# The Contribution of Galaxies to the $3.4\,\mathrm{\mu m}$ Cosmic Infrared Background as Measured Using WISE

## TL;DR

This paper measures the galaxy contribution to the 3.4 micron cosmic infrared background using WISE data, finding a higher value than previous galaxy-based estimates but consistent with upper limits from other methods.

## Contribution

It provides a new measurement of the galaxy contribution to the 3.4 micron EBL based on luminosity functions and galaxy spectral energy distributions, addressing previous measurement tensions.

## Key findings

- Galaxy contribution to 3.4 micron EBL is about 9.0±0.5 kJy sr^{-1}
- Result exceeds most previous galaxy-based measurements
- Consistent with upper limits from blazar observations

## Abstract

The study of the extragalactic background light (EBL) in the optical and near infrared has received a lot of attention in the last decade, especially near a wavelength of $\lambda\approx 3.4\operatorname{\mu m}$, with remaining tension among different techniques for estimating the background. In this paper we present a measurement of the contribution of galaxies to the EBL at $3.4\operatorname{\mu m}$ that is based on the measurement of the luminosity function (LF) in Lake et al. (2018) and the mean spectral energy distribution of galaxies in Lake & Wright (2016). The mean and standard deviation of our most reliable Bayesian posterior chain gives a $3.4\operatorname{\mu m}$ background of $I_\nu = 9.0\pm0.5 \operatorname{kJy} \operatorname{sr}^{-1}$ ($\nu I_\nu = 8.0\pm0.4 \operatorname{nW} \operatorname{m}^{-2} \operatorname{sr}^{-1} e\operatorname{-fold}^{-1}$), with systematic uncertainties unlikely to be greater than $2\operatorname{kJy} \operatorname{sr}^{-1}$. This result is higher than most previous efforts to measure the contribution of galaxies to the $3.4\operatorname{\mu m}$ EBL, but is consistent with the upper limits placed by blazars and the most recent direct measurements of the total $3.4\operatorname{\mu m}$ EBL.