The RAdio Galaxy Environment Reference Survey (RAGERS)

Evidence of an anisotropic distribution of submillimeter galaxies in the 4C 23.56 protocluster at z = 2.48

¹ Cosmic Dawn Center (DAWN), Copenhagen, Denmark
² DTU Space, Technical University of Denmark, Elektrovej 327, DK-2800 Kgs. Lyngby, Denmark
³ Department of Physics and Astronomy, University of British Columbia, 6225 Agricultural Rd., Vancouver V6T 1Z1, Canada
⁴ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
⁵ Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Blvd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
⁶ Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104, USA
⁷ Center for Astrophysics | Harvard and Smithsonian, 60 Garden Street, Cambridge, MA 02143, USA
⁸ Green Bank Observatory, 155 Observatory Road, Green Bank, WV 24944, USA
⁹ National Research Council, Herzberg Astronomy and Astrophysics, 5071 West Saanich Rd., Victoria V9E 2E7, Canada
¹⁰ Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
¹¹ Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
¹² Department of Physics, Lancaster University, Lancaster, UK
¹³ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹⁴ Department of Astronomy, School of Physics, Peking University, Beijing 100871, PR China
¹⁵ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
¹⁶ Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
¹⁷ Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁸ International Centre for Radio Astronomy Research, The University of Western Australia, 35 Stirling Hwy, 6009 Crawley, WA, Australia
¹⁹ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Stromlo, Australia
²⁰ National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA
²¹ European Southern Observatory, Karl-Schwarzschild-Strasse 2, Garching D-85748, Germany
²² PIFI Visiting Scientist, Purple Mountain Observatory, Np. 8 Yuanhua Road, Qixia District, Nanjing 210034, PR China
²³ Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
²⁴ Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife, Spain
²⁵ Departamento Astrofísica, Universidad de la Laguna, E-38206 La Laguna, Tenerife, Spain
²⁶ Research Center for Astronomical Computing, Zhejiang Laboratory, Hangzhou 311100, PR China
²⁷ East Asian Observatory, 660 North A’ohoku Place, Hilo, Hawaii 96720, USA
²⁸ School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
²⁹ Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA
³⁰ Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904-4325, USA
³¹ Department of Physics, McGill University, 3600 University Street, Montreal, QC H3A 2T8, Canada
³² Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo HI 96720, USA
³³ Graduate Institute of Astrophysics, National Taiwan University, Taipei, Taiwan
³⁴ Instituto Nacional de Astrofísica Óptica y Electrónica, Luis Enrique Erro 1, Tonantzintla, CP 72840 Puebla, Mexico
³⁵ Universidad de las Américas Puebla, Ex Hacienda Sta. Catarina Mártir S/N. San Andrés Cholula, Puebla 72810, Mexico
³⁶ Department of Physics, Universiti Malaya, 50603 Kuala Lumpur, Malaysia

Received: 3 November 2023
Accepted: 19 July 2024

Abstract

Context. High-redshift radio(-loud) galaxies (HzRGs) are massive galaxies with powerful radio-loud active galactic nuclei (AGNs) and serve as beacons for protocluster identification. However, the interplay between HzRGs and the large-scale environment remains unclear.

Aims. To understand the connection between HzRGs and the surrounding obscured star formation, we investigated the overdensity and spatial distribution of submillimeter-bright galaxies (SMGs) in the field of 4C 23.56, a well-known HzRG at z = 2.48.

Methods. We used SCUBA-2 data (σ ∼ 0.6 mJy) to estimate the 850 μm source number counts and examine the radial and azimuthal overdensities of the 850 μm sources in the vicinity of the HzRG.

Results. The angular distribution of SMGs is inhomogeneous around the HzRG 4C 23.56, with fewer sources oriented along the radio jet. We also find a significant overdensity of bright SMGs (S​_850 μm ≥ 5 mJy). Faint and bright SMGs exhibit different spatial distributions. The former are concentrated in the core region, while the latter prefer the outskirts of the HzRG field. High-resolution observations show that the seven brightest SMGs in our sample are intrinsically bright, suggesting that the overdensity of bright SMGs is less likely due to the source multiplicity.