In this thesis I present new interferometric <sup>12</sup>CO observations of 30 early-type galaxies (ETGs). These galaxies were the brightest ~2/3 of CO detected ETGs from the complete, volume limited Atlas<sup>3D</sup> survey. By including literature data I construct the largest ever sample of mapped ETGs, containing 41 objects, and use this sample to analyse the morphology, kinematics and origin of the molecular gas. Many of the galaxies in this sample have relaxed molecular discs, but polar structures, rings, bars and disturbed gas distributions are also present. Around half of the galaxies have molecular gas that follows the stellar light profile, similar to molecular gas in spirals, while others have molecular gas excesses, truncations, rings or composite profiles. The molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but the size distributions are similar once scaled by the galaxies optical/stellar characteristic scalelengths. Cluster environments, however, lead to systems having denser, more compact molecular reservoirs. I find that molecular gas is an excellent kinematic tracer, even in high-mass ETGs, and thus molecules may be the kinematic tracer of choice for probing the M/L evolution of galaxies over cosmic-time. I use this knowledge to construct the first ever early-type CO Tully-Fisher relation, and show that it is offset from the Tully-Fisher relation of spirals by 0.98±0.22 magnitudes at Ks-band. I find that a third of my sample galaxies have their molecular and ionised gas kinematically misaligned with respect to the stars, setting a strong lower limit on the importance of externally acquired gas (e.g. from mergers and cold accretion). The origin of the molecular gas seems to depend strongly on environment, with externally acquired material being common in the field but nearly completely absent in Virgo. Furthermore, my results suggest that galaxy mass may be an important independent factor associated with the origin of the gas, with the most massive fast-rotating galaxies in our sample always having kinematically aligned gas.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:556470 |
| Date | January 2011 |
| Creators | Davis, Timothy A. |
| Contributors | Bureau, Martin |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:f84cd7df-9ad0-4bd2-8e0b-6ef36719ae1b |
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