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Two sub-millimetre bright protoclusters bounding the epoch of peak star-formation activity

Lacaille, Kevin M. and Chapman, Scott C. and Smail, Ian and Steidel, C. C. and Blain, A. W. and Geach, J. and Golob, A. and Gurwell, M. and Ivison, R. J. and Reddy, N. and Sawicki, M. (2019) Two sub-millimetre bright protoclusters bounding the epoch of peak star-formation activity. Monthly Notices of the Royal Astronomical Society, 488 (2). pp. 1790-1812. ISSN 0035-8711.

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We present James Clerk Maxwell Telescope Submillimetre Common-User Bolometer Array 2 (SCUBA-2) 850 and 450 μm observations (σ_(850) ∼ 0.5 mJy, σ_(450) ∼ 5 mJy) of the HS1549+19 and HS1700+64 survey fields containing two of the largest known galaxy overdensities at z = 2.85 and 2.30, respectively. We detect 56 sub-millimetre galaxies (SMGs) with SNR > 4 over ∼50 arcmin^2 at 850 μm with flux densities of 3–17 mJy. The number counts indicate overdensities in the 3-arcmin diameter core region (∼1.5 Mpc at z = 2.5) of 6^(+4)_(−2)× (HS1549) and 4^(+6)_(−2)× (HS1700) compared to blank field surveys. Within these core regions, we spectroscopically confirm that approximately one-third of the SMGs lie at the protocluster redshifts for both HS1549 and HS1700. We use statistical identifications of other SMGs in the wider fields to constrain an additional four candidate protocluster members in each system. We combine multiwavelength estimates of the star-formation rates (SFRs) from Lyman-break dropout- and narrow-band-selected galaxies, and the SCUBA-2 SMGs, to estimate total SFRs of 12 500 ± 2800 M⊙ yr^(−1) (4900 ± 1200 M⊙ yr^(−1)) in HS1549 (HS1700), and SFR densities (SFRDs) within the central 1.5-Mpc diameter of each protocluster to be 3000 ± 900 M⊙ yr^(−1) Mpc^(−3) (1300 ± 400 M⊙ yr^(−1) Mpc^(−3)) in the HS1549 (HS1700) protocluster, ∼10^4 × larger than the global SFRDs found at their respective epochs, due to the concentration of star-forming galaxies in the small volume of the dense cluster cores. Our results suggest centrally concentrated starbursts within protoclusters may be a relatively common scenario for the build-up of mass in rich clusters assembling at z ≳ 2.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lacaille, Kevin M.0000-0001-9870-5663
Smail, Ian0000-0003-3037-257X
Steidel, C. C.0000-0002-4834-7260
Blain, A. W.0000-0001-7489-5167
Geach, J.0000-0003-4964-4635
Gurwell, M.0000-0003-0685-3621
Ivison, R. J.0000-0001-5118-1313
Reddy, N.0000-0001-9687-4973
Sawicki, M.0000-0002-7712-7857
Additional Information:© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 June 12. Received 2019 May 3; in original form 2018 September 18. Published: 26 June 2019. KL acknowledges NSGS and OGS for support. SCC acknowledges NSERC and CFI for support. IRS acknowleges support from the ERC advanced Grant DUSTYGAL (321334), STFC (ST/P000541/1), and a Royal Society/Wolfson Merit Award. This work is based on observations carried out with the the James Clerk Maxwell Telescope. The James Clerk Maxwell Telescope is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan, Academia Sinica Institute of Astronomy and Astrophysics, the Korea Astronomy and Space Science Institute, the National Astronomical Observatories of China and the Chinese Academy of Sciences (Grant No. XDB09000000), with additional funding support from the Science and Technology Facilities Council of the United Kingdom and participating universities in the United Kingdom and Canada. The James Clerk Maxwell Telescope has historically been operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the National Research Council of Canada and the Netherlands Organization for Scientific Research. Additional funds for the construction of SCUBA-2 were provided by the Canada Foundation for Innovation. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil). Facilities: James Clerk Maxwell Telescope (JCMT) (Holland et al. 2013), Submillimeter Array (SMA), and Gemini. Software: STARLINK (Currie et al. 2014), SMURF (Chapin et al. 2013; Jenness et al. 2013), PYTHON version 2.7, MATPLOTLIB (Hunter 2007), ASTROPY (Astropy Collaboration 2013), and APLPY (Robitaille & Bressert 2012).
Group:Astronomy Department
Funding AgencyGrant Number
Nova Scotia Graduate ScholarshipUNSPECIFIED
Ontario Graduate ScholarshipUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Canada Foundation for InnovationUNSPECIFIED
European Research Council (ERC)321334
Science and Technology Facilities Council (STFC)ST/P000541/1
Chinese Academy of SciencesXDB09000000
Subject Keywords:galaxies: clusters: general, galaxies: high-redshift, cosmology: observations, sub-millimetre: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20190912-081725307
Persistent URL:
Official Citation:Kevin M Lacaille, Scott C Chapman, Ian Smail, C C Steidel, A W Blain, J Geach, A Golob, M Gurwell, R J Ivison, N Reddy, M Sawicki, Two sub-millimetre bright protoclusters bounding the epoch of peak star-formation activity, Monthly Notices of the Royal Astronomical Society, Volume 488, Issue 2, September 2019, Pages 1790–1812,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98599
Deposited By: Tony Diaz
Deposited On:12 Sep 2019 17:18
Last Modified:12 Dec 2020 00:40

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