Diverse Protoclusters at z∼3 Disclosed by Systematic Spectroscopy
Abstract
We present the results from follow-up spectroscopy of three protocluster candidates at z∼3, selected as overdense regions of U-dropout galaxies in the wide-field imaging of the Hyper SuprimeCam Subaru Strategic Programme. All three targets exhibit tight clustering in three-dimensional space, i.e. on the sky (>4σ overdensity) and in redshift (>98.4% confidence), making for clear evidence of genuine protoclusters. Since these three protoclusters are identified by the same dataset and technique, they represent a good sample to study the diversity of protocluster properties with minimal observational biases. Although the average population across the three protoclusters is consistent with field galaxies, each protocluster individually exhibits distinguishing properties from each other or from field galaxies. In one protocluster, member galaxies stand out by a higher Lyα equivalent width (EW0), and massive members that are still highly star-forming. In contrast, relatively more suppressed star formation appears in another protocluster where the Lyα EW0 of member galaxies is systematically lower. These variations can be attributed to differences in the developmental phase of protoclusters. If the presence of quenching galaxies indicates a more mature system, galaxies with stronger Lyα emissions may be more prevalent in the earlier stages of cluster formation. The uniform approach to searching protoclusters on which this study builds enables us to link observed variations at the onset of cosmic noon to different pathways in the history of cluster formation.
Related
- Diverse Metallicities in Protoclusters at z ∼ 3.4 detected by Deep Learning
- Diverse Metallicities in Protoclusters at z ~ 3.4 detected by Deep Learning
- Probing faint radio activity from cores to filaments in two z=2.24 protoclusters with uGMRT
- Exploring the active galactic nucleus population in protoclusters: Results from the TNG300 simulation and comparison with observations
- Galaxy protoclusters as drivers of cosmic reionization. II. Te-based metallicities of Lyman-α emitters
BibTeX
@misc{toshikawa2026diverse,
title = {{Diverse Protoclusters at $z\sim3$ Disclosed by Systematic Spectroscopy}},
author = {Jun Toshikawa and Kentaro Koretomo and Nobunari Kashikawa and Stijn Wuyts and Marcin Sawicki and Malcolm N. Bremer and Yoshiaki Ono and Mariko Kubo and Tomoki Saito},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.01816},
eprint = {2610.01816},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.01816},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Diverse Protoclusters at z∼3 Disclosed by Systematic Spectroscopy
AU - Jun Toshikawa
AU - Kentaro Koretomo
AU - Nobunari Kashikawa
AU - Stijn Wuyts
AU - Marcin Sawicki
AU - Malcolm N. Bremer
AU - Yoshiaki Ono
AU - Mariko Kubo
AU - Tomoki Saito
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.01816
UR - https://arxiv.org/abs/2610.01816
AB - We present the results from follow-up spectroscopy of three protocluster candidates at z∼3, selected as overdense regions of U-dropout galaxies in the wide-field imaging of the Hyper SuprimeCam Subaru Strategic Programme. All three targets exhibit tight clustering in three-dimensional space, i.e. on the sky (>4σ overdensity) and in redshift (>98.4% confidence), making for clear evidence of genuine protoclusters. Since these three protoclusters are identified by the same dataset and technique, they represent a good sample to study the diversity of protocluster properties with minimal observational biases. Although the average population across the three protoclusters is consistent with field galaxies, each protocluster individually exhibits distinguishing properties from each other or from field galaxies. In one protocluster, member galaxies stand out by a higher Lyα equivalent width (EW_0), and massive members that are still highly star-forming. In contrast, relatively more suppressed star formation appears in another protocluster where the Lyα EW_0 of member galaxies is systematically lower. These variations can be attributed to differences in the developmental phase of protoclusters. If the presence of quenching galaxies indicates a more mature system, galaxies with stronger Lyα emissions may be more prevalent in the earlier stages of cluster formation. The uniform approach to searching protoclusters on which this study builds enables us to link observed variations at the onset of cosmic noon to different pathways in the history of cluster formation.
ER -