A Search for Molecular Gas in GHz Peaked Spectrum Radio Sources
  We present searches for molecular gas (CO, OH, CS, and Ammonia) in six GHz Peaked Spectrum (GPS) radio sources. We do not detect gas in any source and place upper limits on the mass of molecular gas which are generally in the range 1E9 to a few times 1E10 solar masses. These limits are consistent with the following interpretations: (1) GPS sources do not require very dense gas in their hosts, and (2) The GPS sources are unlikely to be confined by dense gas and will evolve to become larger radio sources. 
C. P. O'Dea, J. Gallimore, C. Stanghellini, S. A. Baum, J. M. Jackson