Extragalactic surveys are, like a wedding cake, layered in increasing
depth but decreasing area. The Chandra COSMOS Survey hits a sweet spot
among the wedding cake layers: deep enough to find obscured AGN with
optical galaxy continua and wide enough to have large samples and to
find unusual, rare objects. Yet, the Chandra COSMOS Survey sources are
bright enough that virtually all X-ray sources can be identified and
followed up across their spectral energy distributions, especially
with optical or near-IR spectroscopy, using the vast COSMOS
multiwavelength photometric and spectroscopic database.
Highlights from the Chandra COSMOS Survey include:
The best candidate recoiling supermassive black hole being ejected
out of its galaxy (CID-42 ).
The largest sample of high redshift quasars in X-rays to date.
The first large scale structures
at z>4, including one at z=5.3;
these protoclusters will become the rich clusters of galaxies we see
COSMOS is a pan-chromatic - radio to X-ray - survey of a patch of the
sky both large enough (2 sq.deg) and deep enough (AB~26 at the optical wavelength) to study
galaxy and quasar evolution up to high redshifts in typical
environments, with minimal 'cosmic bias' . Almost all major telescopes
have observed this field deeply. From space - Hubble, Spitzer,
Herschel, GALEX, XMM-Newton. Ground-based - VLA, Subaru, CTIO, KPNO,
CFHT, Magellan, VLT. The central region (~1sq.deg) has been targeted
with even deeper surveys by Chandra, VLT, HST (CANDELS), VISTA.
The location of COSMOS near the equator (10h +02deg) allows access by
all future facilities (esp. JVLA, ALMA).
Chandra is observing the entire field to a depth of ~2e-16 cgs with
ACIS in the 0.5 - 2keV band, spending nearly 2 days at each location
(~180 ksec exposure). The first phase was the Chandra COSMOS Survey
(C-COSMOS), a 1.8 Megasecond GO program (PI: Martin Elvis, Cycle 8)
covering the central 0.9 sq. deg. C-COSMOS found 1761 X-ray sources,
97% of them having optical or infrared counterparts. Only 2 sources
are truly empty fields.
The second phase was approved in Chandra Cycle 14: the 2.8 Megasecond
'COSMOS Legacy' survey (PI: Francesca Civano), the second largest
Chandra GO program awarded in 14 years. COSMOS-Legacy will complete
the Chandra coverage of the full COSMOS field to the same depth,