HST/STIS low dispersion spectroscopy of three Compact Steep Spectrum sources

Evidence for jet-cloud interaction

¹ Kapteyn Astronomical Institute, Groningen, 9700 AV, The Netherlands e-mail: [labiano;pdb]@astro.rug.nl
² Space Telescope Science Institute, Baltimore, MD 21218, USA e-mail: koekemoe@stsci.edu
³ Department of Physics, Rochester Institute of Technology, Rochester, NY 14623, USA e-mail: odea@cis.rit.edu
⁴ Western Kentucky University, Bowling Green, KY 42101, USA e-mail: geldermn@grendel.tccw.wku.edu
⁵ Lawrence Livermore National Lab., Livermore, CA 94550, USA e-mail: wdevries@beowulf.ucllnl.org
⁶ Department of Physics, Rochester Institute of Technology, Rochester, NY 14623, USA e-mail: djasps@rit.edu
⁷ Center for Imaging Science, Rochester Institute of Technology, Rochester, NY 14623, USA e-mail: baum@cis.rit.edu
⁸ Osservatorio Astronomico di Torino, Pino Torinesse (TO) 10025, Italy e-mail: capetti@to.astro.it
⁹ Istituto di Radioastronomia del CNR, Bologna 40129, Italy e-mail: rfanti@ira.cnr.it
¹⁰ Netherlands Foundation for Astronomy, Dwingeloo 7990 AA, The Netherlands e-mail: morganti@astron.nl
¹¹ University of Sheffield, Western Bank, Sheffield S10 2TN, UK e-mail: C.Tadhunter@sheffield.ac.uk

Received: 23 November 2004
Accepted: 4 March 2005

Abstract

We present Hubble Space Telescope Imaging Spectrograph long-slit spectroscopy of the emission line nebulae in the compact steep spectrum radio sources 3C 67, 3C 277.1, and 3C 303.1. We derive BPT (Baldwin- Philips-Terlevich; Baldwin et al. 1981) diagnostic emission line ratios for the nebulae which are consistent with a mix of shock excitation and photo-ionization in the extended gas. In addition, line ratios indicative of lower ionization gas are found to be associated with higher gas velocities. The results are consistent with a picture in which these galaxy scale radio sources interact with dense clouds in the interstellar medium of the host galaxies, shocking the clouds thereby ionizing and accelerating them.