Michigan Technological University
Department of Physics

is pleased to announce a colloquium

with

Ken Wantanabe

Constraining the Cosmic Star Formation Rate with the MeV Background

The Cosmic Gamma-ray Background (CGB) in the MeV regime has been measured with CGRO/COMPTEL (Weidenspointner et al. 1999) and SMM (Watanabe et al. 1997). The origin of the CGB in this energy regime is believed to be dominated by gamma-rays from Type Ia supernovae. We calculate the CGB spectrum within the framework of the standard Friedmann-Robertson-Walker (FRW) cosmology as a function of the cosmic star formation rate (SFR) (Watanabe et al. 1999). Several new estimates of SFR(z) have been published since the pioneering work of Madau et al. (1996). We discuss the observational constraints on SFR(z) derived from models of the CGB. In particular, we investigate the SFR obtained from Gamma-Ray Burst observations (Schaefer et al. 2002), which increases dramatically with redshift beyond z ~ 1 in contrast to most SFR estimates which saturate with lookback time. Gamma-Ray bursts may be the most powerful tracer of star formation in the early universe and thus provide the signposts of the initial burst of element synthesis. The gamma-ray fireworks that accompanied this era is contained in the relic CGB which serves us today as a diagnostic tool of early star formation and thus chemical evolution in the early universe.

Monday, August 21, 2003

2:30 p.m., Fisher 101

Refreshments will be served

MTU | Physics | Colloquium