IRAC Deep Survey of COSMOS

Over the last four years, we have developed the COSMOS survey field with complete multi-wavelength coverage from radio to X-ray, including a total of 600 hours of Spitzer Legacy time (166 hours IRAC, 460 hours MIPS). Here we propose to deepen the IRAC 3.6 µm and 4.5 µm coverage with 3000 hours over 2.3 deg^2 area included in deep Subaru imaging. This extended mission deep survey will increase the sensitivity by a factor of 3–5. The most important impact will be that the COSMOS survey will then provide extremely sensitive photometric redshifts and stellar mass estimates for approximately a million galaxies out to z~6. We expect these data to detect approximately 1000 objects at z = 6 to 10. The data will also provide excellent temporal coverage for variability studies on timescales from days to the length of the extended mission.