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 submillimeter-to-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) × 10^(13) 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.