Metal-Free Gas Supply at the Edge of Reionization: Late-Epoch Population III Star Formation - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




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Abstract: While the average metallicity of the intergalactic medium rises aboveZ~10^{-3} Zsun by the end of the reionization, pockets of metal-free gas canstill exist at later times. We quantify the presence of a long tail in theformation rate of metal-free halos during late stages of reionization redshiftz~6, which might offer the best window to detect Population III stars. Usingcosmological simulations for the growth of dark matter halos, coupled withanalytical recipes for the metal enrichment of their interstellar medium, weshow that pockets of metal-free gas exist at z~6 even under the assumption ofhigh efficiency in metal pollution via winds. A comoving metal-free haloformation rate d^2n-dtdV > 10^{-9} Mpc^{-3}yr^{-1} is expected at z=6 for haloswith virial temperature T {vir}~10^4 K mass ~10^8 Msun, sufficient toinitiate cooling even with strong negative radiative feedback. Under theassumption of a single Population III supernova formed per metal-free halo, weexpect an observed supernova rate of 2.6x10^{-3} deg^{-2}yr^{-1} in the sameredshift range. These metal-free stars and their supernovae will be isolatedand outside galaxies at distances >150 h^{-1} kpc and thus significantly lessbiased than the general population of ~10^8 Msun halos at z~6. Supernovasearches for metal-free explosions must thus rely on large area surveys. Ifmetal-free stars produce very luminous supernovae, like SN2006gy, then amulti-epoch survey reaching m AB =27 at 1 micron is sufficient for detectingthem at z=6. While the Large Synoptic Survey Telescope will not reach thisdepth in the z band, it will be able to detect several tens of Population IIIsupernovae in the i and r bands at z <5.5, when their observed rate is down to3-8x10^{-4} deg^{-2} yr^{-1}.



Author: Michele Trenti 1, Massimo Stiavelli 2, Michael Shull 1 1 U. Colorado, 2 STScI

Source: https://arxiv.org/







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