ODIN: Confirmation and 3D Reconstruction of Six Massive Protoclusters at Cosmic Noon

Abstract Protoclusters represent sites of accelerated galaxy formation and extreme astrophysical activity characteristic of dense environments. Identifying massive protoclusters and mapping their spatial structures are therefore crucial for understanding how large-scale environment influences galaxy evolution. We combine wide-field Ly α imaging from the One-hundred-deg 2 DECam Imaging in Narrowbands survey with extensive Dark Energy Spectroscopic Instrument and ancillary spectroscopy across the extended COSMOS and XMM Large Scale Structure (LSS) fields (≈14 deg 2 ) to search for massive protoclusters. We confirm six systems at z ≈ 2.4 and ≈ 3.1, including three newly identified structures and three which overlap with previously known structures and/or systems detected using other tracers. We reconstruct their three-dimensional structures, estimate descendant halo masses, and for one structure at z ≈ 3.12, demonstrate that overlapping narrowband filters (NB497 and N501) provide accurate redshift tomography for emission-line galaxies. One protocluster at z ≈ 2.45 overlaps with one of the LATIS tomographic fields, enabling direct comparison between galaxy and H i overdensities traced by Ly α forest absorption. Another at z ≈ 3.12 hosts a massive quiescent galaxy ( M * ≈ 1.2 × 10 11 M ⊙ ), suggesting that overdense environments may play a role in accelerating galaxy assembly and quenching. Comparing Ly α emission properties across environments, we find that protocluster galaxies exhibit higher median line fluxes and a deficit of faint emitters relative to the field. The effect is strongest when combining 2D and 3D density information, indicating that galaxies in the densest protocluster cores are most affected by environmental processes. This effect is stronger at z ≈ 3.1 than at z ≈ 2.4, suggesting possible redshift evolution.

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Journal
The Astrophysical Journal
Published
2026-08-26
DOI
https://doi.org/10.3847/1538-4357/ae899d
Primary Topic
Galaxies: Formation, Evolution, Phenomena
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article
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0.00

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article

ODIN: Confirmation and 3D Reconstruction of Six Massive Protoclusters at Cosmic Noon

Byeongha Moon, Vandana Ramakrishnan, Hu Zou Hu Zou, M. Celeste Artale et al.
The Astrophysical Journal
Galaxies: Formation, Evolution, Phenomena
article

ODIN: Confirmation and 3D Reconstruction of Six Massive Protoclusters at Cosmic Noon

Byeongha Moon, Vandana Ramakrishnan, Hu Zou Hu Zou, M. Celeste Artale, Andrei Cuceu, C. Gronwall, Ethan Pinarski, Eshwar Puvvada, Dick Joyce, Paulina Troncoso, Rongpu Zhou, Yucheng Guo, Ho Seong Hwang, Peter Doel, Robert Kehoe, Davide Bianchi, Graziano Rossi, Jaime Forero, Joseph Harry Silber, Hiram K. Herrera-Alcantar, Ashley Ortiz, Rebecca Canning, Benjamin Weaver, Changbom Park, Woong-Seob Jeong, Michael Schubnell, Gregory Tarle, David Schlegel, Ana Sofia Uzsoy, Nathalie Palanque-Delabrouille, Ankit Kumar, Jaehyun Lee, Gaston Gutierrez, Seshadri Nadathur, John Moustakas, David Sprayberry, Enrique Gaztanaga, Ramon Miquel, Eric Gawiser, Axel de la Macorra, Steven Ahlen, Eusebio Sanchez, Kyoung-Soo Lee, Arjun Dey, Will Percival, Martin Landriau, Marc Manera, Satya Gontcho, J. Aguilar, August Bliese, Anand Raichoor, Francisco Prada, Anthony Kremin, Adam Myers, Todd Claybaugh, David Brooks, Yujin Yang, Hyunmi Song, Ignasi Perez-Rafols, Aaron M. Meisner, Laurent Le Guillou, Theodore Kisner, Ofer Lahav, Francisco Valdes, Lucia Guaita, Maria Cerdosino, Seong-Kook Lee
article en

