Euclid Survey - Euclid

Euclid Deep Fields

The location of the three Euclid deep fields have been selected by the Euclid Sky Survey Working Group of the Euclid Consortium. These three dark patches of the sky will be the subject of the mission's deepest observations, aiming at exploring faint objects in the early Universe as well as assessing the purity of the spectroscopic observations in the Wide Survey.

The position of the Euclid Deep Fields – one in the northern sky and two in the southern sky – was announced during the 2019 annual consortium meeting in Helsinki, Finland.

See ESA web story on : Three dark fields for Euclid's deep survey

The Euclid Deep Field North – highlighted in yellow, towards the top left in this view – has an area of 20 square degrees and is located very close to the Northern Ecliptic Pole, in the constellation Draco, the dragon. The proximity to the ecliptic pole ensures maximum coverage throughout the year; the exact position was chosen to obtain maximum overlap with one of the deep fields surveyed by NASA's infrared workhorse, the Spitzer Space Telescope.

Based on the need for a larger area of calibration observations for the Euclid spectroscopic sample characterisation, the Euclid Science Team has endorsed in April 2022 the request to extend the Euclid Deep Field North from 10 deg2 to 20 deg2.

The 3 Euclid Deep Fields (EDFs) are specified as follows, in Equatorial (celestial) coordinates (RA/Dec.):

EDFN (North) - 17:58:55.9 +66:01:03.7
- 20 deg² x 40 visits
EDFS (South) - 04:04:57.84 -48:25:22.8
- 23 deg² x 45 visits
- Note that the exact centre of the EDFS has been slightly modified July 10th, 2019. The updated EDFS octagon stadium envelope is:
          63.25 -45.67
          65.35 -46.10
          66.40 -47.25
          65.99 -48.72
          59.25 -51.19
          56.95 -50.82
          55.90 -49.40
          56.80 -47.99
EDFF (Fornax) - 03:31:43.6 -28:05:18.6
- 10 deg² x 52 visits, 7 visits within a few hours-days every ~9 months

"Blue" grism data will be obtained for all observations of the 3 deep fields, as opposed to the Wide Survey where only "red" grism data will be obtained. See also NISP description at https://sci.esa.int/web/euclid/-/euclid-nisp-instrument.

The Euclid deep field spectroscopy data will be a unique dataset since there are no slitless surveys implemented with such a large number of grism orientations. The deep fields will be crucial to asess the purity and completeness of the wide field.

The Euclid deep fields will be also covered in depth by the Rubin telescope.

The Euclid wide and deep surveys. Credit: ESA/Euclid Consortium. Acknowledgment: Euclid Consortium Survey Group