The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution, over the approximate redshift (z) range 8-1.5. It will image >250,000 distant galaxies using three separate cameras on the Hubble Space Telescope, from the mid-ultraviolet to the near-infrared, and will find and measure Type Ia supernovae at z > 1.5 to test their accuracy as standardizable candles for cosmology. Five premier multi-wavelength sky regions are selected, each with extensive ancillary data. The use of five widely separated fields mitigates cosmic variance and yields statistically robust and complete samples of galaxies down to a stellar mass of 10 9 M to z ≈ 2, reaching the knee of the ultraviolet luminosity function of galaxies to z ≈ 8. The survey covers approximately 800 arcmin 2 and is divided into two parts. The CANDELS/Deep survey (5σ point-source limit H = 27.7 mag) covers ∼125 arcmin 2 within Great Observatories Origins Deep Survey (GOODS)-N and GOODS-S. The CANDELS/Wide survey includes GOODS and three additional fields (Extended Groth Strip, COSMOS, and Ultra-deep Survey) and covers the full area to a 5σ pointsource limit of H 27.0 mag. Together with the Hubble Ultra Deep Fields, the strategy creates a three-tiered "wedding-cake" approach that has proven efficient for extragalactic surveys. Data from the survey are nonproprietary and are useful for a wide variety of science investigations. In this paper, we describe the basic motivations for the survey, the CANDELS team science goals and the resulting observational requirements, the field selection and geometry, and the observing design. The Hubble data processing and products are described in a companion paper.

This paper describes the Hubble Space Telescope imaging data products and data reduction procedures for the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). This survey is designed to document the evolution of galaxies and black holes at z ∼ 1.5 − 8, and to study Type Ia SNe beyond z > 1.5. Five premier multi-wavelength sky regions are selected, each with extensive multiwavelength observations. The primary CANDELS data consist of imaging obtained in the Wide Field Camera 3 / infrared channel (WFC3/IR) and UVIS channel, along with the Advanced Camera for Surveys (ACS). The CANDELS/Deep survey covers ∼ 125 square arcminutes within GOODS-N and GOODS-S, while the remainder consists of the CANDELS/Wide survey, achieving a total of ∼ 800 square arcminutes across GOODS and three additional fields (EGS, COSMOS, and UDS). We summarize the observational aspects of the survey as motivated by the scientific goals and present a detailed description of the data reduction procedures and products from the survey. Our data reduction methods utilize the most up to date calibration files and image combination procedures. We have paid special attention to correcting a range of instrumental effects, including CTE degradation for ACS, removal of electronic bias-striping present in ACS data after SM4, and persistence effects and other artifacts in WFC3/IR. For each field, we release mosaics for individual epochs and eventual mosaics containing data from all epochs combined, to facilitate photometric variability studies and the deepest possible photometry. A more detailed overview of the science goals and observational design of the survey are presented in a companion paper.

This Special Issue of the Astrophysical Journal Letters is dedicated to presenting initial results from the Great Observatories Origins Deep Survey (GOODS) that are primarily, but not exclusively, based on multi-band imaging data obtained with the Hubble Space Telescope (HST) and the Advanced Camera for Surveys (ACS). The survey covers roughly 320 square arcminutes in the ACS F435W, F606W, F814W, and F850LP bands, divided into two well-studied fields. Existing deep observations from the Chandra X-ray Observatory (CXO) and groundbased facilities are supplemented with new, deep imaging in the optical and

We have measured the rest-frame λ ∼ 1500 Å comoving specific luminosity density of star-forming galaxies at redshift 3.5 < z < 6.5 from deep images taken with the Hubble Space Telescope (HST) and the Advanced Camera for Surveys (ACS), obtained as part of the Great Observatories Origins Deep Survey (GOODS). We used color selection criteria to construct samples of star-forming galaxies at redshifts z ∼ 4, 5 and 6, identified by the signature of the 912 Å Lyman continuum discontinuity and Lyα forest blanketing in their rest-frame UV colors (Lyman-break galaxies). The ACS samples cover ∼ 0.09 square degree, and are also relatively deep, reaching between 0.2 and 0.5 L * 3 , depending on the redshift, where L * 3 is the characteristic UV luminosity of Lyman-break galaxies at z ∼ 3. The specific luminosity density of Lyman-break galaxies appears to be nearly constant with redshift from ≈ 3 to z ∼ 6, although the measure at z ∼ 6 remains relatively uncertain, because it depends on the accurate estimate of the faint counts of the z ∼ 6 sample. If Lyman-break galaxies are fair tracers of the cosmic star formation activity, our results suggest that at z ∼ 6 the 1 Based on observations obtained with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under NASA contract NAS 5-26555.-2universe was already producing stars as vigorously as it did near its maximum several Gyr later, at 1 < ∼ z < ∼ 3. Thus, the onset of large-scale star formation in the universe is to be sought at around z ∼ 6 or higher, namely at less than ∼ 7% of the current cosmic age.

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