S-CANDELS: The Spitzer-Cosmic Assembly Near-Infrared Deep Extragalactic Survey. Survey Design, Photometry, and Deep IRAC Source Counts

TL;DR

S-CANDELS is a deep infrared survey using Spitzer to detect high-redshift galaxies, providing detailed catalogs and counts that improve understanding of galaxy populations and the cosmic infrared background.

Contribution

This paper presents the survey design, data processing, and deep IRAC source catalogs from S-CANDELS, enhancing previous infrared surveys with increased depth and coverage in key extragalactic fields.

Findings

Deep IRAC counts are consistent with existing galaxy models.

No significant additional contribution to the diffuse CIB from discrete sources.

Approximately half of the CIB flux remains unresolved.

Abstract

The Spitzer-Cosmic Assembly Deep Near-Infrared Extragalactic Legacy Survey (S-CANDELS; PI G. Fazio) is a Cycle 8 Exploration Program designed to detect galaxies at very high redshifts (z > 5). To mitigate the effects of cosmic variance and also to take advantage of deep coextensive coverage in multiple bands by the Hubble Space Telescope Multi-Cycle Treasury Program CANDELS, S-CANDELS was carried out within five widely separated extragalactic fields: the UKIDSS Ultra-Deep Survey, the Extended Chandra Deep Field South, COSMOS, the HST Deep Field North, and the Extended Groth Strip. S-CANDELS builds upon the existing coverage of these fields from the Spitzer Extended Deep Survey (SEDS) by increasing the integration time from 12 hours to a total of 50 hours but within a smaller area, 0.16 square degrees. The additional depth significantly increases the survey completeness at faint magnitudes. This paper describes the S-CANDELS survey design, processing, and publicly-available data products. We present IRAC dual-band 3.6+4.5 micron catalogs reaching to a depth of 26.5 AB mag. Deep IRAC counts for the roughly 135,000 galaxies detected by S-CANDELS are consistent with models based on known galaxy populations. The increase in depth beyond earlier Spitzer/IRAC surveys does not reveal a significant additional contribution from discrete sources to the diffuse Cosmic Infrared Background (CIB). Thus it remains true that only roughly half of the estimated CIB flux from COBE/DIRBE is resolved.