Probing the fluctuating Ultra-violet background using the Hubble Frontier Fields

TL;DR

This paper proposes a method to probe the fluctuating ultraviolet background during reionization by analyzing the faint-end slope of the UV luminosity function in different cosmic volumes, using a simple model and future JWST data.

Contribution

It introduces a proof-of-concept approach to constrain UV background fluctuations by measuring the faint-end slope of the UV luminosity function across different regions.

Findings

Current data insufficient to constrain alpha in different fields.

Future JWST observations of Hubble Frontier Fields will enable testing of the method.

Model links UV feedback to the faint-end slope of the luminosity function.

Abstract

In recent years, the rise in the number of Lyman Break Galaxies detected at high redshifts z >= 6 has opened up the possibility of understanding early galaxy formation physics in great detail. In particular, the faint-end slope (alpha) of the Ultra-violet luminosity function (UV LF) of these galaxies is a potential probe of feedback effects that suppress star formation in low mass haloes. In this work, we propose a proof-of-concept calculation for constraining the fluctuating UV background during reionization by constraining alpha in different volumes of the Universe. Because of patchy reionization, different volumes will experience different amount of photo-heating which should lead to a scatter in the measured alpha. Our approach is based on a simple model of the UV LF that is a scaled version of the halo mass function combined with an exponential suppression in the galaxy luminosity at the faint-end because of UV feedback. Although current data is not sufficient to constrain alpha in different fields, we expect that, in the near future, observations of the six lensed Hubble Frontier Fields with the James Webb Space Telescope (JWST) will offer an ideal test of our concept.