AAS 197, January 2001
Session 73. Gamma Ray Bursts Observations and Analysis
Display, Wednesday, January 10, 2001, 9:30am-7:00pm, Exhibit Hall

## [73.06] Do the GRBs Trace the SFR? -- Testing Models of the Observed Gamma-Ray Burst Redshift Distribution

S. Seagroves, S. Thorsett (Astronomy & Astrophysics, UCSC)

It is widely believed that the gamma-ray bursts (GRBs) are linked with the deaths of massive stars, and thus should trace massive star formation. Unfortunately, directly comparing the observed redshift distribution of GRBs with the distribution expected from the star formation rate (SFR) is unwise. This is due to selection effects that bias against the redshift determination of high-z bursts. We present a form of the V/V\rm{max} test that allows us to treat the complicated selection functions for each burst in a straightforward way. This allows us to use the set of spectroscopically-determined GRB redshifts to test models of the GRB progenitor density evolution. We apply this test to determine if the observed GRB redshift distribution is consistent with a density evolution that traces the SFR. Examined are three models of the SFR that span reasonable estimates, as well as a simple null-hypothesis that the GRB redshift distribution traces a constant comoving density. The current data are enough to afford some discriminatory power among the models. Results of the tests will be discussed.