Abstract

Abstract Protoclusters represent sites of accelerated galaxy formation and extreme astrophysical activity characteristic of dense environments. Identifying massive protoclusters and mapping their spatial structures are therefore crucial for understanding how large-scale environment influences galaxy evolution. We combine wide-field Ly α imaging from the One-hundred-deg 2 DECam Imaging in Narrowbands survey with extensive Dark Energy Spectroscopic Instrument and ancillary spectroscopy across the extended COSMOS and XMM Large Scale Structure (LSS) fields (≈14 deg 2 ) to search for massive protoclusters. We confirm six systems at z ≈ 2.4 and ≈ 3.1, including three newly identified structures and three which overlap with previously known structures and/or systems detected using other tracers. We reconstruct their three-dimensional structures, estimate descendant halo masses, and for one structure at z ≈ 3.12, demonstrate that overlapping narrowband filters (NB497 and N501) provide accurate redshift tomography for emission-line galaxies. One protocluster at z ≈ 2.45 overlaps with one of the LATIS tomographic fields, enabling direct comparison between galaxy and H i overdensities traced by Ly α forest absorption. Another at z ≈ 3.12 hosts a massive quiescent galaxy ( M * ≈ 1.2 × 10 11 M ⊙ ), suggesting that overdense environments may play a role in accelerating galaxy assembly and quenching. Comparing Ly α emission properties across environments, we find that protocluster galaxies exhibit higher median line fluxes and a deficit of faint emitters relative to the field. The effect is strongest when combining 2D and 3D density information, indicating that galaxies in the densest protocluster cores are most affected by environmental processes. This effect is stronger at z ≈ 3.1 than at z ≈ 2.4, suggesting possible redshift evolution.

The Astrophysical JournalVol. 1008(1)
University of Siena (IT), Rutgers, The State University of New Jersey (US), Institució Catalana de Recerca i Estudis Avançats (ES), Universitat Autònoma de Barcelona (ES), Korea Institute for Advanced Study (KR), University of Wyoming (US), Pennsylvania State University (US), Fermi National Accelerator Laboratory (US), Institute of Space Sciences (ES), Universidad Andrés Bello (CL), Seoul National University (KR), Lawrence Berkeley National Laboratory (US), University of Waterloo (CA), Universidad Nacional de Córdoba (AR), Southern Methodist University (US), Perimeter Institute (CA), Institute for High Energy Physics (ES), University of Milan (IT), Chungnam National University (KR), Chinese Academy of Sciences (CN), Purdue University West Lafayette (US), Université Paris-Saclay (FR), University of Michigan (US), Korea Astronomy and Space Science Institute (KR), Institut d'Astrophysique de Paris (FR), Brera Astronomical Observatory (IT), Sejong University (KR), Sorbonne Université (FR), Instituto de Astronomía Teórica y Experimental (AR), Institut d'Estudis Espacials de Catalunya (ES), Galaxies, Etoiles, Physique et Instrumentation (FR), Wyoming Department of Education (US), Center for Astrophysics Harvard & Smithsonian (US), Institute of Space Science - INFLPR Subsidiary (RO), Universidad de Los Andes (BO), Millennium Engineering and Integration (United States) (US), Universidad Central de Chile (CL), Instituto de Astrofísica de Andalucía (ES), Laboratoire Médiations (FR), University College London (GB), University of Virginia (US), Arizona State University (US), University of Portsmouth (GB), Universidad Nacional Autónoma de México (MX), Universitat Politècnica de Catalunya (ES)
National Science Foundation, U.S. Department of Energy, Gordon and Betty Moore Foundation, Purdue University, Ministerio de Ciencia, Innovación y Universidades, National Research Foundation, National Research Foundation of Korea, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Ministry of Science and ICT, South Korea, Agencia Nacional de Investigación y Desarrollo, Office of Science, Science and Technology Facilities Council, Agencia Estatal de Investigación, Division of Astronomical Sciences
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Galaxies: Formation, Evolution, Phenomena
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