Abstract
We present a new infrared survey covering the threeEucliddeep fields and four otherEuclidcalibration fields usingSpitzerSpace Telescope’s Infrared Array Camera (IRAC). We combined these new observations with all relevant IRAC archival data of these fields in order to produce the deepest possible mosaics of these regions. In total, these observations represent nearly 11 % of the totalSpitzerSpace Telescope mission time. The resulting mosaics cover a total of approximately 71.5 deg2in the 3.6 and 4.5 μm bands, and approximately 21.8 deg2in the 5.8 and 8 μm bands. They reach at least 24 AB magnitude (measured to 5σ, in a 2″.5 aperture) in the 3.6 μm band and up to ∼5 mag deeper in the deepest regions. The astrometry is tied to theGaiaastrometric reference system, and the typical astrometric uncertainty for sources with 16 < [3.6]< 19 is ≲0″.15. The photometric calibration is in excellent agreement with previous WISE measurements. We extracted source number counts from the 3.6 μm band mosaics, and they are in excellent agreement with previous measurements. Given that theSpitzerSpace Telescope has now been decommissioned, these mosaics are likely to be the definitive reduction of these IRAC data. This survey therefore represents an essential first step in assembling multi-wavelength data on theEucliddeep fields, which are set to become some of the premier fields for extragalactic astronomy in the 2020s.
Highlights
The Euclid mission will survey 15 000 deg2 of the extragalactic sky to investigate the nature of dark energy and dark matter and to study the formation and evolution of galaxies (Laureijs et al 2011)
Three ‘deep’ fields were selected by the Euclid Consortium. They are described in detail in Scaramella et al, which gives references to prior studies; we give just a very brief description here. They are as follows: (1) Euclid Deep Field North (EDF-N), a roughly circular, 10 deg2 region centred on the well-studied north Ecliptic pole; (2) Euclid Deep Field Fornax (EDF-F), roughly circular and of 10 deg2, centred on the Chandra Deep Field South (CDF-S, Mauduit et al 2012; Lacy et al 2021), and including the GOODS-S (Giavalisco et al 2004) and the Hubble Ultra Deep Field (HUDF, Beckwith et al 2006); and (3) the Euclid Deep Field South (EDF-S), a pill-shaped area of 20 deg2 with no previous dedicated observations
We present the Spitzer Space Telescope (Werner et al 2004) component of the Cosmic Dawn Survey, which consists of (1) observing the full extent of the deep fields at 3.6 and 4.5 μm, and (2) processing the new observations together with all relevant archival Infrared Array Camera (IRAC) data, including data at 5.8 and 8.0 μm obtained during the cryogenic mission, and tying them to the latest Gaia astrometric reference system
Summary
The Euclid mission will survey 15 000 deg of the extragalactic sky to investigate the nature of dark energy and dark matter and to study the formation and evolution of galaxies (Laureijs et al 2011). We present the Spitzer Space Telescope (Werner et al 2004) component of the Cosmic Dawn Survey, which consists of (1) observing the full extent of the deep fields at 3.6 and 4.5 μm (only small parts of the EDF-N and EDF-F had already been observed with IRAC, see above), and (2) processing the new observations together with all relevant archival IRAC data, including data at 5.8 and 8.0 μm obtained during the cryogenic mission, and tying them to the latest Gaia astrometric reference system In this way, we strive to produce the deepest possible and most modern MIR images (mosaics) of the deep and calibration fields. These provide unique constraints on cosmic reionisation, as the brightest galaxies form in the highest density regions of the Universe, which are expected to be the sites of the first generation of stars and galaxies, and of reionisation bubbles (Trac et al 2008)
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