The Cosmic Near Infrared Background III: Fluctuations, Reionization and the Effects of Minimum Mass and Self-regulation

TL;DR

This paper models the fluctuations in the Near Infrared Background caused by early galaxies during reionization, using advanced simulations to infer properties of dark matter halos and the effects of star formation suppression.

Contribution

It extends previous work by employing higher-resolution simulations and improved radiative transfer to analyze NIRB fluctuations and reionization effects.

Findings

C_l shape is sensitive to halo mass and star formation suppression.

Suppression of small halos steepens the C_l spectrum.

No turnover observed in l^2 C_l at high l.

Abstract

Current observations suggest that the universe was reionized sometime before z~6. One way to observe this epoch of the universe is through the Near Infrared Background (NIRB), which contains information about galaxies which may be too faint to be observed individually. We calculate the angular power spectrum (C_l) of the NIRB fluctuations caused by the distribution of these galaxies. Assuming a complete subtraction of any post-reionization component, C_l will be dominated by galaxies responsible for completing reionization (e.g., z~6). The shape of C_l at high l is sensitive to the amount of non-linear bias of dark matter halos hosting galaxies. As the non-linear bias depends on the mass of these halos, we can use the shape of C_l to infer typical masses of dark matter halos responsible for completing reionization. We extend our previous study by using a higher-resolution N-body simulation, which can resolve halos down to 10^8 M_sun. We also include improved radiative transfer, which allows for the suppression of star formation in small-mass halos due to photo-ionization heating. As the non-linear bias enhances the dark-matter-halo power spectrum on small scales, we find that C_l is steeper for the case with a complete suppression of small sources or partial suppression of star formation in small halos (the minimum galaxy mass is M_min=10^9 M_sun in ionized regions and M_min=10^8 M_sun in neutral regions) than the case in which these small halos were unsuppressed. In all cases, we do not see a turn-over toward high l in the shape of l^2 C_l.