Constraints on the star formation efficiency of galaxies during the epoch of reionization

Abstract

Reionization is thought to have occurred in the redshift range of 6 < z < 9, which is now being probed by both deep galaxy surveys and CMB observations. Using halo abundance matching over the redshift range 5 < z < 8 and assuming smooth, continuous gas accretion, we develop a model for the star formation efficiency f of dark matter halos at z > 6 that matches the measured galaxy luminosity functions at these redshifts. We find that f peaks at ∼ 30% at halo masses M ∼ 10 11 -10 12 M , in qualitative agreement with its behavior at lower redshifts. We then investigate the cosmic star formation histories and the corresponding models of reionization for a range of extrapolations to small halo masses. We use a variety of observations to further constrain the characteristics of the galaxy populations, including the escape fraction of UV photons. Our approach provides an empirically-calibrated, physically-motivated model for the properties of star-forming galaxies sourcing the epoch of reionization. In the case where star formation in low-mass halos is maximally efficient, an average escape fraction ∼ 0.1 can reproduce the optical depth reported by Planck, whereas inefficient star formation in these halos requires either about twice as many UV photons to escape, or an escape fraction that increases towards higher redshifts. Our models also predict how future observations with JWST can improve our understanding of these galaxy populations.

GOLDRUSH. II. Clustering of galaxies at z ∼ 4–6 revealed with the half-million dropouts over the 100 deg2 area corresponding to 1 Gpc3

“…SHMRs of Behroozi et al (2013b) are comparable with ours at z ∼ 4 and 5 in the massive halo of M h > 2 × 10 12 M⊙. Their estimates are higher than ours in the mass range of M h < 2 × 10 12 M ⊙ by a factor of ∼ 2, but still within their 2σ errors (see also; Sun & Furlanetto 2016;Rodríguez-Puebla et al 2017). …”

Emulating Simulations of Cosmic Dawn for 21 cm Power Spectrum Constraints on Cosmology, Reionization, and X-Ray Heating

“…These sub-parameters are therefore completely degenerate with each other in the way they affect reionization in 21cmFAST. Previous works have explored how to parameterize the mass and redshift evolution of ζ Sun & Furlanetto 2016), and this will certainly be a feature to incorporate into this framework for future studies. For the time being, we assume ζ to be a constant for intuitive purposes, similar to previous work.…”

“…For the time being, we assume ζ to be a constant for intuitive purposes, similar to previous work. Some of the fiducial values for the terms in Equation 16 are physically motivated-N γ ∼ 4000 is the expectation from spectral models of Population II stars (Barkana & Loeb 2005), and both f and f esc are thought to lie within a few factors of 0.1 (Kuhlen & Faucher-Giguère 2012;Robertson et al 2015;Paardekooper et al 2015;Xu et al 2016;Sun & Furlanetto 2016)-however, these are not strongly constrained at high redshifts and are particularly unconstrained for low-mass halos. Baryonic matter must cool in order for it to condense and allow for star formation.…”

Maximum Redshift of Gravitational Wave Merger Events

“…Thin lines correspond to the analytic prediction of [43] while thick lines are the numerical results of [40]. The contours show that at redshifts z ≤ 30 the gas infall rate increases with mass, and that for a fixed mass it decreases with increasing redshift at z ≈ 30.…”