Carbon-Enhanced Metal-poor Stars, the Cosmic Microwave Background, and the Stellar Initial Mass Function in the Early Universe

Published 2007 July 18 © 2007. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation Jason Tumlinson 2007 ApJ 664 L63 DOI 10.1086/520930

1538-4357/664/2/L63

Abstract

The characteristic mass of stars at early times may have been higher than today's, owing to the cosmic microwave background (CMB). This study proposes that (1) the testable predictions of this "CMB-IMF" hypothesis are an increase in the fraction of carbon-enhanced metal-poor (CEMP) stars with declining metallicity and an increase from younger to older populations at a single metallicity (e.g., disk to halo), and (2) these signatures are already seen in recent samples of CEMP stars and can be better tested with anticipated data. The expected spatial variation may explain discrepancies of CEMP frequency among published surveys. The ubiquity and time dependence of the CMB will substantially alter the reconstruction of star formation histories in the Local Group and early universe.

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10.1086/520930