Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Space Velocities of L- and T-type Dwarfs   (Abridged) We have obtained radial velocities of a sample of 18 ultracool
dwarfs (M6.5-T8) using high-resolution, near-infrared spectra obtained with
NIRSPEC and the Keck II telescope. We have confirmed that the radial velocity
of Gl 570 D is coincident with that of the K-type primary star Gl 570 A, thus
providing additional support for their true companionship. The presence of
planetary-mass companions around 2MASS J05591914-1404488 (T4.5V) has been
analyzed using five NIRSPEC radial velocity measurements obtained over a period
of 4.37 yr. We have computed UVW space motions for a total of 21 L and T dwarfs
within 20 pc of the Sun. This population shows UVW velocities that nicely
overlap the typical kinematics of solar to M-type stars within the same spatial
volume. However, the mean Galactic (44.2 km/s) and tangential (36.5 km/s)
velocities of the L and T dwarfs appear to be smaller than those of G to M
stars. A significant fraction (~40%) of the L and T dwarfs lies near the Hyades
moving group (0.4-2 Gyr), which contrasts with the 10-12% found for
earlier-type stellar neighbors. Additionally, the distributions of all three
UVW components (sigma_{UVW} = 30.2, 16.5, 15.8 km/s) and the distributions of
the total Galactic (sigma_{v_tot} = 19.1 km/s) and tangential (sigma_{v_t} =
17.6 km/s) velocities derived for the L and T dwarf sample are narrower than
those measured for nearby G, K, and M-type stars, but similar to the
dispersions obtained for F stars. This suggests that, in the solar
neighborhood, the L- and T-type ultracool dwarfs in our sample (including brown
dwarfs) is kinematically younger than solar-type to early M stars with likely
ages in the interval 0.5-4 Gyr.

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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: math
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The categories of this paper are: adap-org