JADES: Dynamical Measurements of Dark Matter Halo Masses at z ≈ 7 Using Galaxy Pairs
Abstract
We present dynamical measurements of dark matter halo masses at z≈7 using galaxy pairs. Galaxy pairs in the early Universe are usually in their first infall, before substantial orbital evolution or phase mixing. Their relative velocities closely trace the halo mass, especially when the pair separation is near the halo virial radius. In the TNG100 simulation, we find that dynamical mass estimators can recover halo masses with an intrinsic scatter of ∼0.2 dex. We apply this method to 10 pair systems at z=6-8 with [O III] spectroscopy from the JWST Advanced Deep Extragalactic Survey (JADES). We infer the stellar-to-halo mass relation while marginalizing over projection effects, measurement uncertainties, and intrinsic scatter. We find a mean halo mass of log (M200/M⊙)=11.06±0.21 at log (M*/M⊙)=9. These galaxies do not appear to inhabit unusually massive halos. Our results instead indicate a high stellar-to-halo mass ratio, corresponding to an integrated star formation efficiency of 5+3−2%, about twice the TNG100 prediction, although the current statistical significance is limited. Future observations with larger samples will tighten these constraints and directly examine whether enhanced star formation efficiency drives the overabundance of luminous galaxies at cosmic dawn.
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BibTeX
@misc{wu2026jades,
title = {{JADES: Dynamical Measurements of Dark Matter Halo Masses at $z \approx 7$ Using Galaxy Pairs}},
author = {Zihao Wu and Daniel J. Eisenstein and Benjamin D. Johnson and Lars Hernquist and Sandro Tacchella and Brant E. Robertson and Santiago Arribas and Andrew J. Bunker and Qiao Duan and Jakob M. Helton and Zhiyuan Ji and Dávid Puskás and Pierluigi Rinaldi and Fengwu Sun and Hannah Übler and Yongda Zhu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.17756},
eprint = {2609.17756},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.17756},
}
RIS
TY - UNPB
TI - JADES: Dynamical Measurements of Dark Matter Halo Masses at z ≈ 7 Using Galaxy Pairs
AU - Zihao Wu
AU - Daniel J. Eisenstein
AU - Benjamin D. Johnson
AU - Lars Hernquist
AU - Sandro Tacchella
AU - Brant E. Robertson
AU - Santiago Arribas
AU - Andrew J. Bunker
AU - Qiao Duan
AU - Jakob M. Helton
AU - Zhiyuan Ji
AU - Dávid Puskás
AU - Pierluigi Rinaldi
AU - Fengwu Sun
AU - Hannah Übler
AU - Yongda Zhu
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2609.17756
UR - https://arxiv.org/abs/2609.17756
AB - We present dynamical measurements of dark matter halo masses at z≈7 using galaxy pairs. Galaxy pairs in the early Universe are usually in their first infall, before substantial orbital evolution or phase mixing. Their relative velocities closely trace the halo mass, especially when the pair separation is near the halo virial radius. In the TNG100 simulation, we find that dynamical mass estimators can recover halo masses with an intrinsic scatter of ∼0.2 dex. We apply this method to 10 pair systems at z=6-8 with [O III] spectroscopy from the JWST Advanced Deep Extragalactic Survey (JADES). We infer the stellar-to-halo mass relation while marginalizing over projection effects, measurement uncertainties, and intrinsic scatter. We find a mean halo mass of log (M_200/M_⊙)=11.06±0.21 at log (M_*/M_⊙)=9. These galaxies do not appear to inhabit unusually massive halos. Our results instead indicate a high stellar-to-halo mass ratio, corresponding to an integrated star formation efficiency of 5^+3_−2%, about twice the TNG100 prediction, although the current statistical significance is limited. Future observations with larger samples will tighten these constraints and directly examine whether enhanced star formation efficiency drives the overabundance of luminous galaxies at cosmic dawn.
ER -