A measurement of the intrahalo light fraction with near-infrared background anisotropies

Abstract

Unresolved near-infrared background anisotropies are expected to have contributions from the earliest galaxies during reionization 1-5 and faint, dwarf galaxies at intermediate redshifts 6, 7 . Previous measurements 8-12 were unable to conclusively pinpoint the dominant origin because they did not sample spatial scales that were sufficiently large to distinguish between these two possibilities. Here we report a measurement of the anisotropy power spectrum from sub-arcminute to one degree angular scales and find the clustering amplitude to be larger than the model predictions involving the two existing explanations. As the shot-noise level of the power spectrum is consistent with that expected from faint galaxies, a new source population on the sky is not necessary to explain the observations. A physical mechanism that increases the clustering amplitude, however, is needed. Motivated by recent results related to the extended stellar light profile in dark matter halos [13][14][15] , we consider the possibility that the fluctuations originate from diffuse intrahalo stars of all galaxies. We find that the measured power spectrum can be explained by an intrahalo light fraction of 0.07 to 0.2% relative to the total luminosity in dark matter halos of 10 9 to 10 12 solar masses at redshifts of ∼ 1 to 4.Author Contributions A.C. planned the study, developed the intrahalo light model, supervised the research work of J.S., F.D. C.F. and Y.G., and wrote the draft version of this paper. J.S. and C.F. performed the power spectrum measurements and F.D. interpreted those measurements with a halo model for the intrahalo light. Y.G. developed a model for the high-redshift galaxies. All other coauthors of this paper contributed extensively and equally by their varied contributions to the SDWFS project (led by D.S. as the PI), planning of SDWFS observations, analysis of SDWFS data, and by commenting on this manuscript as part of an internal review process.

Multi-component Decomposition of Cosmic Infrared Background Fluctuations

“…The infrared emission from these stars is called intrahalo light. To model the intrahalo light, we use an empirical luminosity function (Cooray et al 2012a):…”

“…Here c refers to IHL, EoR or low-z galaxies. We use the standard physical models in the literature to calculate the power spectra of IHL (Cooray et al 2012a), EoR (Cooray et al 2012b) andlow-z (Helgason et al 2012). The DGL and shot noise are considered known as they can be precisely fitted to the data at large and small angular scales respectively.…”

“…INTRODUCTION The optical and infrared background traces nucleosynthesis in stars and radiation from black holes throughout cosmic history. In addition to sources in our Galaxy, the absolute infrared background intensity is composed of diffuse sources of emission (Santos et al 2002), such as intra-halo light (IHL) (Cooray et al 2012a;) and faint galaxies present during the epoch of reionization (EoR). Instead of absolute intensity, which can be easily contaminated by Galactic emission, the near-infrared background may be studied using spatial fluctuations or anisotropies (Cooray 2016).…”

“…Instead of absolute intensity, which can be easily contaminated by Galactic emission, the near-infrared background may be studied using spatial fluctuations or anisotropies (Cooray 2016). These have been measured in broad continuum bands by a number of groups (Matsumoto et al 2011;Kashlinsky et al 2005;Cooray et al 2012a;Mitchell-Wynne et al 2015;). The fluctuation amplitude, which is robustly consistent across these measurements, exceeds that expected from the largescale clustering of known galaxy populations (Helgason et al 2012).…”

Searching for axion-like particle decay in the near-infrared background: an updated analysis

“…For the modeling of IHL we closely follow refs. [44] and [33], which add a diffuse extended component in addition to the standard galaxy clustering models. The IHL luminosity-mass relation is…”