PdBI COLD DUST IMAGING OF TWO EXTREMELY RED H - [4.5] > 4 GALAXIES DISCOVERED WITH SEDS AND CANDELS

We report Plateau de Bure Interferometer (PdBI) 1.1mmcontinuum imaging toward two extremely redH-[ 4.5] > 4 (AB) galaxies at z > 3, which we have previously discovered making use of Spitzer SEDS and Hubble Space Telescope CANDELS ultra-deep images of the Ultra Deep Survey field. One of our objects is detected on the PdBI map with a 4.3s significance, corresponding to S. (1.1 mm) = 0.78 +/- 0.18 mJy. By combining this detection with the Spitzer 8 and 24 mu m photometry for this source, and SCUBA2 flux density upper limits, we infer that this galaxy is a composite active galactic nucleus/star-forming system. The infrared (IR)-derived star formation rate is SFR approximate to 200 +/- 100M circle dot yr(-1), which implies that this galaxy is a higher-redshift analogue of the ordinary ultra-luminous infrared galaxies more commonly found at z similar to 2-3. In the field of the other target, we find a tentative 3.1 sigma detection on the PdBI 1.1 mm map, but 3.7 arcsec away of our target position, so it likely corresponds to a different object. In spite of the lower significance, the PdBI detection is supported by a close SCUBA2 3.3 sigma detection. No counterpart is found on either the deep SEDS or CANDELS maps, so, if real, the PdBI source could be similar in nature to the submillimeter source GN10. We conclude that the analysis of ultra-deep near-and mid-IR images offers an efficient, alternative route to discover new sites of powerful star formation activity at high redshifts.