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The Brown Dwarf Kinematics Project I. Proper motions and tangential velocities for a large sample of late-type M, L, and T dwarfs

Faherty, Jacqueline K. and Burgasser, Adam J. and Cruz, Kelle L. and Shara, Michael M. and Walter, Frederick M. and Gelino, Christopher R. (2009) The Brown Dwarf Kinematics Project I. Proper motions and tangential velocities for a large sample of late-type M, L, and T dwarfs. Astronomical Journal, 137 (1). pp. 1-18. ISSN 0004-6256. doi:10.1088/0004-6256/137/1/1.

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We report proper-motion measurements for 427 late-type M, L, and T dwarfs, 332 of which have been measured for the first time. Combining these new proper motions with previously published measurements yields a sample of 841 M7-T8 dwarfs. We combined parallax measurements or calculated spectrophotometric distances, and computed tangential velocities for the entire sample. We find that kinematics for the full and volume-limited 20 pc samples are consistent with those expected for the Galactic thin disk, with no significant differences between late-type M, L, and T dwarfs. Applying an age-velocity relation we conclude that the average kinematic age of the 20 pc sample of ultracool dwarfs is older than recent kinematic estimates and more consistent with age results calculated with population synthesis models. There is a statistically distinct population of high tangential velocity sources (V tan > 100 km s^–1) whose kinematics suggest an even older population of ultracool dwarfs belonging to either the Galactic thick disk or halo. We isolate subsets of the entire sample, including low surface gravity dwarfs, unusually blue L dwarfs, and photometric outliers in J – Ks color and investigate their kinematics. We find that the spectroscopically distinct class of unusually blue L dwarfs has kinematics clearly consistent with old age, implying that high surface gravity and/or low metallicity may be relevant to their spectral properties. The low surface gravity dwarfs are kinematically younger than the overall population, and the kinematics of the red and blue ultracool dwarfs suggest ages that are younger and older than the full sample, respectively. We also present a reduced proper-motion diagram at 2MASS (Two Micron All Sky Survey) Ks for the entire population and find that a limit of HKs > 18 excludes M dwarfs from the L and T dwarf population regardless of near-infrared color, potentially enabling the identification of the coldest brown dwarfs in the absence of color information.

Item Type:Article
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URLURL TypeDescription
Faherty, Jacqueline K.0000-0001-6251-0573
Burgasser, Adam J.0000-0002-6523-9536
Cruz, Kelle L.0000-0002-1821-0650
Additional Information:© 2009 The American Astronomical Society. Received 2008 July 11, accepted for publication 2008 September 11. Published 2008 December 2. Print publication: Issue 1 (2009 January). We acknowledge receipt of observation time through the SMARTS (Small and Moderate Aperture Research Telescope System) consortium and MDM consortium. We especially thank the observing staff at CTIO, including J. Velazquez the night assistant for a week of CPAPIR observing time in 2008 January. Stony Brook's participation in the SMARTS consortium is made possible by generous support by the Dean of Arts and Sciences, the Provost, and the Vice-President for Research of Stony Brook University. J.F. would like to thank S. Lepine for his useful conversations about kinematic studies. We also thank R. Doyon, E. Artigau, and L. Malo for help with CPAPIR usage and data reduction and K. Schlesinger, R. Assef, and D. Atlee for help with using TIFKAM and the 1.3 m telescope at MDM. This research has benefited from the M, L, and T dwarf compendium housed at and maintained by Chris Gelino, Davy Kirkpatrick, and Adam Burgasser. This publication has made use of the Very Low Mass (VLM) Binaries Archive maintained by Nick Siegler at We have also made use of data products from the 2MASS, which is a joint project of the University of Massachusetts and the IPAC/Caltech, funded by NASA and the National Science Foundation. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, Caltech, under contract with NASA. [K.L.C. was a] Spitzer Postdoctoral Fellow. Online-only material: color figures, machine-readable and VO tables.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Stony Brook UniversityUNSPECIFIED
NASA Spitzer FellowshipUNSPECIFIED
Subject Keywords:astrometry; stars: fundamental parameters; stars: low-mass, brown dwarfs
Issue or Number:1
Record Number:CaltechAUTHORS:FAHaj09
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12514
Deposited By: Archive Administrator
Deposited On:12 Dec 2008 03:10
Last Modified:08 Nov 2021 22:29

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