AN ACCURATE POSITION FOR HDF 850.1: THE BRIGHTEST SUBMILLIMETER SOURCE IN THE HUBBLE DEEP FIELD-NORTH

We report a highly significant Submillimeter Array (SMA) detection of the prototypical submillimeter source HDF 850.1, which is the brightest submillimeter source in the Hubble Deep Field-North proper. The detection yields an extremely precise position of R.A.(2000) = 12h36m51.s99 and Decl.(2000) = +62012'25.''83 with a 1σ positional uncertainty of 0.''17. The position is consistent with the location of a millimeter wavelength interferometric detection and with the locations of weak Very Large Array detections at 1.4 and 8.4 GHz, but it is not consistent with any previous optical/near-infrared identifications. The source appears point-like at the 2'' resolution of the SMA, and the detected flux of 7.8 ± 1.0 mJy is consistent with the measured Submillimeter Common-User Bolometer Array (SCUBA) fluxes. We tabulate fluxes and limits on HDF 850.1 at other wavelengths. Our redshift estimate for HDF 850.1 based on the radio through mid-infrared measurements is z = 4.1+0.5-0.6. The faintness of the source at optical/near-infrared wavelengths and the high estimated redshift suggest that HDF 850.1 may be an analog of the brighter submillimeter source GOODS 850-5, which is also thought to be at z > 4. The fact that a source like HDF 850.1 should have appeared in one of the very first blank-field SCUBA observations ever made suggests that such high-redshift sources are quite common. Thus, we are led to conclude that high-redshift star formation is dominated by giant dusty star-forming galaxies, just as it is at lower redshifts.