- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Department of Physics and Astronomy University of British Columbia Canada
- Harvard-Smithsonian Center for Astrophysics United States
- University of Hong Kong China (People's Republic of)
- Harvard-Smithsonian Center for Astrophysics, Smithsonian Astrophysical Observatory United States
- Department of Physics and Astronomy University of Western Ontario Canada
- CY Cergy Paris University France
- Inter-University Centre for Astronomy and Astrophysics India
- Harvard University United States
- Inter-University Centre for Astronomy and Astrophysics India
- Paris Observatory France
- Harvard-Smithsonian Center for Astrophysics Harvard University United States
- EDP Sciences France
- University of Victoria Canada
- Université Paris Diderot France
- Presidency University India
- Collège de France France
We present IRAM 30m and APEX telescope observations of CO(1-0) and CO(2-1) lines in 36 group-dominant early-type galaxies, completing our molecular gas survey of dominant galaxies in the Complete Local-volume Groups Sample. We detect CO emission in 12 of the galaxies at >4sigma significance, with molecular gas masses in the range 0.01-6x10^8 Msol, as well as CO in absorption in the non-dominant group member galaxy NGC 5354. In total 21 of the 53 CLoGS dominant galaxies are detected in CO and we confirm our previous findings that they have low star formation rates (0.01-1 Msol/yr) but short depletion times (<1Gyr) implying rapid replenishment of their gas reservoirs. Comparing molecular gas mass with radio luminosity, we find that a much higher fraction of our group-dominant galaxies (60+-16%) are AGN-dominated than is the case for the general population of ellipticals, but that there is no clear connection between radio luminosity and the molecular gas mass. Using data from the literature, we find that at least 27 of the 53 CLoGS dominant galaxies contain HI, comparable to the fraction of nearby non-cluster early type galaxies detected in HI and significantly higher that the fraction in the Virgo cluster. We see no correlation between the presence of an X-ray detected intra-group medium and molecular gas in the dominant galaxy, but find that the HI-richest galaxies are located in X-ray faint groups. Morphological data from the literature suggests the cold gas component most commonly takes the form of a disk, but many systems show evidence of galaxy-galaxy interactions, indicating that they may have acquired their gas through stripping or mergers. We provide improved molecular gas mass estimates for two galaxies previously identified as being in the centres of cooling flows, NGC 4636 and NGC 5846, and find that they are relatively molecular gas poor compared to our other detected systems.
20 pages, 12 PDF figures, accepted by A&A. v2 adds references and acknowledgements, and corrects minor typographical errors identified at the proof stage