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

Abstract

We present high-resolution interferometric Submillimeter Array (SMA) imaging at 890 microns (~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 ~11 sigma level, while the second source is tentatively detected at the ~4 sigma 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 ~0.9-2.5x10^{13} L_sun, supporting the increasing evidence for a population 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 ratio implies z>3.5.