Extremely-Metal Poor Stars in the Milky Way: A Second Generation Formed after Reionization - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado




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Abstract: Cosmological simulations of Population III star formation suggest an initialmass function IMF biased toward very massive stars M>100Msun formed inminihalos at redshift z>20, when the cooling is driven by molecular hydrogen.However, this result conflicts with observations of extremely-metal poor EMPstars in the Milky Way halo, whose r-process elemental abundances appear to beincompatible with those expected from very massive Population III progenitors.We propose a new solution to the problem in which the IMF of second-generationstars formed at z>10, before reionization, is deficient in sub-solar massstars, owing to the high cosmic microwave background temperature floor. Theobserved EMP stars are formed preferentially at z<10 in pockets of gas enrichedto metallicity Z>10^{-3.5} Zsun by winds from Population II stars. Ourcosmological simulations of dark matter halos like the Milky Way show thatcurrent samples of EMP stars can only constrain the IMF of late-time PopulationIII stars, formed at z<13 in halos with virial temperature Tvir~10^4 K. Thissuggests that pair instability supernovae were not produced primarily by thispopulation. To begin probing the IMF of Population III stars formed at higherredshift will require a large survey, with at least 500 and probably severalthousand EMP stars of metallicities Z~10^{-3.5} Zsun.



Autor: Michele Trenti 1, Michael Shull 1, 1 U Colorado

Fuente: https://arxiv.org/







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