A Caltech Library Service

The Brown Dwarf Kinematics Project (BDKP). V. Radial and Rotational Velocities of T Dwarfs from Keck/NIRSPEC High-resolution Spectroscopy

Hsu, Chih-Chun and Burgasser, Adam J. and Theissen, Christopher A. and Gelino, Christopher R. and Birky, Jessica L. and Diamant, Sharon J. M. and Bardalez Gagliuffi, Daniella C. and Aganze, Christian and Blake, Cullen H. and Faherty, Jacqueline K. (2021) The Brown Dwarf Kinematics Project (BDKP). V. Radial and Rotational Velocities of T Dwarfs from Keck/NIRSPEC High-resolution Spectroscopy. Astrophysical Journal Supplement Series, 257 (2). Art. No. 45. ISSN 0067-0049. doi:10.3847/1538-4365/ac1c7d.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We report multiepoch radial velocities, rotational velocities, and atmospheric parameters for 37 T-type brown dwarfs observed with Keck/NIRSPEC. Using a Markov Chain Monte Carlo forward-modeling method, we achieve median precisions of 0.5 and 0.9 km s⁻¹ for radial and rotational velocities, respectively. All of the T dwarfs in our sample are thin-disk brown dwarfs. We confirm previously reported moving group associations for four T dwarfs. However, the lack of spectral indicators of youth in two of these sources suggests that these are chance alignments. We confirm two previously unresolved binary candidates, the T0+T4.5 2MASS J11061197+2754225 and the L7+T3.5 2MASS J21265916+7617440, with orbital periods of 4 and 12 yr, respectively. We find a kinematic age of 3.5 ± 0.3 Gyr for local T dwarfs, consistent with nearby late M dwarfs (4.1 ± 0.3 Gyr). Removal of thick-disk L dwarfs in the local ultracool dwarf sample gives a similar age for L dwarfs (4.2 ± 0.3 Gyr), largely resolving the local L dwarf age anomaly. The kinematic ages of local late M, L, and T dwarfs can be accurately reproduced with population simulations incorporating standard assumptions of the mass function, star formation rate, and brown dwarf evolutionary models. A kinematic dispersion break is found at the L4–L6 subtypes, likely reflecting the terminus of the stellar main sequence. We provide a compilation of precise radial velocities for 172 late M, L, and T dwarfs within ∼20 pc of the Sun.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hsu, Chih-Chun0000-0002-5370-7494
Burgasser, Adam J.0000-0002-6523-9536
Theissen, Christopher A.0000-0002-9807-5435
Birky, Jessica L.0000-0002-7961-6881
Diamant, Sharon J. M.0000-0001-7398-7035
Bardalez Gagliuffi, Daniella C.0000-0001-8170-7072
Aganze, Christian0000-0003-2094-9128
Blake, Cullen H.0000-0002-6096-1749
Faherty, Jacqueline K.0000-0001-6251-0573
Additional Information:© 2021. The American Astronomical Society. Received 2021 April 8; revised 2021 August 3; accepted 2021 August 3; published 2021 November 29. The authors thank Maria Rosa Zapatero Osorio and Emily Rice for providing their NIRSPEC data obtained on 2000 June 15 and on 2005 July 19, respectively. The authors also thank Gregory Doppmann, Percy Gomez, Carlos Alvarez, and other Keck Observatory staff and support astronomers for their assistance in obtaining Keck/NIRSPEC observations. C.-C.H. and A.J.B. acknowledge funding support from the National Science Foundation under award No. AST-1517177. The material presented in this paper is based on work supported by the National Aeronautics and Space Administration under grant No. NNX15AI75G. Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51447.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. J.B. acknowledges support from National Science Foundation Graduate Research Fellowship Program grant DGE-1762114. This work utilizes the measurements from 2MASS catalogs and Gaia Data Release 2. The authors acknowledge the usefulness of the SIMBAD database and VizieR service. The authors thank the anonymous referee for his/her/their useful review that has improved the original manuscript. The 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. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has with the indigenous Hawaiian community, and that the W. M. Keck Observatory stands on Crown and Government Lands that the State of Hawai'i is obligated to protect and preserve for future generations of indigenous Hawaiians. Portions of this work were conducted at the University of California, San Diego, which was built on the unceded territory of the Kumeyaay Nation, whose people continue to maintain their political sovereignty and cultural traditions as vital members of the San Diego community. Facility: Keck: II (NIRSPEC). - Software: BANYAN Σ (Gagné et al. 2018c), Texmaker, Sublime Text, Python, NumPy (van der Walt et al. 2011), SciPy (Virtanen et al. 2020), Matplotlib (Hunter 2007), pandas (McKinney 2010), seaborn (Waskom & the seaborn development team 2020), Astropy (Astropy Collaboration et al. 2013), wavelets, SPLAT (Burgasser & Splat Development Team 2017), emcee (Foreman-Mackey et al. 2013), galpy (Bovy 2015).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51447.001-A
NSF Graduate Research FellowshipDGE-1762114
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Brown dwarfs; T dwarfs; Radial velocity; Stellar kinematics; Stellar dynamics
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Brown dwarfs (185); T dwarfs (1679); Radial velocity (1332); Stellar kinematics (1608); Stellar dynamics (1596)
Record Number:CaltechAUTHORS:20211207-393010000
Persistent URL:
Official Citation:Chih-Chun Hsu et al 2021 ApJS 257 45
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112246
Deposited By: George Porter
Deposited On:08 Dec 2021 17:26
Last Modified:01 Feb 2022 22:58

Repository Staff Only: item control page