Carbon-Enhanced Metal-Poor Stars, the Cosmic Microwave Background, and the Stellar IMF in the Early Universe

Abstract

The characteristic mass of stars at early times may have been higher than today 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.

7 pages emulateapj format, three figures, accepted for ApJ Letters

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Cited by in corpus (10)

• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• Carbon-Enhanced Metal-Poor Stars. III. Main-Sequence Turn-Off Stars from the SDSS/SEGUE Sample
• Decoding the stellar fossils of the dusty Milky Way progenitors
• Could the Ultra Metal-poor Stars be Chemically Peculiar and Not Related to the First Stars?
• The Impact of Carbon Enhancement on Extra Mixing in Metal-Poor Stars
• Unusual neutron-capture nucleosynthesis in a carbon-rich Galactic bulge star
• Searching for Dust around Hyper Metal-Poor Stars
• Origin of metals in old Milky Way halo stars based on GALAH and Gaia
• Predicting metallicities and carbon abundances from Gaia XP spectra for (carbon-enhanced) metal-poor stars