Galaxies 09: Assembly, Gas Content and Star Formation History of Galaxies
Kartik Sheth
Caltech / NRAO
Dependence of Galactic Structure on the Dynamical State of Galaxies
How does the formation of galactic structure depend on the dynamic state of the disk? We have addressed this question using kinematic data from the DEEP2 survey and accompanying HST imaging data from the AEGIS survey in a sample of galaxies between 0.2 $< z <$ 0.84. We find that the dispersion-dominated systems, where $\sigma~>$~v$_{rot}$, are either compact ($<$~5 kpc) systems, or are clump-cluster/chain galaxies. The latter are believed to be proto-galaxies caught in the act of building their disks via vigorous bursts of star formation. In contrast, the rotation-dominated systems (v$_{rot} >$ 30 km/s $>> \sigma$) are more ``normal'' disks with bars and spiral arms. As in the local Universe, not all rotationally dominated disks have bars suggesting that the cold dynamic state of the disk is a necessary but not a sufficient condition for the formation of bars. We also find three examples of clump-cluster/proto-bar systems which show bar-like structures in dynamically hot, i.e. dispersion dominated galaxies - the nature of these galaxies is not fully understood.
Our study is a prelude to the detailed dynamical analysis of galaxies that will be possible with gas observations using ALMA and the eVLA over the time of galaxy formation and evolution. JWST will be provide observations of the underlying stellar content in galaxies over cosmic time. Together these facilities will be cornerstones to trace the assembly and evolution of galaxies.
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