JADES: Dynamical Measurements of Dark Matter Halo Masses at $z \approx 7$ Using Galaxy Pairs

Year: 2026

Type: preprint

Abstract: We present dynamical measurements of dark matter halo masses at $z\approx7$ 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 $\sim$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 $\log\,(M_{200}/M_\odot)=11.06\pm0.21$ at $\log\,(M_{*}/M_\odot)=9$. 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.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2609.17756

Authors: Wu, Zihao, Eisenstein, Daniel J., Johnson, Benjamin D., Hernquist, Lars, Tacchella, Sandro, Robertson, Brant E., Arribas, Santiago, Bunker, Andrew J., Duan, Qiao, Helton, Jakob M., Ji, Zhiyuan, Puskás, Dávid, Rinaldi, Pierluigi, Sun, Fengwu, Übler, Hannah, Zhu, Yongda

Institutions: Center for Astrophysics Harvard & Smithsonian, University of Cambridge, University of California, Santa Cruz, Centro de Astrobiología, University of Oxford, Pennsylvania State University, University of Arizona, The University of Texas at Austin, Westlake University, Max Planck Institute for Extraterrestrial Physics

Language: English

Topic: Galaxies: Formation, Evolution, Phenomena

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, National Aeronautics and Space Administration, University of California, Santa Cruz, Space Telescope Science Institute, UK Research and Innovation, European Commission, Max-Planck-Gesellschaft, Ministerio de Ciencia e Innovación, Science and Technology Facilities Council, Trinity College, University of Cambridge, Agencia Estatal de Investigación

OpenAlex ID: W7213516069