A SCUBA-2 850 mu m survey of heavily reddened quasars at z similar to 2

Abstract

We present new 850 p.m SCUBA-2 observations for a sample of 19 heavily reddened Type-1 quasars at redshills z 2 with dust extinctions of Av 2-6 mag. Three of the 19 quasars arc detected at >3a significance corresponding to an 850 um flux-limit of--Z4,8 mly. Assuming the 850 ttm flux is dominated by dust heating due to star formation, very high star formation rates (SFR) of 2500-4500 Mo yr 1 in the quasar host galaxies are inferred. Even when considering a large contribution to the 850 um flux from dust heated by the quasar itself, significant SFRs of 600-1500 ME, yr 1 are nevertheless inferred for two of the three detected quasars. We stack the remaining 16 heavily reddened quasars and derive an average 3a upper limit on the SFRs in these quasar host galaxies of <880 yr-1. The number counts of sub-mm galaxies in the total survey area (134.3 arcmin2) are consistent with predictions from blankfield surveys. There are, however, individual quasars where we find evidence for an excess of associated sub-mm galaxies. For two quasars, higher spatial resolution and spectroscopic ALMA observations confirm the presence of an excess of sub-mm sources. We compare the 850 um detection rate of our quasars to both unobscured, ultraviolet luminous quasars as well as the much more obscured population of mid-infrared luminous hot Dust Obscured Galaxies (HotDOGs). When matched by luminosity and redshift, we find no significant differences in the 850 p.m flux densities of these various quasar populations given the current small sample sizes.