Cold gas in a complete sample of group-dominant early-type galaxies
  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.
