Characterizing Faint Submillimeter Galaxies with Cluster Lensing

Abstract

Based on the measurements of the integrated background light from extragalactic sources, it is known that about half of the starlight is absorbed by dust and re-radiated into the far-infrared (FIR). It is therefore important to study both the unobscured and dustobscured populations of galaxies across cosmic time for a full picture of the star formation in our universe. At z > 1, the FIR emission from galaxies is redshifted to the submillimeter. However, surveys made with single-dish submillimeter telescopes are confusion limited at low uxes (< 2 mJy at 850 m) and can only detect ultra-luminous galaxies. Consequently, we have little information about fainter submillimeter galaxies (SMGs), which are actually the major contributors to the submillimeter background light and therefore the dominant star-formers in the dusty universe. Determining how much these faint SMGs overlap the optically selected samples is critical to fully account for the cosmic star formation history. Observations of massive cluster elds are the best way to study faint galaxies, thanks to gravitational lensing. To explore the faint submillimeter population, we have been observing nine galaxy clusters with the SCUBA-2 camera on the James Clerk Maxwell Telescope. We also used interferometric observations with the Karl G. Jansky Very Large Array and the Submillimeter Array to determine the accurate positions of our detected sources. Our observations have discovered a population of faint SMGs that are undetected in deep radio, optical, and near-infrared images. This suggests that a signi cant fraction of the galaxies with infrared luminosities < 1012L may be hidden from optical surveys and would not be included in the UV star formation history.