A near/mid infrared search for ultra-bright submillimetre galaxies: searching for sosmic eyelash analogues

Abstract

We present results from a near/mid IR search for submillimetre galaxies over a region of 6230 sq deg. of the southern sky. We used a cross-correlation of the VISTA Hemispheric Survey (VHS) and the WISE database to identify bright galaxies (Ks � 18.2) with near/mid IR colours similar to those of the high redshift lensed sub-mm galaxy SMM J2135-0102. We find 7 galaxies which fulfill all five adopted near/mid IR colour (NMIRQC) criteria and resemble the SED of the reference galaxy at these wavelengths. For these galaxies, which are broadly distributed in the sky, we deter- mined photometric redshifts in the range z=1.6-3.2. We searched the VHS for clusters of galaxies, which may be acting as gravitational lenses, and found that 6 out of the 7 galaxies are located within 3.5 arcmin of a cluster/group of galaxies. Using the J-Ks vs J sequences we determine photometric redshifts for these clusters/groups in the range z=0.2-0.9. We propose the newly identified sources are ultra-bright high red- shift lensed SMG candidates. Follow-up observations in the sub-mm and mm are key to determine the ultimate nature of these objects.