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A SCUBA-2 850μm survey of heavily reddened quasars at z ~ 2

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Wethers, CF 
Hewett, PC 
Jones, GC 

Abstract

We present new 850μm SCUBA-2 observations for a sample of 19 heavily reddened Type-I quasars at redshifts $z\sim2withdustextinctionsofA{\rm{V}} \simeq 2-6$ mag. Three of the 19 quasars are detected at $>3\sigma$ significance corresponding to an 850μm flux-limit of $\gtrsim4.8mJy.Assumingthe850\mu$m flux is dominated by dust heating due to star formation, very high star formation rates (SFR) of $\sim2500−4500M\odot$ yr−1 in the quasar host galaxies are inferred. Even when considering a large contribution to the 850μm flux from dust heated by the quasar itself, significant SFRs of $\sim600−1500M\odot$ yr−1 are nevertheless inferred for two of the three detected quasars. We stack the remaining 16 heavily reddened quasars and derive an average 3σ upper limit on the SFRs in these quasar host galaxies of $<880M\odot$ yr−1. The number counts of sub-mm galaxies in the total survey area (134.3arcmin2) are consistent with predictions from blank-field 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 850μm 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 850μm flux densities of these various quasar populations given the current small sample sizes.

Description

Keywords

galaxies: active, galaxies: evolution, galaxies:high redshift, quasars: general, galaxies: star formation, submillimetre: galaxies

Journal Title

Monthly Notices of the Royal Astronomical Society

Conference Name

Journal ISSN

0035-8711
1365-2966

Volume Title

492

Publisher

Oxford University Press (OUP)
Sponsorship
Science and Technology Facilities Council (ST/N000927/1)