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Near-infrared background anisotropies from diffuse intrahalo light of galaxies


Unresolved anisotropies of the cosmic near-infrared background radiation are expected to have contributions from the earliest galaxies during the epoch of reionization1,2,3,4,5 and from faint, dwarf galaxies at intermediate redshifts6,7. Previous measurements8,9,10,11,12 were unable to pinpoint conclusively 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 subarcminute to one-degree angular scales, and find the clustering amplitude to be larger than predicted by the models based on 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. However, a physical mechanism that increases the clustering amplitude is needed. Motivated by recent results related to the extended stellar light profile in dark-matter haloes13,14,15, we consider the possibility that the fluctuations originate from 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 per cent relative to the total luminosity in dark-matter haloes of 109 to 1012 solar masses at redshifts of about 1 to 4.

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Figure 1: The angular power spectrum of the unresolved near-infrared background.
Figure 2: The IHL fraction from diffuse stars as a function of the halo mass.
Figure 3: The spectral energy distribution of infrared background anisotropies.

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We acknowledge support from NSF CAREER (to A.C.), NASA ADAP and an award from JPL/Caltech. We thank R. Arendt for sharing his IRAC self-calibration code. We thank J. Bock and M. Zemcov for their contributions to the SDWFS project. This work is based on observations made with the Spitzer Space Telescope. This work also made use of data products provided by the NOAO Deep Wide-Field Survey. A.C. thanks the Aspen Center for Physics for hospitality.

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Authors and Affiliations



A.C. planned the study, developed the IHL model, supervised the research work of J.S., F.D.B., C.C.F. and Y.G., and wrote the draft version of this paper. J.S. and C.C.F. performed the power spectrum measurements and F.D.B. interpreted those measurements with a halo model for the IHL. Y.G. developed a model for the high-redshift galaxies. All other co-authors contributed extensively and equally by their varied contributions to the SDWFS project (led by D.S. as the Principal Investigator), planning of SDWFS observations, analysis of SDWFS data, and by commenting on this manuscript as part of an internal review process.

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Correspondence to Asantha Cooray.

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The authors declare no competing financial interests.

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This file contains Supplementary Text and Data 1-8, Supplementary Figures 1-13, Supplementary Table 1 and additional references. (PDF 2380 kb)

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Cooray, A., Smidt, J., De Bernardis, F. et al. Near-infrared background anisotropies from diffuse intrahalo light of galaxies. Nature 490, 514–516 (2012).

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