The Hawaii SCUBA-2 Lensing Cluster Survey: Radio-detected Submillimeter Galaxies in the HST Frontier Fields

In this second paper of the Hawaii SCUBA-2 Lensing Cluster Survey series, we cross-match SCUBA-2 maps with 3 and 6 GHz images from the Janksy-VLA Frontier Fields Legacy Survey for three cluster fields, MACS J0416.1--2403, MACS J0717.5+3745, and MACS J1149.5+2223. Within the HST coverage, 14 out of 44 850 $\mu$m sources have 3 GHz counterparts, five of which are also detected at 6 GHz. The 850 $\mu$m flux densities of these detected sources span from 0.7 to 4.4 mJy after correcting for lensing amplification. The median redshift of the sample is $z = 1.28^{+0.07}_{-0.09}$, much lower than the typical redshifts ($z = 2-3$) of brighter submillimeter galaxies in the literature. In addition, we find that our sources have lower dust temperatures than those of the brighter submillimeter galaxies. This is also confirmed by an analysis of the ratio between infrared star formation rate and 850 $\mu$m flux density. However, these 14 sources may not represent the general submillimeter population at the same flux range, given that the SCUBA-2 sources without radio counterparts are likely at higher redshifts. Detection of these sources would require deeper radio images or submillimeter interferometry.