MEDIUM-FAR INFRARED OBSERVATIONS OF COMPACT STEEP-SPECTRUM AND GHZ PEAKED SPECTRUM RADIO GALAXIES

compact steep spectrum (css) and ghz peaked spectrum (gps) radio sources are powerful extragalactic radio sources with radio emission which is confined well within the host galaxies. they are thought to be either young objects, which have yet to develop extended radio lobes (like cygnus a), or sources where the radio emitting plasma is trapped by an unusually dense interstellar medium. by searching for emission from cold dust, we will determine which of the two scenarios is correct. in the former case, css/gps will have as much cold gas and dust as comparable power large size frii sources. in the latter case, they should be the most logical group of high redshift object in which to search for gas and dust, allowing us to extend the work on gas rich galaxies to much higher redshifts than iras was generally able to reach. as iso is not carrying out an allsky survey and the probability of finding serendipitously a sample of distant gas rich galaxies with iso is low, this sample represents an excellent chance of finding distant analogues to the ultraluminous iras galaxies. iras observations of css/gps were inconclusive, due to the limited sensitivity and the comparatively short observing wavelengths of that mission coupled with the spread of redshifts in these sources (generally considerably more distant than iras detected galaxies). iso instead has both the sensitivity and the wavelength coverage to be able to tackle this problem. we wish to observe with isophot a sample of css/gps radio galaxies, together with a comparison sample of extended objects, matched in radio luminosity and redshift, in order to determine whether there is indeed an unusually dense and cold ism in the host galaxies of css/gps radio galaxies as compared with extended radio galaxies. in either case the results are vital for a better understanding of radio source formation and developement, and of the nature of t tr [truncated!, Please see actual data for full text]