Cosmic Infrared Background Fluctuations in Deep Spitzer IRAC Images: Data Processing and Analysis

TL;DR

This study analyzes deep Spitzer IRAC images to characterize cosmic infrared background fluctuations, employing advanced data processing to distinguish between instrumental effects and genuine cosmic signals, suggesting high-redshift or low-luminosity sources as origins.

Contribution

It introduces a detailed data reduction and analysis methodology for CIB fluctuation studies, including self-calibration, source masking, and modeling, with robust tests confirming the cosmic origin of large-scale fluctuations.

Findings

Large-scale fluctuations are not caused by bright galaxies.

Measured CIB intensity fluctuations are consistent with high-z or low-luminosity sources.

Instrumental and procedural effects are effectively mitigated.

Abstract

This paper provides a detailed description of the data reduction and analysis procedures that have been employed in our previous studies of spatial fluctuation of the cosmic infrared background (CIB) using deep Spitzer IRAC observations. The self-calibration we apply removes a strong instrumental signal from the fluctuations which would otherwise corrupt our results. The procedures and results for masking bright sources, and modeling faint sources down to levels set by the instrumental noise are presented. Various tests are performed to demonstrate that the resulting power spectra of these fields are not dominated by instrumental or procedural effects. These tests indicate that the large scale (>~30') fluctuations that remain in the deepest fields are not directly related to the galaxies that are bright enough to be individually detected. We provide the parameterization of these power spectra in terms of separate instrument noise, shot noise, and power law components. Our measurements of spatial fluctuations of the CIB intensity indicate the mean emission from the objects producing the fluctuations is quite low (>~1 nW m-2 sr-1 at 3-5 micron), and thus consistent with current gamma-ray absorption constraints. The source of the fluctuations may be high-z Population III objects, or a more local component of very low luminosity objects with clustering properties that differ from the resolved galaxies. Finally, we discuss the prospects of the upcoming space-based surveys to directly measure the epochs inhabited by the populations producing these source-subtracted CIB fluctuations, and to isolate the individual fluxes of these populations.