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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 submillimeter wavelength continuum survey of 54z∼ 6 quasars using the Submillimeter Common-User Bolometre Array-2 on the James Clerk Maxwell Telescope to study the environments aroundz∼ 6 quasars. We identified 170 submillimeter galaxies (SMGs) with above 3.5σdetections in 450 or 850μm maps. Their far-IR luminosities are (2.2–6.4) × 10¹²L_⊙, and their star formation rates are ∼400–1200M_⊙yr⁻¹. We also calculated the SMGs’ differential and cumulative number counts in a combined area of ∼620 arcmin². To a 4σdetection (at ∼5.5 mJy), SMGs’ overdensity is${0.68}_{-0.19}^{+0.21}$(±0.19), exceeding the blank-field source counts by a factor of 1.68. We find that 13/54 quasars show overdensities (at ∼5.5 mJy) ofδ_SMG∼ 1.5–5.4. The combined area of these 13 quasars exceeds the blank-field counts with the overdensity to 5.5 mJy ofδ_SMG∼${2.46}_{-0.55}^{+0.64}$(±0.25) in the regions of ∼150 arcmin². However, the excess is insignificant on the bright end (e.g., 7.5 mJy). We also compare results with previous environmental studies of Lyαemitters and Lyman break galaxies on a similar scale. Our survey presents the first systematic study of the environment of quasars atz∼ 6. 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.

 

Abstract Recent studies have revealed a strong relation between the sample-averaged black hole (BH) accretion rate (BHAR) and star formation rate (SFR) among bulge-dominated galaxies—i.e., “lockstep” BH–bulge growth—in the distant universe. This relation might be closely connected to the BH–bulge mass correlation observed in the local universe. To further understand BH–bulge coevolution, we present Atacama Large Millimeter/submillimeter Array (ALMA) CO(2–1) or CO(3–2) observations of seven star-forming bulge-dominated galaxies at z = 0.5–2.5. Using the ALMA data, we detect significant (>3 σ ) CO emission from four objects. For our sample of seven galaxies, we measure (or constrain with upper limits) their CO line fluxes and estimate their molecular gas masses ( M gas ). We also estimate their stellar masses ( M star ) and SFRs, by modeling their spectral energy distributions. Using these physical properties, we derive the gas depletion timescales ( τ dep ≡ M gas /SFR) and compare them with the bulge/BH growth timescales ( τ grow ≡ M star /SFR ∼ M BH /BHAR). Our sample generally has τ dep shorter than τ grow by a median factor of ≳4, indicating that the cold gas will be depleted before significant bulge/BH growth takes place. This result suggests that BH–bulge lockstep growth is mainly responsible for maintaining the mass relation, not creating it. We note that our sample is small and limited to z < 2.5; JWST and ALMA will be able to probe to higher redshifts in the near future. 

Abstract The MAMMOTH-1 nebula at z = 2.317 is an enormous Ly α nebula (ELAN) extending to a ∼440 kpc scale at the center of the extreme galaxy overdensity BOSS 1441. In this paper, we present observations of the CO(3 − 2) and 250 GHz dust-continuum emission from MAMMOTH-1 using the IRAM NOrthern Extended Millimeter Array. Our observations show that CO(3 − 2) emission in this ELAN has not extended widespread emission into the circum- and inter-galactic media. We also find a remarkable concentration of six massive galaxies in CO(3 − 2) emission in the central ∼100 kpc region of the ELAN. Their velocity dispersions suggest a total halo mass of M 200 c ∼ 10 13.1 M ⊙ , marking a possible protocluster core associated with the ELAN. The peak position of the CO(3 − 2) line emission from the obscured AGN is consistent with the location of the intensity peak of MAMMOTH-1 in the rest-frame UV band. Its luminosity line ratio between the CO(3 − 2) and CO(1 − 0) r 3,1 is 0.61 ± 0.17. The other five galaxies have CO(3 − 2) luminosities in the range of (2.1–7.1) × 10 9 K km s −1 pc 2 , with the star-formation rates derived from the 250 GHz continuum of (<36)–224 M ⊙ yr −1 . Follow-up spectroscopic observations will further confirm more member galaxies and improve the accuracy of the halo mass estimation.