Radial Velocities, Space Motions, and Nearby Young Moving Group Memberships of Eleven Candidate Young Brown Dwarfs
Abstract
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 2MASS J00452143+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 1.24–1.25 μm and evaluate their consistency with other age indicators. We confirm or reconfirm four brown dwarf members of NYMGs—2MASS J00452143+1634446, WISE J00470038+6803543, 2MASS J011747483403258, and 2MASS J193555952846343—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.
Additional Information
© 2019 The American Astronomical Society. Received 2018 November 30; revised 2019 April 1; accepted 2019 April 13; published 2019 June 3. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to thank the staff of the Keck Observatory for their outstanding support, including Luca Rizzi, Jim Lyke, Cynthia Wilburn, Terry Stickel, Jason McIlroy, Heather Hershley, and Barbara Schaefer. Observing assistance from Kay Hiranaka was greatly appreciated. The authors are grateful for assistance with references from J.T. Wright and E.R. Newton via Twitter, and J. Gagne for help with the BANYAN II and BANYAN Σ codes. A.R.R., V.D., and E.L.R. were responsible for writing the majority of the paper. A.R.R. was responsible for the youth analysis, conclusions, and system notes. V.D. and E.A. were responsible for the NIRSPEC data reduction and description in the paper. V.D., E.L.R., E.A., and A.R.R. were responsible for the RV analysis. M.K.A. was responsible for the line measurements, and description of PHEW. K.L.C. was responsible for the spectral typing and advising of V.D. and E.A. J.K.F. was responsible for the general survey outline. This material is based upon work supported by the National Science Foundation under grant Nos. AST-1313278, AST-1313132, and AST-1153335. E.A. acknowledges support from the National Science Foundation Graduate Research Fellowship under grant No. DGE 1752814. This research was supported in part by NASA through the American Astronomical Society's Small Research Grant Program. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This publication makes use of data from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has benefited from the M, L, and T dwarf compendium housed at DwarfArchives.org and maintained by Chris Gelino, Davy Kirkpatrick, and Adam Burgasser. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France and NASA's Astrophysics Data System. The work of A.R.R. was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Keck telescope time was granted by NOAO, through the Telescope System Instrumentation Program (TSIP). TSIP is funded by NSF. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facility: Keck:II (NIRSPEC). -Attached Files
Published - Riedel_2019_AJ_157_247.pdf
Accepted Version - 1904.10579.pdf
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Additional details
- Eprint ID
- 96046
- Resolver ID
- CaltechAUTHORS:20190603-142357759
- W. M. Keck Foundation
- AST-1313278
- NSF
- AST-1313132
- NSF
- AST-1153335
- NSF
- DGE-1752814
- NSF Graduate Research Fellowship
- NASA/JPL/Caltech
- Created
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2019-06-03Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field