MOLECULAR GAS IN POWERFUL RADIO GALAXIES DETECTED BY IRAS

Results are presented from the first phase of a CO(J = 1 --> 0) line s urvey of powerful radio galaxies (log P408 MHz greater than or similar to 23.5 W Hz-1). Eight radio galaxies detected by IRAS have been obse rved to a sensitivity limit of approximately 1.0 mK rms (45 km s-1 res olution) using the new 3 mm SIS receiver on the NRAO 12 m telescope; f ive sources were detected. These observations include the CO detection of the highly variable, compact flat-spectrum radio galaxy 3C 120, de tections of four galaxies from the Bologna B2 radio sample, and establ ishment of sensitive upper limits on the molecular gas content of the very powerful radio galaxies 4C 29.30, 3C 321, and Cygnus A (3C 405). These data have doubled the number of CO detections of powerful radio galaxies, allowing us to begin exploration of the full range of CO lum inosities characteristic of this class of objects. The range of comput ed molecular gas masses, log M(H-2)/M. = 9.42 - 10.34, is approximatel y 1-7 times the H-2 mass of the Milky Way and is in stark contrast to the low molecular gas masses found in radio-quiet far-infrared-selecte d elliptical galaxies, log M(H-2)/M. approximately 7-8. The relatively high CO detection rate for the current sample suggests that rich supp lies of molecular gas may be ubiquitous in powerful radio-selected gal axies detected by IRAS. The infrared luminosity to molecular gas mass ratio, L(ir)/M(H-2), in powerful radio galaxies observed in CO is in t he range approximately 15 L. M-1 to > 100 L. M-1, typical of the range of values found in infrared-luminous nuclear starbursts and AGNs. The CO(J = 1 --> 0) line widths of 3C 120, B2 0722 + 300, and B2 1318 + 3 43 are very broad (FWZI greater than or similar to 500 km s-1) compare d to normal galaxies, but consistent with previously observed interact ing/merging galaxies. The CO profile for B2 1506 + 345 is bimodal; bot h components of this galaxy pair each contain approximately 10(10) M. of molecular gas. The new CO observations support the hypothesis that powerful radio galaxies originate in colliding disk galaxies which evo lve into gas-rich, peculiar E/SO galaxies during the merger process.