22March 2001CfA Colloquium


Title: Where's the Kaboom? Exploring the Star-Formation Histories of Galaxies in the Hubble Deep Fields

Speaker: Henry C. Ferguson

Abstract: This talk will discuss constraints on the bursty or episodic nature of star formation derived from galaxies in the Hubble Deep Fields. Traditional "pure-luminosity" evolution models of galaxy evolution have a star-formation rate vs. time SFR(t) that is smooth and typically monotonically declining from some early time tf. In contrast, semi-analytic hierarchical models predict variations in SFR(t) due to merging. Local fossil evidence from ages and chemical abundances of stars in the Milky Way and nearby galaxies suggests that star-formation processes were rapid in some places (e.g. elliptical galaxies and spiral galaxy bulges), and that supernova-driven winds may have played a role in terminating star formation. Processes such as tidally induced star-formation, ram-pressure stripping, variations in the UV background, etc, could also modulate SFR(t). However, even if strong variations in star-formation rates are expected, theory does not predict with any degree of certainty when these should occur or how often or in what types of galaxies. Lacking a credible theory to test, we turn to Nature to tell us what actually happened; we shall examine the constraints on SFR(t) imposed by the statistical distribution of UV-IR colors for galaxies at redshifts 0.5 < z < 3 in the Hubble Deep Fields.

Reference for students:

"The Hubble Deep Fields"Ferguson, H.C., Dickinson, M. & Williams, R. 2000, ARA&A, 38, 667

Lunch with the students will be on Friday, April 13th at 12:00 in A-101.