摘要：We present new radial velocity (RV) measurements for 11 candidate young very-low-mass stars and brown dwarfs, with spectral types from M7 to L7. Candidate young objects were identified by features indicative of low surface gravity in their optical and/or near-infrared spectra. RV measurements are derived from high-resolution (R= λ/Δλ=20,000)J-band spectra taken with NIRSPEC at the Keck Observatory. We combine RVs with proper motions and trigonometric distances to calculate three-dimensional space positions and motions and to evaluate membership probabilities for nearby young moving groups (NYMGs). We propose 2MASSJ00452143+1634446 (L2β, J=13.06) as an RV standard given the precision and stability of measurements from three different studies. We test the precision and accuracy of our RV measurements as a function of spectral type of the comparison object, finding that RV results are essentially indistinguishable even with differences of ±5 spectral subtypes. We also investigate the strengths of gravity-sensitive K I lines at 1.24–1.25μm and evaluate their consistency with other age indicators. We confirm or reconfirm four brown dwarf members of NYMGs—2MASSJ00452143+1634446, WISEJ00470038+6803543, 2MASSJ011747483403258, and 2MASSJ193555952846343—and their previous age estimates. We identify one new brown dwarf member of the Carina-Near moving group, 2M2154−10. The remaining objects do not appear to be members of any known NYMGs, despite their spectral signatures of youth. These results add to the growing number of very-low-mass objects exhibiting signatures of youth that lack likely membership in a known NYMG, thereby compounding the mystery regarding local, low-density star formation.
