A Novel Approach to Constrain the Escape Fraction and Dust Content at High Redshift Using the Cosmic Infrared Background Fractional Anisotropy

TL;DR

This paper proposes using the fractional anisotropy of the Cosmic Infrared Background to constrain the escape fraction of ionizing photons and distinguish between dusty and dust-free high-redshift stellar populations, offering a new observational approach.

Contribution

It introduces a novel method to constrain high-redshift galaxy properties by analyzing the fractional anisotropy of the CIB, linking fluctuations to escape fraction and dust content.

Findings

Lower escape fractions lead to higher fractional anisotropy values.

Longer wavelength bands (>10 microns) show larger differences in anisotropy based on escape fraction.

Current observations can already place some constraints on the fractional anisotropy.

Abstract

The Cosmic Infrared Background (CIB) provides an opportunity to constrain many properties of the high redshift (z>6) stellar population as a whole. This background, specifically, from 1 to 200 microns, will contain any information about the era of reionization and the stars responsible for producing these ionizing photons. In this paper, we look at the fractional anisotropy delta I/I of this high redshift population, which is the ratio of the magnitude of the fluctuations (delta I) and the mean intensity (I). We show that this can be used to constrain the escape fraction of the population as a whole. The magnitude of the fluctuations of the CIB depend on the escape fraction, while the mean intensity does not. This results in lower values of the escape fraction producing higher values of the fractional anisotropy. This difference is predicted to be larger at the longer wavelengths bands (above 10 microns), albeit it is also much harder to observe in that range. We show that the fractional anisotropy can also be used to separate a dusty from a dust-free population. Finally, we discuss the constraints provided by current observations on the CIB fractional anisotropy.