For Reviewers

Modern astrophysics depends on multi-wavelength data to get a comprehensive picture of galaxy formation and evolution.  For this reason extragalactic astronomy has focused on a small number of well-studied fields that are optimized across the electromagnetic spectrum. The COSMOS field is the premier degree scale fields on the sky with some of the deepest possible data on >1 degree scales.


The field was chosen to have low backgrounds at all wavelengths, to be free of bright sources at all wavelengths, and to be visible in both hemispheres from the ground; ensuring ultra-deep imaging, large numbers of spectra, and easy follow-up observations.

Here we summarize the data that exists:


COSMOS has been covered to 75 ksec depth with XMM (6x10-15 erg cm-2 s-1 soft band), and the entire COSMOS field has been covered by Chandra to 160 ksec depth (2.2x10-16 erg cm-2 s-1 soft band).


COSMOS is in the GALEX-DIS, reaching FUV=25.5, NUV=26 magAB.

Spectroscopy and Spectroscopic follow-up

COSMOS has extensive spectroscopic data with over 97,000 spectra targeting over 68,000 unique objects.  Major surveys include zCOSMOS (~20K galaxies at z <1.2 and ~3000 at 2<z<3.5), VUDS (4000 at 2.5<z<6.5), Keck (~500 at z >4), and FMOS (>1500 at z <2) efforts.  Along with numerous smaller programs.

In ~2018, the Subaru Prime Focus Spectrograph (PFS, Ellis et al. 2012) will begin conducting a deep spectroscopic survey reaching z′~24 magAB for ~250k galaxies, and going ~1 mag deeper covering ~20k z>4 systems.


The entire COSMOS field is covered by HST with ACS-F814W band and the central 0.05O region is covered by the CANDELS survey in F606W, F125W, and F160W

Optical/NIR Imaging

COSMOS is the target of ultra-deep HSC imaging in the g,r,i,z, and y bands and deep u band imaging with both CFHT and DECcam. Subaru-Suprime-Cam has imaged the field in the 0.4-1 μm range with a combination of broad, intermediate, and narrow band filters reaches 25.5-27 magAB.  The deepest NIR imaging possible from the ground reaching ~24.5−26.5 magAB using 1200h of VISTA on the central 1.5 sq deg, and ~24AB over the full field using UKIRT and CFHT.

Mid-IR and Sub-mm

COSMOS has deep Spitzer MIPS 24 μm coverage reaching ~20 μJy rms, and are covered by Herschel-PACS to 6-12 mJy 5σ at 100 and 160 μm and Herschel-SPIRE to 8-13 mJy 5σ at 250,350, and 500 μm.  AzTEC, MAMBO, GISMO, LaBOCA, and SCUBA2 have also observed both fields at 0.4-2 mm reaching an rms of 2-9 mJy.  Furthermore over 500 ALMA pointings are available in COSMOS.


COSMOS has 10 μJy rms at 20 cm from the VLA and 2 μJy rms at 10 cm from the JVLA.  The COSMOS field has also been covered by GMRT at 60 cm and the VLA at 90 cm to 60μJy and 0.5 mJy rms respectively.


COSMOS has been announced as an LSST deep drilling field (R~28.5 ABmag), so the optical data on these fields will only deepen and temporal monitoring will continue in the next decade.


COSMOS is a calibration field for Euclid and will be observed with high-priority. It will be covered to 26–26.5 magAB in the Y, J, and H bands and receive high-resolution, deep optical imaging in the optical similar to what is currently available in COSMOS.  


SPLASH is visible to all the 20−39 m telescopes that will be operating in Hawaii and Chile by the end of the decade, enabling spectroscopy to the 27-28 magAB depth of the HSC data.


Although the SPLASH fields are at rather low ecliptic latitudes and therefore the zodiacal background is higher, the scientific payoff for JWST will be excellent because our limiting magnitude is similar to that for which JWST can obtain R~5000 spectroscopy. So SPLASH will be one of the primary sources of interesting objects for NIRSpec to observe, enabling a quick start on NIRSpec science – critical in view of the limited lifetime of JWST.