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Abstract 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 (±0.19), exceeding the blank-field source counts by a factor of 1.68. We find that 13/54 quasars show overdensities (at ∼5.5 mJy) ofδSMG∼ 1.5–5.4. The combined area of these 13 quasars exceeds the blank-field counts with the overdensity to 5.5 mJy ofδSMG∼ (±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.
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This content will become publicly available on June 1, 2026
Modeling submillimeter galaxies in cosmological simulations: Contribution to the cosmic star formation density and predictions for future surveys
Context.Submillimeter galaxies (SMGs) constitute a key population of bright star-forming galaxies at high-redshift. These galaxies challenge galaxy formation models, particularly regarding the reproduction of their observed number counts and redshift distributions. Furthermore, although SMGs contribute significantly to the cosmic star formation rate density (SFRD), their precise role remains uncertain. Upcoming surveys, such as the Ultra Deep Survey with the TolTEC camera, are expected to offer valuable insights into SMG properties and their broader impact in the Universe. Aims.Robust modeling of SMGs in a cosmological representative volume is necessary to investigate their nature in preparation for next-generation submillimeter surveys. Here, we test different parametric models for SMGs in large-volume hydrodynamical simulations, assess their contribution to the SFRD, and build expectations for future submillimeter surveys. Methods.We implement and test parametric relations derived from radiative transfer calculations across three cosmological simulation suites: EAGLE, IllustrisTNG, and FLAMINGO. We place particular emphasis on the FLAMINGO simulations due to their large volume and robust statistical sampling of SMGs. Based on the model that best reproduces observational number counts, we forecast submillimeter fluxes within the simulations, analyze the properties of SMGs, and evaluate their evolution over cosmic time. Results.Our results show that the FLAMINGO simulation reproduces the observed redshift distribution and source number counts of SMGs without requiring a top-heavy initial mass function. On the other hand, the EAGLE and IllustrisTNG simulations show a deficit of bright SMGs. We find that SMGs with S850 > 1 mJy contribute up to ∼27% of the cosmic SFRD atz ∼ 2.6 in the FLAMINGO simulation, which is consistent with recent observations. Flux density functions reveal a rise in SMG abundance fromz = 6 toz = 2.5 that is followed by a sharp decline in the number of brighter SMGs fromz = 2.5 toz = 0. Leveraging the SMG population in FLAMINGO, we forecast that the TolTEC UDS will detect ∼80 000 sources over 0.8 deg2at 1.1 mm (at the 4σdetection limit), capturing about 50% of the cosmic SFRD atz ∼ 2.5.
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- Award ID(s):
- 2206705
- PAR ID:
- 10636303
- Publisher / Repository:
- Astronomy & Astrophysics
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 698
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A236
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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