  The IRAM interferometer has been used to detect the submm source HDF 850.1
found by Hughes et al. (1998) in the Hubble Deep Field. The flux density
measured at 1.3mm is 2.2 mJy, in agreement with the flux density measured at
the JCMT. The flux densities and upper limits measured at 3.4, 2.8, 1.3, 0.85,
and 0.45 mm show that the emission is from dust. We suggest that the 1.3mm dust
source is associated with the optical arc-like feature, 3-593.0, that has a
photometric redshift of about 1.7. If HDF 850.1 is at this redshift and
unlensed, its spectral energy distribution, combined with that of 3-593.0,
matches closely that of the ultraluminous galaxy VII Zw 31. Another possibility
is that the dust source may be gravitationally lensed by the elliptical galaxy
3-586.0 at a redshift of 1.
