C 35.03, B2 0326]39, NGC 2484, B2 1040]31, B2 1855]37, and 3C 449, expected to be representative of the class of low-power radio galaxies. Multiple X-ray components are present in each, and the gas components have a wide range of linear sizes and follow an extrapolation of the cluster X-ray luminosity/temperature correlation, implying that there is no relationship between the presence of a radio galaxy and the gas fraction of the environment. No large-scale cooling Ñows are found. There is no correlation of radio-galaxy size with the scale or density of the X-ray atmosphere. This suggests that processes on scales smaller than those of the overall gaseous environments are the major inÑuence on radio-source dynamics. The intergalactic medium is usually sufficient to conÐne the outer parts of the radio structures, in some cases even to within 5 kpc of the core. In the case of NGC 315, an extrapolation suggests that the pressure of the atmosphere may match the minimum pressure in the radio source over a factor of D40 in linear size (a factor of D1600 in pressure).

The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1111/j.1745-3933.2006.00146.

We have observed the twin‐jet radio galaxy 3C 296 with Chandra. X‐ray emission is detected from the nucleus, from the inner parts of the radio jet and from a small‐scale thermal environment around the jet deceleration region. As we have found in previous observations of other twin‐jet radio galaxies, the X‐ray jet and a steep pressure gradient in the external thermal environment are associated with the region where strong bulk deceleration of the jet material is suggested by radio observations. Our observations provide additional evidence that the inner jets of twin‐jet objects are always associated with a relatively cool, dense central X‐ray emitting component with a short cooling time.

We investigate the structure of the kpc‐scale jet in the nearby (z= 0.073) radio galaxy 3C 15, using new optical Hubble Space Telescope (HST) ACS/F606W polarimetry together with archival multiband HST imaging, Chandra X‐ray data and 8.4‐GHz VLA radio polarimetry. The new data confirm that synchrotron radiation dominates in the optical. With matched beams, the jet is generally narrower in the optical than in the radio, suggesting a stratified flow. We examine a simple two‐component model comprising a highly relativistic spine and lower‐velocity sheath. This configuration is broadly consistent with polarization angle differences seen in the optical and radio data. The base of the jet is relatively brighter in the ultraviolet and X‐ray than at lower energies, and the radio and optical polarization angles vary significantly as the jet brightens downstream. Further out, the X‐ray intensity rises again and the apparent magnetic field becomes simpler, indicating a strong shock. Modelling the synchrotron spectrum of this brightest X‐ray knot provides an estimate of its minimum internal pressure, and a comparison with the thermal pressure from X‐ray emitting gas shows that the knot is overpressured and likely to be a temporary, expanding feature.