We present millimeter wavelength detections of three faint sources that are most likely high-redshift starburst galaxies .
For one of the sources , which was previously discovered with SCUBA at 850 \mu m , we present a detection with the IRAM interferometer at 240 GHz ( 1.25 mm ) that shows the object unresolved at an angular resolution of 2. ^ { \prime \prime } 5 , and coincident within 1 ^ { \prime \prime } with a radio source and a galaxy detected in the near-infrared .
The two other sources were discovered in a deep 250 GHz ( 1.2 mm ) survey with the Max-Planck Millimeter Bolometer ( MAMBO ) array at the IRAM 30 m telescope .
Both have fluxes of \approx 4 mJy and radio counterparts with a 1.4 GHz flux density of \approx 75 ~ { } \mu Jy .
Their radio–to–mm flux ratios suggest redshifts larger than 2 .
Both sources are faint in the optical and near-infrared , one showing a 20.5 mag K -band counterpart .
From our data and that available in the literature , we estimate the redshift distribution of twenty-two faint mm and sub-mm sources and conclude that the majority of them are likely to be at z > 2 .