Kavli Affiliate: Linhua Jiang
| Summary:
The formation of the first supermassive black holes is expected to have occurred in some most pronounced matter and galaxy overdensities in the early universe. We have conducted a sub-mm wavelength continuum survey of 54 $zsim6$ quasars using the Submillimeter Common-User Bolometre Array-2 (SCUBA2) on the James Clerk Maxwell Telescope (JCMT) to study the environments around $z sim 6$ quasars. We identified 170 submillimeter galaxies (SMGs) with above 3.5$σ$ detections at 450 or 850 um, maps. Their FIR luminosities are 2.2 – 6.4 $times$ 10$^12 L_odot$, and star formation rates are $sim$ 400 – 1200 M$_odot$ yr$^-1$. We also calculated the SMGs differential and cumulative number counts in a combined area of $sim$ 620 arcmin$^2$. To a $4σ$ detection (at $sim$ 5.5 mJy), SMGs overdensity is $0.68^+0.21_-0.19$($pm0.19$), exceeding the blank field source counts by a factor of 1.68. We find that 13/54 quasars show overdensities (at $sim$ 5.5 mJy) of $δ_SMGsim$ 1.5 – 5.4. The combined area of these 13 quasars exceeds the blank field counts with the overdensity to 5.5 mJy of dsmg $sim$ $2.46^+0.64_-0.55$($pm0.25$) in the regions of $sim$ 150 arcmin$^2$. However, the excess is insignificant on the bright end (e.g., 7.5 mJy). We also compare results with previous environmental studies of Lyman alpha emitters (LAEs) and Lyman-Break Galaxies (LBGs) on a similar scale. Our survey presents the first systematic study of the environment of quasars at $zsim6$. The newly discovered SMGs provide essential candidates for follow-up spectroscopic observations to test whether they reside in the same large-scale structures as the quasars and search for protoclusters at an early epoch.
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