Harry Ferguson,, and Sandy Faber,, for the CANDELS team

The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) is an observing program designed to document the first third of galactic evolution, from z = 8 to z = 1.5. It will obtain deep images of more than 250,000 galaxies with two Hubble instruments, the Advanced Camera for Surveys (ACS) and the near-infrared channel of the Wide Field Camera 3 (WFC3). It will also discover and characterize Type Ia supernovae (SNe) beyond z = 1.5 in order to establish their accuracy as standard candles for cosmology. The survey explores five premier sky regions, each well documented by existing multi-wavelength data from Spitzer and other facilities, and by extensive spectroscopy of the brighter galaxies. The use of five widely separated fields should mitigate the risk of cosmic variance, and should result in statistically robust, complete samples of galaxies down to 109 solar masses and out to redshift z ~ 8.

The CANDELS science team includes ~100 investigators, 80% from the U.S. and 20% from other countries.

CANDELS merges two originally separate Multi-Cycle Treasury (MCT) proposals. The combined program includes a “wide” imaging survey (depth ~2 orbits of exposure time) for three separate fields totaling ~720 sq. arcmin, and a “deep” imaging survey (~12-orbit depth) for the two GOODS (Great Observatories Origins Deep Survey) regions, tiling ~60 sq. arcmin in each field. The fields surveyed encompass imaging data from the Hubble Ultra Deep Field (HUDF) program (GO 11563). Thus, CANDELS offers a three-tiered strategy to efficiently sample extragalactic objects ranging from bright and rare to faint and common. It also features an extensive search for high-redshift Type Ia SNe (the first candidate is shown in Fig. 1), as well ultraviolet exposures in the GOODS northern field.