SIMBAD references

We have searched for ¹²CO(1->0) and ¹²CO(2->1) emission towards six globular clusters with the IRAM 30-m telescope. At a very low noise level (rms between 3 and 12mK) we found no evidence of CO signals. Our derived 3σ upper limits are below the solar mass for the molecular content of these objects, down to 0.07M_☉ for NGC 5272. Since mass loss from AGB stars and post-turnoff stars should provide up to 100M_☉ of intracluster gas between two disk crossings, we conclude that the gas must have been removed through ram-pressure stripping in a hot gaseous halo, as suggested by recent [OIII] and X-ray observations. For some clusters however, the present hot gas density in the halo is not sufficient for efficient ram-pressure stripping.