Identification of two bright z > 3 submillimeter galaxy candidates in the COSMOS field

Abstract

We present high-resolution interferometric Submillimeter Array imaging at 890 μm (∼2″ resolution) of two millimeter selected galaxies - MMJ100015+021549 and MMJ100047+021021 - discovered with the Max-Planck Millimeter Bolometer (MAMBO) on the IRAM 30 m telescope and also detected with Bolocam on the CSO, in the COSMOS field. The first source is significantly detected at the ∼11σ level, while the second source is tentatively detected at the ∼4σ level, leading to a positional accuracy of ∼0″.2-0″.3. MM100015+021549 is identified with a faint radio and K-band source. MMJ100047+021021 shows no radio emission and is tentatively identified with a very faint K-band peak which lies at ∼1″.2 from a clumpy optical source. The submillimeterto-radio flux ratio for MM100015+021549 yields a redshift of ∼4.8, consistent with the redshift implied by the UV-to-submillimeter photometry, z ∼ 3.0-5.0. We find evidence for warm dust in this source with an infrared luminosity in the range ∼(0.9-2.5) × 1013 L⊙, supporting the increasing evidence for a population of luminous submillimeter galaxies at z > 3. Finally, the lack of photometric data for MMJ100047+021021 does not allow us to investigate its properties in detail; however, its submillimeter-to-radio flux ratio implies z > 3.5. © 2010. The American Astronomical Society. All rights reserved.