Schedule Aug 17, 2007
Redshift Evolution of Galaxy-Scale Star Formation: Review of Theory
Bruce Elmegreen (IBM, Watson)

The most prominent processes of star formation in galactic disks with redshifts up to z~5 can be observed directly with the HST ACS. Star formation is in the form of giant clumps, containing 10^8 to 10^9 Msun, which have an exponential distribution with galactocentric radius. Computer simulations show the evolution of these clumps. Star formation in interacting galaxies out to z~1.5 looks pretty normal, although the clumps are again unusually massive. Most galaxies are smaller beyond z~1, including antenna-shaped interactions. So far, star formation appears to involve primarily gravitational instabilities in highly turbulent, high-column-density gas disks. Monolithic collapse (i.e., star formation in spheroids) does not appear relevant; evidence for early formation of ellipticals should be interpreted instead as rapid assembly of disks and smaller ellipticals in very dense environments. There is no evidence so far for triggered star formation in shells, or for blowout or feedback associated with star formation in z~2 to 5 disks. Between z~2 and z~5, star formation also occurs in compact galaxies or submm galaxies, which are usually not resolved well, so the processes involved are not yet known.

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