Detecting high-$z$ galaxies in the Near Infrared Background

TL;DR

This paper demonstrates that fluctuations from high-redshift ($5<z<10$) galaxies contribute a measurable fraction to the unresolved near-infrared background and can be isolated through cross-correlation with Lyman Break Galaxies.

Contribution

It introduces a method to isolate high-$z$ galaxy fluctuations in the NIRB using cross-correlation with LBGs, providing new insights into reionization sources.

Findings

High-$z$ galaxy fluctuations are several percent of NIRB fluctuations.

Cross-correlation effectively isolates high-$z$ signals at small angular scales.

Method works across different survey areas and magnitude limits.

Abstract

Emission from high-$z$ galaxies must unquestionably contribute to the near-infrared background (NIRB). However, this contribution has so far proven difficult to isolate even after subtracting the resolved galaxies to deep levels. Remaining NIRB fluctuations are dominated by unresolved low-$z$ galaxies on small angular scales, and by an unidentified component with unclear origin on large scales ($\approx 1000''$). In this paper, by analyzing mock maps generated from semi-numerical simulations and empirically determined $L_{\rm UV} - M_{\rm h}$ relations, we find that fluctuations associated with galaxies at $5 < z < 10$ amount to several percent of the unresolved NIRB flux fluctuations. We investigate the properties of this component for different survey areas and limiting magnitudes. In all cases, we show that this signal can be efficiently, and most easily at small angular scales, isolated by cross-correlating the source-subtracted NIRB with Lyman Break Galaxies (LBGs) detected in the same field by {\tt HST} surveys. This result provides a fresh insight into the properties of reionization sources.