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AR 13886 (Archival Research)

Sun Jul 14 19:42:45 GMT 2024

Principal Investigator: Asantha Cooray
PI Institution: University of California - Irvine
Investigators (xml)

Title: Behind the Mask: Are First-Light Galaxies or Intrahalo-Light Stars Dominating the Unresolved IR background Fluctuations?
Cycle: 22

Abstract
Observations of the near-infrared {near-IR} background are extremely important for investigating the formation and evolution of first galaxies. The unresolved IR fluctuations in Spitzer/IRAC maps have been interpreted as due to faint galaxies present during reionization at z > 6. These galaxies have flux densities that fall below the point source detection threshold in even deeper IRAC maps. A new measurement of the fluctuation power spectrum with IRAC was shown by us to be more consistent with a model involving the intrahalo light {IHL} or the integrated emission from diffuse halo stars stripped during mergers and satellite accretion at z of 1 to 3. A multi-wavelength study can separate the two and place reliable limits on the surface density of z > 6 galaxies based on the Lyman drop-out nature of fluctuations from high redshifts at optical wavelengths relative to near-IR fluctuations. As part of CANDELS we have carried out such a study in GOODS fields using ACS/F814W and WFC3/F125W and F160W. We have obtained first limits on the UV luminosity density of the universe from faint galaxies with intensity fluctuations. The proposed archival analysis is aimed at extending the current study to wide area CANDELS fierlds {UDS, COSMOS, EGS}, to improve statistical errors and reduce cosmic variance. We will also carry out a cross-correlation of intensity fluctuations against a map of the dark matter with weak lensing in the COSMOS. Such a cross-correlation is needed to improve halo model for IHL and to better separate the high-redshift signal in the intensity fluctuations.