发表机构
Northwestern University; University of California San Diego; United States Naval Observatory, Flagstaff Station; Stanford University; NSF National Optical-Infrared Astronomy Research Laboratory; Radcliffe Institute for Advanced Study at Harvard University; Planétarium de Montréal, Espace pour la Vie（西北大学; 加州大学圣迭戈分校; 美国海军天文台弗拉格斯塔夫站; 斯坦福大学; 美国国家光学-红外天文研究实验室; 哈佛大学拉德克利夫高等研究院; 蒙特利尔天文馆，生命空间）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用JWST NIRSpec G395H光谱对23个金属贫乏褐矮星进行视向速度测量，通过前向建模实现5 km/s精度，识别出银盘和银晕成员，并确认与Gaia-Enceladus和Thamnos流相关，为银河考古学提供新工具。
AI 中文摘要
银河考古学依赖于恒星运动学和化学丰度来识别不同的恒星群体和关联。借助JWST，通过高灵敏度、中分辨率光谱，对古老金属贫乏褐矮星的银河考古学现在成为可能。我们首次利用JWST/NIRSpec G395H光谱（λ/Δλ ~ 3,000）对23个覆盖宽温度范围和金属丰度范围的LTY型褐矮星样本进行了金属贫乏褐矮星视向速度（RV）巡天。我们引入了一个前向建模框架，通过聚焦约4.5 μm的CO基频带，来测量褐矮星的稳健视向速度。通过与已有高分辨率视向速度测量的源进行比较，我们证明G395H视向速度可以实现5 km s⁻¹的系统不确定性，足以检验它们的银河空间运动。我们在该样本中识别出银河系薄盘、厚盘和晕族群体的运动学成员。我们还确认WISE J155349.98+693355.2很可能与Gaia-Enceladus并合遗迹相关，而2MASS J05325346+8246465很可能与Thamnos流相关。我们的研究系统地证明了JWST G395H光谱除了提供详细的化学丰度外，还能提供稳健的视向速度，这对于银河考古学研究是必需的。未来对与银河晕亚结构和流相关的褐矮星的发现和表征，将能够对不同金属丰度下的恒星/亚恒星形成和演化模型进行严格的检验。
英文摘要
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 ($λ/Δλ\sim$ 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 $\sim$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.
CommentsAccepted for publication in The Astrophysical Journal. 22 pages, 5 figures, 6 tables
