Journal Article

The properties of the local spiral arms from RAVE data: two-dimensional density wave approach

A. Siebert, B. Famaey, J. Binney, B. Burnett, C. Faure, I. Minchev, M. E. K. Williams, O. Bienaymé, J. Bland-Hawthorn, C. Boeche, B. K. Gibson, E. K. Grebel, A. Helmi, A. Just, U. Munari, J. F. Navarro, Q. A. Parker, W. A. Reid, G. Seabroke, A. Siviero, M. Steinmetz and T. Zwitter

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 425, issue 3, pages 2335-2342
Published in print September 2012 | ISSN: 0035-8711
Published online September 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21638.x
The properties of the local spiral arms from RAVE data: two-dimensional density wave approach

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Abstract

Using the Radial Velocity Experiment (RAVE) survey, we recently brought to light a gradient in the mean galactocentric radial velocity of stars in the extended solar neighbourhood. This gradient likely originates from non-axisymmetric perturbations of the potential, among which a perturbation by spiral arms is a possible explanation. Here, we apply the traditional density wave theory and analytically model the radial component of the two-dimensional velocity field. Provided that the radial velocity gradient is caused by relatively long-lived spiral arms that can affect stars substantially above the plane, this analytic model provides new independent estimates for the parameters of the Milky Way spiral structure. Our analysis favours a two-armed perturbation with the Sun close to the inner ultra-harmonic 4:1 resonance, with a pattern speed and a small amplitude per cent of the background potential (14 per cent of the background density). This model can serve as a basis for numerical simulations in three dimensions, additionally including a possible influence of the Galactic bar and/or other non-axisymmetric modes.

Keywords: stars: kinematics and dynamics; Galaxy: fundamental parameters; Galaxy: kinematics and dynamics

Journal Article.  5541 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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