Hot Molecular Hydrogen in Galaxies at Redshift ~ 0.2-1.5 Revealed by JWST
Abstract
Molecular hydrogen (H2) is the fundamental component of the molecular gas reservoir that fuels star formation and black hole growth. While prominent hot H2 emission (≳ 1000 K) has been explored in nearby galaxies, its excitation mechanisms at higher redshifts remain poorly constrained. We present a systematic study of hot molecular gas traced via ro-vibrational H2 emitters at z~0.2-1.5 using JWST slitless spectroscopy. Exploiting JWST's great sensitivity to near-infrared H2 ro-vibrational transitions such as H2 1-0 S(1), we build a sample of 144 H2-luminous galaxies and characterize their multi-wavelength properties. About 96.5% and 80% of these galaxies are detected in the radio and far-infrared (FIR) bands, respectively, and their hot H2 emission strongly correlates with the radio and FIR radiation. Based on radio excess, X-ray emission, and optical diagnostics, 62 sources (43%) exhibit significant AGN activity. The H2 line luminosities of the sample show a sublinear dependence on radio luminosity, while the relation between the H2 luminosities and total infrared luminosities is approximately linear after excluding the radio-excess sources. These scaling relations suggest that star formation provides a baseline contribution to hot H2 excitation, while radio-excess sources require an additional contribution from AGN-related processes such as jet- or wind-driven shocks. These results reveal a multi-channel excitation scenario and shed new light on the interplay between star formation, AGN activity, and the interstellar medium during galaxy evolution.
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BibTeX
@misc{chen2026molecular,
title = {{Hot Molecular Hydrogen in Galaxies at Redshift ~ 0.2-1.5 Revealed by JWST}},
author = {Jie Chen and Linhua Jiang and Shuqi Fu and Zijian Zhang and Danyang Jiang and Jing Wang and Ran Wang and Darshan Kakkad},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.19319},
eprint = {2610.19319},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.19319},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Hot Molecular Hydrogen in Galaxies at Redshift ~ 0.2-1.5 Revealed by JWST
AU - Jie Chen
AU - Linhua Jiang
AU - Shuqi Fu
AU - Zijian Zhang
AU - Danyang Jiang
AU - Jing Wang
AU - Ran Wang
AU - Darshan Kakkad
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.19319
UR - https://arxiv.org/abs/2610.19319
AB - Molecular hydrogen (H_2) is the fundamental component of the molecular gas reservoir that fuels star formation and black hole growth. While prominent hot H_2 emission (≳ 1000 K) has been explored in nearby galaxies, its excitation mechanisms at higher redshifts remain poorly constrained. We present a systematic study of hot molecular gas traced via ro-vibrational H_2 emitters at z~0.2-1.5 using JWST slitless spectroscopy. Exploiting JWST's great sensitivity to near-infrared H_2 ro-vibrational transitions such as H_2 1-0 S(1), we build a sample of 144 H_2-luminous galaxies and characterize their multi-wavelength properties. About 96.5% and 80% of these galaxies are detected in the radio and far-infrared (FIR) bands, respectively, and their hot H_2 emission strongly correlates with the radio and FIR radiation. Based on radio excess, X-ray emission, and optical diagnostics, 62 sources (43%) exhibit significant AGN activity. The H_2 line luminosities of the sample show a sublinear dependence on radio luminosity, while the relation between the H_2 luminosities and total infrared luminosities is approximately linear after excluding the radio-excess sources. These scaling relations suggest that star formation provides a baseline contribution to hot H_2 excitation, while radio-excess sources require an additional contribution from AGN-related processes such as jet- or wind-driven shocks. These results reveal a multi-channel excitation scenario and shed new light on the interplay between star formation, AGN activity, and the interstellar medium during galaxy evolution.
ER -