UV-luminous, star-forming hosts of z similar to 2 reddened quasars in the Dark Energy Survey

We present the first rest-frame UV population study of 17 heavily reddened, high-luminosity [E(B − V)QSO ≳ 0.5; Lbol > 1046 erg s−1] broad-line quasars at 1.5 < z < 2.7. We combine the first year of deep, optical, ground-based observations from the Dark Energy Survey (DES) with the near-infrared VISTA Hemisphere Survey and UKIDSS Large Area Survey data, from which the reddened quasars were initially identified. We demonstrate that the significant dust reddening towards the quasar in our sample allows host galaxy emission to be detected at the rest-frame UV wavelengths probed by the DES photometry. By exploiting this reddening effect, we disentangle the quasar emission from that of the host galaxy via spectral energy distribution fitting. We find evidence for a relatively unobscured, star-forming host galaxy in at least 10 quasars, with a further three quasars exhibiting emission consistent with either star formation or scattered light. From the rest-frame UV emission, we derive instantaneous, dust-corrected star formation rates (SFRs) in the range 25 < SFRUV < 365 M⊙ yr−1, with an average SFRUV = 130 ± 95 M⊙ yr−1. We find a broad correlation between SFRUV and the bolometric quasar luminosity. Overall, our results show evidence for coeval star formation and black hole accretion occurring in luminous, reddened quasars at the peak epoch of galaxy formation

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

We present new 850$\mu$m SCUBA-2 observations for a sample of 19 heavily reddened Type-I quasars at redshifts $z\sim$2 with dust extinctions of A$_{\rm{V}} \simeq 2-6$ mag. Three of the 19 quasars are detected at $>$3$\sigma$ significance corresponding to an 850$\mu$m flux-limit of $\gtrsim$4.8 mJy. Assuming the 850$\mu$m flux is dominated by dust heating due to star formation, very high star formation rates (SFR) of $\sim$2500-4500 M$_\odot$ yr$^{-1}$ in the quasar host galaxies are inferred. Even when considering a large contribution to the 850$\mu$m flux from dust heated by the quasar itself, significant SFRs of $\sim$600-1500 M$_\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 3$\sigma$ upper limit on the SFRs in these quasar host galaxies of $<$880 M$_\odot$ yr$^{-1}$. The number counts of sub-mm galaxies in the total survey area (134.3arcmin$^2$) 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 850$\mu$m 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$\mu$m flux densities of these various quasar populations given the current small sample sizes

Galaxy and Mass Assembly (GAMA): The Weak Environmental Dependence of Quasar Activity at 0.1<z<0.35

Understanding the connection between nuclear activity and galaxy environment remains critical in constraining models of galaxy evolution. By exploiting extensive catalogued data from the Galaxy and Mass Assembly (GAMA) survey, we identify a representative sample of 205 quasars at 0.1 < z < 0.35 and establish a comparison sample of galaxies, closely matched to the quasar sample in terms of both stellar mass and redshift. On scales <1 Mpc, the galaxy number counts and group membership of quasars appear entirely consistent with those of the matched galaxy sample. Despite this, we find that quasars are ~1.5 times more likely to be classified as the group center, indicating a potential link between quasar activity and cold gas flows or galaxy interactions associated with rich group environments. On scales of ~a few Mpc, the clustering strength of both samples are statistically consistent and beyond 10 Mpc we find no evidence that quasars trace large scale structures any more than the galaxy control sample. Both populations are found to prefer intermediate-density sheets and filaments to either very high- or very low- density environments. This weak dependence of quasar activity on galaxy environment supports a paradigm in which quasars represent a phase in the lifetime of all massive galaxies and in which secular processes and a group-centric location are the dominant trigger of quasars at low redshift