PI: Bahram Mobasher, Space Telescope Science Institute, firstname.lastname@example.org
Address: 3700 San Martin Drive, Baltimore, MD 21218, U.S.A
CoI: N. Scoville/D. Thompson, Caltech
CoI: J. Mould/ L. Macri, NOAO
CoI: D. Sanders/L. Yan, IfA, Caltech/SSC
Title: Near-IR Survey of the HST-ACS COSMOS 2-Degree Field
Abstract: Our HST treasury proposal (PI: Nick Scoville) was recently awarded 640 orbits. This is to perform a 2 square degree imaging survey in \it i (F814W) band, using the Advance Camera for Survey (ACS) instrument. Such a wide field survey (COSMOS), combined with ground-based complementary data at other wavelengths, is essential to understand the interplay between Large Scale Structure and evolution and formation of galaxies of different types and allow searches for gravitational lenses and dark matter. The COSMOS covers the one region in parameter space completely unexplored at present by the HST. The adopted field is equatorial and accessible from both hemispheres. We propose to use the wide field near-IR instruments at KPNO (FLAMINGOS) and CTIO (ISPI) 4m telescopes to survey the 2 sq. degree COSMOS field to K_s ~ 21. This complements the COSMOS photometric datasets (X-ray, UV, optical,mid/far-IR, sub-mm and radio). The near-IR data allow accurate photometric redshift measurements (rms~ 0.070) for the total of ~ 2\times 10^6 galaxies in COSMOS. This provides the necessary redshifts for study of the formation and evolution of structures ranging from galaxies to Coma size clusters out to the epoch of peak galaxy formation (z~ 2). The K-band observations are vital to select different populations of galaxies, including Extremely Red Objects (EROs) and the most massive galaxies with M_K < -26 mag. Combined with the ACS morphologies and photometric redshifts, these will be used to understand properties and evolution of these objects and to constrain galaxy formation scenarios. \it These observations provide the deepest wide-area K-band survey for a foreseeable future. The NOAO data, together with the COSMOS HST and ancillary datasets will be made public as soon as they are reduced and catalogued.
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