EXTREMELY METAL-POOR STARS IN THE MILKY WAY: A SECOND GENERATION FORMED AFTER REIONIZATION

Journal Article · Sat Mar 20 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/712/1/435· OSTI ID:21394267

Trenti, Michele

Cosmological simulations of Population III star formation suggest an initial mass function (IMF) biased toward very massive stars (M {approx}> 100 M{sub sun}) formed in minihalos at redshift z {approx}> 20, when the cooling is driven by molecular hydrogen. However, this result conflicts with observations of extremely metal-poor (EMP) stars in the Milky Way (MW) halo, whose r-process elemental abundances appear to be incompatible with those expected from very massive Population III progenitors. We propose a new solution to the problem in which the IMF of second-generation stars formed at z {approx}> 10, before reionization, is deficient in sub-solar mass stars, owing to the high cosmic microwave background temperature floor. The observed EMP stars are formed preferentially at z {approx}< 10 in pockets of gas enriched to metallicity Z {approx}> 10{sup -3.5} Z{sub sun} by winds from Population II stars. Our cosmological simulations of dark matter halos like the MW show that current samples of EMP stars can only constrain the IMF of late-time Population III stars, formed at z {approx}< 13 in halos with virial temperature T{sub vir} {approx} 10{sup 4} K. This suggests that pair instability supernovae were not produced primarily by this population. To begin probing the IMF of Population III stars formed at higher redshift will require a large survey, with at least 500 and probably several thousand EMP stars of metallicities Z {approx} 10{sup -3.5} Z{sub sun}.

• OSTI ID: 21394267
• Journal Information: Astrophysical Journal, Vol. 712, Issue 1; Other Information: DOI: 10.1088/0004-637X/712/1/435; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
COSMOLOGY
HYDROGEN
MASS
METALS
MILKY WAY
NONLUMINOUS MATTER
R PROCESS
RED SHIFT
RELICT RADIATION
SIMULATION
SUPERNOVAE
BINARY STARS
ELECTROMAGNETIC RADIATION
ELEMENTS
ERUPTIVE VARIABLE STARS
EVOLUTION
GALAXIES
MATTER
MICROWAVE RADIATION
NONMETALS
RADIATIONS
STAR EVOLUTION
STARS
VARIABLE STARS