Ultra-faint high-redshift galaxies in the Frontier Fields

TL;DR

This paper combines simulations and lens models to predict the detectability of ultra-faint, high-redshift galaxies in the Frontier Fields, revealing their potential role in cosmic reionization and constraining feedback effects on small halos.

Contribution

It introduces a method to identify extremely faint galaxies in the Frontier Fields and assesses their significance in reionization and feedback processes.

Findings

Galaxies as faint as magnitude 33-34 can be detected in Frontier Fields.

Faint galaxies in small halos dominate the ionizing photon budget.

Detection of faint galaxies constrains feedback effects on star formation.

Abstract

By combining cosmological simulations with Frontier Fields project lens models we find that, in the most optimistic case, galaxies as faint as $m \approx 33 - 34$ (AB magnitude at $1.6 \rm \mu m$) can be detected in the Frontier Fields. Such faint galaxies are hosted by dark matter halos of mass $\sim10^9 M_\odot$ and dominate the ionizing photon budget over currently observed bright galaxies, thus allowing for the first time the investigation of the dominant reionization sources. In addition, the observed number of these galaxies can be used to constrain the role of feedback in suppressing star formation in small halos: for example, if galaxy formation is suppressed in halos with circular velocity $v_c < 50$ km s$^{-1}$, galaxies fainter than $m=31$ should not be detected in the FFs.