We present the results of HST/WFPC2 medium and narrow band imaging and VLA and MERLIN2 radio imaging of three powerful radio galaxies: 3C 171, 3C 277.3, and PKS 2250-41. We obtained images of the rest frame [OIII] 5007 and [OII] 3727 line emission using the Linear Ramp Filters on WFPC2. The correlations between the emission line morphology and the [OIII]/[OII] line ratios with the radio emission seen in ground based observations are clarified by the HST imaging. We confirm that the radio lobes and hot-spots are preferentially associated with lower ionization gas. 3C 171 exhibits high surface brightness emission line gas mainly along the radio source axis. The lowest ionization gas is seen at the Eastern hot spot. In 3C 277.3 there is bright high ionization gas (and continuum) offset just to the east of the radio knot K1. Our observations are consistent with previous work suggesting that this emission is produced by precursor gas ionized by the shock being driven into the cloud by the deflected radio jet. In PKS 2250-41 we resolve the emission line arc which wraps around the outer rim of the western lobe. The lower ionization [OII] emission is nested just interior to the higher ionization [OIII] emission suggesting that we have resolved the cooling region behind the bow shock. We also detect possible continuum emission from the secondary hot-spot. Thus, our observations support the hypothesis that in these sources, the interaction between the expanding radio source and the ambient gas strongly influences the morphology, kinematics, and ionization of the gas (Refer to PDF file for exact formulas).

Publication Date



This is the pre-print of an article published by the American Astronomical Society. © 2005 The American Astronomical Society. The final, published version is located here: https://doi.org/10.1086/497265

Also archived in: arXiv: astro-ph/0507652 v1 27 Jul 2005

Support for program 6657 (PI C. Tadhunter) was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. MERLIN is operated as a National Facility by the University of Manchester on behalf of the UK Particle Physics and Astronomy Research Council.

This research made use of (1) the NASA/IPAC Extragalactic Database(NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration; and (2) NASA’s Astrophysics Data System Abstract Service. We thank Shireen Gonzaga for help with the WFPC2 observations and Peter Thomasson and Tom Muxlow for assistance with the MERLIN2 observations for 3C277.3. Karen Wills acknowledges financial support from PPARC and the Royal Society. We thank the anonymous referee for very detailed and helpful comments.

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type


Department, Program, or Center

School of Physics and Astronomy (COS)


RIT – Main Campus