[Previous] | [Session 117] | [Next]
R.I. Thompson (Steward Observatory, University of Arizona)
One of the important questions in the evolution of galaxies and the history of star formation in the Universe is whether stars form predominantly in starbursts or in steady state star formation. An anlysis of the galaxies in the NICMOS deep observations of the northern Hubble Deep Field shows how such a determination might be made. The analysis determines not only photometric redshifts but also photometric extinctions. This allows us to identify the galaxies that are undergoing starburst activity versus steady state star formation. Using a definition of a starburst as star formation rates in a galaxy that exceed 50 solar masses per year, we find that roughly half of the star formation in the field is due to starburst activity. An error analysis which includes the effect of large scale structure indicates that this ratio could be altered by a factor of 2 but it does not indicate that either form of star formation is truly dominant by a large factor. It does appear, however, that the starburst activity reached a peak at about a redshift of 2.