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27 April 2024 |
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Galactic kinematics and dynamics from RAVE stars | | James Binney
; Ben Burnett
; Georges Kordopatis
; Matthias Steinmetz
; Gerry Gilmore
; Olivier Bienayme
; Joss Bland-Hawthorn
; Benoit Famaey
; Eva K. Grebel
; Amina Helmi
; Julio Navarro
; Quentin Parker
; Warren A. Reid
; George Seabroke
; Fred Watson
; Mary E.K. Williams
; Rosie F.G. Wyse
; Tomaz Zwitter
; | | Date: |
17 Sep 2013 | | Abstract: | We analyse the kinematics of ~400000 RAVE stars. We split the sample into hot
and cold dwarfs, red-clump and non-clump giants. The kinematics of the clump
giants are consistent with being identical with those of non-clump giants. We
fit Gaussian velocity ellipsoids to the meridional-plane components of velocity
of each star class and give formulae from which the shape and orientation of
the velocity ellipsoid can be determined at any location. The data are
consistent with the giants and the cool dwarfs sharing the same velocity
ellipsoids; sigma_z rises from 21 kms in the plane to sim 55 kms at |z|=2 kpc,
while sigma_r rises from 37 kms to 82 kms. At (R,z) the longest axis of one of
these velocity ellipsoids is inclined to the Galactic plane by an angle ~0.8
arctan(z/R). We use a novel formula to obtain precise fits to the highly
non-Gaussian distributions of v_phi components.
We compare the observed velocity distributions with the predictions of a
dynamical model fitted to the velocities of stars that lie within ~150 pc of
the Sun and star counts towards the Galactic pole. The model accurately
reproduces the non-Gaussian nature of the v_r and v_z distributions and
provides excellent fits to the data for v_z at all locations. The model v_phi
distributions for the cool dwarfs fit the data extremely well, while those for
the hot dwarfs have displacements to low v_phi that grow with |z| from very
small values near the plane. At |z|>0.5 kpc, the theoretical v_phi
distributions for giants show a deficit of stars with large v_phi and the model
v_r distributions are too narrow. Systematically over-estimating distances by
20 per cent introduces asymmetry into the model v_r and v_z distributions near
the plane and but significantly improves the fits to the data at |z|>0.5 kpc.
The quality of the fits lends credence to the assumed, disc-dominated,
gravitational potential. | | Source: | arXiv, 1309.4285 | | Services: | Forum | Review | PDF | Favorites | |
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