H I Absorbers as Beacons of Hidden Structure at z ∼ 3: Multi-Component, Metal-Rich Absorption System near a Protocluster
Abstract
H I gas traces the large-scale structure and provides the primary fuel for star formation. High-z protoclusters are ideal laboratories to study how H I gas is accreted and consumed during the formation of the most massive structures in the Universe. However, much remains unknown about the distribution and physical state of their H I gas. We examine a rare configuration in which a protocluster candidate is located in front of a quasar at z=3.09. Our spectroscopic campaign confirms a protocluster at z=3.079: however, no corresponding strong H I absorption is found in the background quasar spectrum. Instead, we serendipitously discover a prominent H I absorption feature at z∼ 3.01, offset by ∼ 60 cMpc from the centre of the protocluster. Spanning an exceptionally broad velocity range of ∼ 2000 km s−1 (∼ 40 cMpc), this absorption is decoupled from the confirmed member galaxies. Detailed kinematic modelling reveals this absorption comprises five distinct components rather than a single cloud. Moreover, one of these components exhibits a super-solar metallicity ([O/H] = +1.19+0.91−0.78). We propose two physical scenarios for this unique system: (1) an additional, hidden massive protocluster along the line of sight, and/or (2) metal-rich outflows and metal-poor inflows driven by a single massive galaxy. The discovery highlights that while protoclusters are not universally associated with strong H I absorption, targeting the strong H I absorbers may serve as a beacon for uncovering massive, metal-rich protoclusters or complex gas kinematics in the early Universe.
Related
- Mathematical Framework for the Effects of Sample Absorption on Raman Intensity for Quantification and Detection Thresholds of Minerals in Two-Component Geological Mixtures.
- 1RXS J174320.1-042953: another polar with a red-shifted absorption component in emission line wings
- Listening to the Standard Candles: A Survey-Scale Search for Phase-Coded Beacons in Cepheids, RR~Lyrae and β~Cephei Stars
- The Milky Way's Early Disk Was Built in Bursts. II. The Multi-component Age-Metallicity Structure of the High-α Disk
- MusE GAs FLOw and Wind (MEGAFLOW) XIV: Background-Galaxy Absorption Reveals Kiloparsec-Scale Structure in the Cool Circumgalactic Medium
BibTeX
@misc{koretomo2026absorbers,
title = {{H I Absorbers as Beacons of Hidden Structure at $z \sim 3$: Multi-Component, Metal-Rich Absorption System near a Protocluster}},
author = {Kentaro Koretomo and Nobunari Kashikawa and Toru Misawa and Jun Toshikawa and Yoshihiro Takeda and Hisakazu Uchiyama and Junya Arita and Shunta Shimizu and Ryo Emori and Kei Ito and Satoshi Kikuta and Mariko Kubo and Yoshiaki Ono and Marcin Sawicki and Rhythm Shimakawa},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.04349},
eprint = {2609.04349},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.04349},
}
RIS
TY - UNPB
TI - H I Absorbers as Beacons of Hidden Structure at z ∼ 3: Multi-Component, Metal-Rich Absorption System near a Protocluster
AU - Kentaro Koretomo
AU - Nobunari Kashikawa
AU - Toru Misawa
AU - Jun Toshikawa
AU - Yoshihiro Takeda
AU - Hisakazu Uchiyama
AU - Junya Arita
AU - Shunta Shimizu
AU - Ryo Emori
AU - Kei Ito
AU - Satoshi Kikuta
AU - Mariko Kubo
AU - Yoshiaki Ono
AU - Marcin Sawicki
AU - Rhythm Shimakawa
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.04349
UR - https://arxiv.org/abs/2609.04349
AB - H I gas traces the large-scale structure and provides the primary fuel for star formation. High-z protoclusters are ideal laboratories to study how H I gas is accreted and consumed during the formation of the most massive structures in the Universe. However, much remains unknown about the distribution and physical state of their H I gas. We examine a rare configuration in which a protocluster candidate is located in front of a quasar at z=3.09. Our spectroscopic campaign confirms a protocluster at z=3.079: however, no corresponding strong H I absorption is found in the background quasar spectrum. Instead, we serendipitously discover a prominent H I absorption feature at z∼ 3.01, offset by ∼ 60 cMpc from the centre of the protocluster. Spanning an exceptionally broad velocity range of ∼ 2000 km s^−1 (∼ 40 cMpc), this absorption is decoupled from the confirmed member galaxies. Detailed kinematic modelling reveals this absorption comprises five distinct components rather than a single cloud. Moreover, one of these components exhibits a super-solar metallicity ([O/H] = +1.19^+0.91_−0.78). We propose two physical scenarios for this unique system: (1) an additional, hidden massive protocluster along the line of sight, and/or (2) metal-rich outflows and metal-poor inflows driven by a single massive galaxy. The discovery highlights that while protoclusters are not universally associated with strong H I absorption, targeting the strong H I absorbers may serve as a beacon for uncovering massive, metal-rich protoclusters or complex gas kinematics in the early Universe.
ER -