AAS 204th Meeting, June 2004
Session 34 Detecting the First Stars and AGN
Topical Session, Tuesday, June 1, 2004, 8:30-10:00am, 10:45am-12:30pm, 2:30-4:00pm, 4:15-6:00pm, 707/709

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[34.12] The Critical Metallicity for Cosmic Star Formation

R. Schneider (Enrico Fermi Center (Rome), INAF/Osservatorio Astrofisico di Arcetri), A. Ferrara, R. Salvaterra (SISSA/International School for Advanced Studies), K. Omukai (Division for Theoretical Astrophysics, National Astronomical Observatory)

Theoretical results from cosmological simulations suggest that the first (also Pop III) stars formed in the universe were very massive (M = 100 Msun). However, stars observed today have masses roughly 100 times smaller.

We then argue, by means of detailed numerical models, that a transition from such massive to a ``normal'' cosmic star formation mode must have occurred which was governed by the metallicity of star-forming clouds; the critical metallicity value Zcr=10-5\pm 1 Zsun divides the two regimes.

Hence the relevance of Pop III stars depends on the efficiency of cosmic metal enrichment from the first supernova explosions, i.e. the chemical feedback.

We discuss in detail a number of detectable consequences of such scenario, ranging from cosmic reionization and metal footprints of Pop III stars to low-redshift/local relics of such peculiar early cosmic star formation activity.

The author(s) of this abstract have provided an email address for comments about the abstract: raffa@arcetri.astro.it

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