An Accurate Position for HDF 850.1: The Brightest Submillimeter Source in the Hubble Deep Field-North

TL;DR

This paper precisely locates the brightest submillimeter source HDF 850.1 in the Hubble Deep Field-North, estimates its redshift at 4.1, and discusses its implications for high-redshift star formation.

Contribution

We provide the most accurate position for HDF 850.1 and estimate its redshift, confirming its high-redshift nature and its significance in understanding early universe star formation.

Findings

HDF 850.1 is at RA 12:36:51.99, Dec +62:12:25.83 with 0.17 arcsec uncertainty.

The source's flux is 7.8+/-1.0 mJy, consistent with previous measurements.

Estimated redshift of HDF 850.1 is z=4.1.

Abstract

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 RA(2000)=12:36:51.99 and Dec(2000)=+62:12:25.83 with a 1-sigma positional uncertainty of 0.17 arcsec. The position is consistent with the location of a millimeter wavelength interferometric detection and with the locations of weak VLA detections at 1.4 and 8.4 GHz, but it is not consistent with any previous optical/near-infrared identifications. The source appears pointlike at the 2 arcsec resolution of the SMA, and the detected flux of 7.8+/-1.0 mJy is consistent with the measured 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. 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.