## Mission Overview

### The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey ("CANDELS")

Primary Investigator: Sandra Faber

Co-Primary Investigator: Harry Ferguson

HLSP Authors: Anton Koekemoer and Norman Grogin (CANDELS HST image mosaics for all fields), Audrey Galametz and Paola Santini (CANDELS-UDS catalogs), Yicheng Guo and Thomas Dahlen (CANDELS-GOODS-S catalogs). Hooshang Nayyeri (CANDELS-COSMOS catalogs), Mauro Stefanon (CANDELS-EGS catalogs), Guillermo Barro (CANDELS multi-band catalogs for all fields), Dritan Kodra and Brett Andrews (CANDELS v2 photo-z catalogs for all fields)

Released: 2011-01-12

Updated: 2022-10-05

Primary Reference(s): Grogin et al. 2011Koekemoer et al. 2011

DOI: 10.17909/T94S3X

## Overview

The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution from z = 8 to 1.5 via deep imaging of more than 250,000 galaxies with WFC3/IR and ACS. It will also discover and characterize Type Ia SNe beyond z > 1.5 and establish their accuracy as standard candles for cosmology. The program incorporates a "Wide" imaging survey to two-orbit J+H depth over 720 sq. arcmin in the COSMOS, EGS, and UDS fields. It also includes a "Deep" imaging survey to ~12-orbit Y+J+H depth in the two GOODS fields, tiling ~60 sq. arcmin in each field. In combination with ultra-deep imaging from the Hubble Ultradeep Field program (GO 11563), the result is a three-tiered strategy that effciently samples both bright/rare and faint/common extragalactic objects. Additional information about the survey design is available on the CANDELS public web site.

###### Note:

All the mosaics provided here have already had all distortion removed by drizzling, and correct astrometry is provided in their header WCS (represented by CRVAL1, CRVAL2, CRPIX1, CRPIX2, CD1_1, CD1_2, CD2_1, CD2_2). Their CTYPE keywords also correctly reflect this (being set to "RA---TAN" and "DEC--TAN'). However, the Astropy tools "all_pix2world" or "all_world2pix" (contained in "wcs") currently attempt to apply SIP coefficients that are found in the headers, and therefore may not give correct astrometry. A solution is instead to use the Astropy tools "wcs_pix2world" or "wcs_world2pix" (also contained in "wcs"), which do not make this error and which give correct astrometry for these mosaics. Another alternative is to not use Astropy but instead use WCSTools, available from CfA, which also correctly calculates astrometry for these mosaics.

#### Acknowledgements

When using data from the CANDELS survey, please include the following acknowledgement:

"This work is based on observations taken by the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555."

Please also cite both of the following papers when discussing the CANDELS survey:

Grogin et al. 2011, ApJS, 197, 35G

Koekemoer et al. 2011, ApJS, 197, 36K

Oct. 5 2022: CANDELS Team Releases Photo-z Catalog For All Fields

The CANDELS team released the full v2 photo-z catalog for all five fields (Kodra et al. 2023). This catalog includes photo-z PDFs produced by six groups within the collaboration, recalibrated versions of those PDFs, and combinations of the recalibrated PDFs that further improve the photo-z PDF quality.  It also includes photo-z point estimates and uncertainty intervals.

Use the 'Expand All' link to see a history of previous updates for CANDELS at MAST.

## Data Products

#### Directory Structure

All CANDELS data products are organized into a subdirectory structure that follows this format:

<field>/<prod>/<ver>/

where:

• <field> = the name of the survey field, one of "cosmos", "egs", "goods-n", "goods-s", or "uds"
• <prod> = the type of product, one of "catalogs", "<epoch_name>", or "<combined_name>"
• <epoch_name> = the name of the epoch, which has the format of "cos<nn>", "egs[ab]<nn>", "gn<nn>", "gs[dw]<nn>", or "uds<nn>", depending on the survey field.  <nn> is always a zero-padded, two-digit number.
• <combined_name> = the name used for the total combined mosaics, one of "cos-tot", "egs-tot", "gn-tot", "gs-tot", or "uds-tot"
• <ver> = "v0.5" for the <epoch_name> subdirectories, "v1.0" for the <combined_name> subdirectories, or "v1" for the "catalogs/" subdirectories
• NOTE: For GOODS-N, the images are further divided into subdirectories based on the spatial resolution, one of "30mas-acs" or "60mas-all"

An example subdirectory path for one of the GOODS-S epochs is:

goods-s/gsd04/v0.5/

#### Catalog Files

For detailed information on the catalog file naming conventions, click the Expand All link.

For detailed information on the image file naming conventions, click the Expand All link.

## Citations

Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work.

Note: These HLSP data products are licensed for use under CC BY 4.0.

## References

Reminder: please always cite both Grogin et al. 2011 and Koekemoer et al. 2011 when referencing CANDELS.  The other papers are for the catalogs and should be cited, in addition, when appropriate.