Metal-poor Brown Dwarf Kinematics from JWST NIRSpec Spectroscopy
17 affiliations
- 1Northwestern University
- 2University of California San Diego
- 3United States Naval Observatory
- 4Stanford University
- 5NSF National Optical-Infrared Astronomy Research Laboratory
- 6Center for Astrophysics ∣ Harvard & Smithsonian
- 7Radcliffe Institute for Advanced Study at Harvard University
- 8Planétarium de Montréal
- 9Université de Montréal
- 10Instituto de Astrofísica de Canarias (IAC)
- 11Universidad de La Laguna (ULL)
- 12Nanjing University
- 13Department of Astrophysics
- 14San Francisco State University
- 15The University of Western Ontario
- 16University of Toledo
- 17University of Notre Dame
Abstract
Galactic archaeology relies on stellar kinematics and chemical abundances to identify various stellar populations and associations. With JWST, Galactic archaeology of ancient metal-poor brown dwarfs is now possible through high-sensitivity, medium-resolution spectroscopy. We present the first metal-poor brown dwarf radial velocity (RV) survey using JWST/NIRSpec G395H spectra ( λ /Δ λ ∼ 3000) for a sample of 23 LTY dwarfs across a wide range of temperatures and metallicities. We introduce a forward-modeling framework to measure robust RVs for brown dwarfs by focusing on the CO fundamental band at ∼4.5 μ m. By comparing to sources with existing high-resolution RV measurements, we demonstrate that G395H RVs can achieve a systematic uncertainty of 5 km s ⁻¹ , sufficient to examine their Galactic space motions. We identify kinematic members of the Milky Way’s thin disk, thick disk, and halo populations in this sample. We also confirm WISE J155349.98+693355.2 as likely associated with the Gaia–Enceladus merger remnant, and 2MASS J05325346+8246465 is likely associated with the Thamnos stream. Our study systematically demonstrates that JWST G395H spectroscopy can provide robust RVs in addition to detailed chemical abundances, necessary for Galactic archaeology studies. Future discoveries and characterization of brown dwarfs associated with Galactic halo substructures and streams will enable a stringent test of stellar/substellar formation and evolutionary models for diverse metallicities.
Versions
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BibTeX
@article{hsu2026metalpoor,
title = {{Metal-poor Brown Dwarf Kinematics from JWST NIRSpec Spectroscopy}},
author = {Chih-Chun Hsu and Christopher A. Theissen and Adam J. Burgasser and Adam C. Schneider and Christian Aganze and Aaron M. Meisner and Jonathan Gagné and Nicolas Lodieu and ZengHua Zhang and Genaro Suárez and Eileen C. Gonzales and Jacqueline K. Faherty and Jason J. 劲飞 Wang 王 and Stanimir A. Metchev and Dan Caselden and Michael C. Cushing and Roman Gerasimov},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aeac53},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aeac53},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Metal-poor Brown Dwarf Kinematics from JWST NIRSpec Spectroscopy
AU - Chih-Chun Hsu
AU - Christopher A. Theissen
AU - Adam J. Burgasser
AU - Adam C. Schneider
AU - Christian Aganze
AU - Aaron M. Meisner
AU - Jonathan Gagné
AU - Nicolas Lodieu
AU - ZengHua Zhang
AU - Genaro Suárez
AU - Eileen C. Gonzales
AU - Jacqueline K. Faherty
AU - Jason J. 劲飞 Wang 王
AU - Stanimir A. Metchev
AU - Dan Caselden
AU - Michael C. Cushing
AU - Roman Gerasimov
PY - 2026
DA - 2026/10/28
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aeac53
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aeac53
AB - Galactic archaeology relies on stellar kinematics and chemical abundances to identify various stellar populations and associations. With JWST, Galactic archaeology of ancient metal-poor brown dwarfs is now possible through high-sensitivity, medium-resolution spectroscopy. We present the first metal-poor brown dwarf radial velocity (RV) survey using JWST/NIRSpec G395H spectra ( λ /Δ λ ∼ 3000) for a sample of 23 LTY dwarfs across a wide range of temperatures and metallicities. We introduce a forward-modeling framework to measure robust RVs for brown dwarfs by focusing on the CO fundamental band at ∼4.5 μ m. By comparing to sources with existing high-resolution RV measurements, we demonstrate that G395H RVs can achieve a systematic uncertainty of 5 km s ⁻¹ , sufficient to examine their Galactic space motions. We identify kinematic members of the Milky Way’s thin disk, thick disk, and halo populations in this sample. We also confirm WISE J155349.98+693355.2 as likely associated with the Gaia–Enceladus merger remnant, and 2MASS J05325346+8246465 is likely associated with the Thamnos stream. Our study systematically demonstrates that JWST G395H spectroscopy can provide robust RVs in addition to detailed chemical abundances, necessary for Galactic archaeology studies. Future discoveries and characterization of brown dwarfs associated with Galactic halo substructures and streams will enable a stringent test of stellar/substellar formation and evolutionary models for diverse metallicities.
SN - 1538-4357
SN - 0004-637X
ER -