Metal-poor Brown Dwarf Kinematics from JWST NIRSpec Spectroscopy

@misc{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. Wang and Stanimir Metchev and Dan Caselden and Michael C. Cushing and Roman Gerasimov},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.28746},
  eprint = {2609.28746},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.28746},
  note = {CC BY 4.0},
}

TY  - UNPB
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. Wang
AU  - Stanimir Metchev
AU  - Dan Caselden
AU  - Michael C. Cushing
AU  - Roman Gerasimov
PY  - 2026
DA  - 2026/09/26
PB  - arXiv
DO  - 10.48550/arxiv.2609.28746
UR  - https://arxiv.org/abs/2609.28746
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/Δλ∼ 3,000) 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 μm. 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.
ER  -