Euclid preparation: I. The Euclid Wide Survey Article Swipe
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· 2021
· Open Access
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· DOI: https://doi.org/10.1051/0004-6361/202141938
· OA: W3192250102
Euclid is an ESA mission designed to constrain the properties of dark energy\nand gravity via weak gravitational lensing and galaxy clustering. It will carry\nout a wide area imaging and spectroscopy survey (EWS) in visible and\nnear-infrared, covering roughly 15,000 square degrees of extragalactic sky on\nsix years. The wide-field telescope and instruments are optimized for pristine\nPSF and reduced straylight, producing very crisp images. This paper presents\nthe building of the Euclid reference survey: the sequence of pointings of EWS,\nDeep fields, Auxiliary fields for calibrations, and spacecraft movements\nfollowed by Euclid as it operates in a step-and-stare mode from its orbit\naround the Lagrange point L2. Each EWS pointing has four dithered frames; we\nsimulate the dither pattern at pixel level to analyse the effective coverage.\nWe use up-to-date models for the sky background to define the Euclid\nregion-of-interest (RoI). The building of the reference survey is highly\nconstrained from calibration cadences, spacecraft constraints and background\nlevels; synergies with ground-based coverage are also considered. Via\npurposely-built software optimized to prioritize best sky areas, produce a\ncompact coverage, and ensure thermal stability, we generate a schedule for the\nAuxiliary and Deep fields observations and schedule the RoI with EWS transit\nobservations. The resulting reference survey RSD_2021A fulfills all constraints\nand is a good proxy for the final solution. Its wide survey covers 14,500\nsquare degrees. The limiting AB magnitudes ($5\\sigma$ point-like source)\nachieved in its footprint are estimated to be 26.2 (visible) and 24.5\n(near-infrared); for spectroscopy, the H$_\\alpha$ line flux limit is $2\\times\n10^{-16}$ erg cm$^{-2}$ s$^{-1}$ at 1600 nm; and for diffuse emission the\nsurface brightness limits are 29.8 (visible) and 28.4 (near-infrared) mag\narcsec$^{-2}$.\n
