Resolving the Submillimeter Background: The 850 Micron Galaxy Counts

Recent deep blank-field submillimeter surveys have revealed a population of luminous high-redshift galaxies that emit most of their energy in the submillimeter. The results suggest that much of the star formation at high redshift may be hidden to optical observations. In this Letter we present wide-area 850 μm Submillimeter Common-User Bolometer Array data on the Hawaii Survey Fields SSA13, SSA17, and SSA22. Combining these new data with our previous deep-field data, we establish the 850 μm galaxy counts from 2 to 10 mJy with a greater than 3 σ detection limit. The area coverage is 104 arcmin² to 8 mJy and 7.7 arcmin² to 2.3 mJy. The differential 850 μm counts are well described by the function n(S)=N₀/(a+S^3.2), where S is the flux in mJy, N₀ = 3.0 × 10⁴ deg^-2 mJy^-1, and a=0.4-1.0 is chosen to match the 850 μm extragalactic background light. Between 20% and 30% of the 850 μm background resides in sources brighter than 2 mJy. Using an empirical fit to our data above 2 mJy constrained by the extragalactic background light at lower fluxes, we argue that the bulk of the 850 μm extragalactic background light resides in sources with fluxes near 1 mJy. The submillimeter sources are plausible progenitors of the present-day spheroidal population.