Spitzer Very Deep Survey of the HST/CANDELS Fields

Giovanni Fazio, Matthew Ashby, James Dunlop, Eiichi Egami, Sandra Faber, Henry Ferguson, Norman Grogin, Joseph Hora, Jiasheng Huang, Anton Koekemoer, Ivo Labbe, Zhong Wang, Steven Willner

Research output: Contribution to journalArticlepeer-review


The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is a new and powerful multicycle HST treasury imaging survey. It is the next major step forward in the study of galaxy evolution in the early universe (z = 2 to 8). Using WFC3/IR and ACS, the program incorporates a two-tiered strategy: a 'Wide' component (~0.2 sq. degrees) and a 'Deep' component (~0.04 sq. degrees). Combining these fields with the ultra-deep imaging from the HST Cycle 17 HUDF09 program (~0.004 sq degrees) yields a three-tiered strategy for efficient sampling of both rare/bright and faint/common objects. This approach mitigates cosmic variance and yields statistically robust samples of galaxies out to z = 8. These early galaxies are important because they serve as beacons of the first sites of star formation, as a constraint on galaxy formation models, and as probes of reionization. A major limitation on further progress in exploring the early universe using the new CANDELS data is the relatively modest depths of the current Spitzer/IRAC mid-infrared data in these fields. IRAC adds the unique and important capability of tracing early galaxy stellar mass growth, stellar ages, and star formation rates back to z ~ 7 to 10. This Cycle-8 Spitzer Exploration Science program proposes significantly increasing the IRAC depth in the CANDELS fields to 26.8 AB mag (5 sigma, 3.6 micron; 50 hrs/pointing), thus providing deep IRAC coverage in all the CANDELS fields. With this sensitivity Spitzer/IRAC will detect every source detected in the CANDELS Wide survey, probe galaxies to z ~ 8 at ~109 Msun, and permit measurement of their spectral energy distributions. The proposed program will increase the total area mapped jointly by WFC3/IR and IRAC to 26.8 mag AB depth by a factor of ~35. This probe of the early Universe, over a relatively large area and to such a depth by HST and Spitzer/IRAC, will have a major impact on our knowledge of the galaxy evolution and leave an important legacy for years to come.
Original languageEnglish
Pages (from-to)80057
JournalSpitzer Proposal ID #80057
Publication statusPublished - 1 May 2011


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