Detection of a radial velocity gradient in the extended local disc with RAVE

A. Siebert*, B. Famaey, I. Minchev, G. M. Seabroke, J. Binney, B. Burnett, K. C. Freeman, M. Williams, O. Bienaymé, J. Bland-Hawthorn, R. Campbell, J. P. Fulbright, B. K. Gibson, G. Gilmore, E. K. Grebel, A. Helmi, U. Munari, J. F. Navarro, Q. A. Parker, W. A. Reid & 5 others A. Siviero, M. Steinmetz, F. Watson, R. F.G. Wyse, T. Zwitter

*Corresponding author for this work

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Abstract

Using a sample of 213713 stars from the Radial Velocity Experiment (RAVE) survey, limited to a distance of 2kpc from the Sun and to |z| < 1kpc, we report the detection of a velocity gradient of disc stars in the fourth quadrant, directed radially from the Galactic Centre. In the direction of the Galactic Centre, we apply a simple method independent of stellar proper motions and of Galactic parameters to assess the existence of this gradient in the RAVE data. This velocity gradient corresponds to |K+C| > rsim 3 km s-1 kpc-1, where K and C are the Oort constants measuring the local divergence and radial shear of the velocity field, respectively. In order to illustrate the effect, assuming a zero radial velocity of the local standard of rest we then reconstruct the two-dimensional Galactocentric velocity maps using two different sets of proper motions and photometric distances based either on isochrone fitting or on K-band magnitudes, and considering two sets of values for the Galactocentric radius of the Sun and local circular speed. Further observational confirmation of our finding with line-of-sight velocities of stars at low latitudes, together with further modelling, should help constrain the non-axisymmetric components of the Galactic potential, including the bar, the spiral arms and possibly the ellipticity of the dark halo.

Original languageEnglish
Pages (from-to)2026-2032
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Volume412
Issue number3
DOIs
Publication statusPublished - Apr 2011

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    Siebert, A., Famaey, B., Minchev, I., Seabroke, G. M., Binney, J., Burnett, B., ... Zwitter, T. (2011). Detection of a radial velocity gradient in the extended local disc with RAVE. Monthly Notices of the Royal Astronomical Society, 412(3), 2026-2032. https://doi.org/10.1111/j.1365-2966.2010.18037.x