Abstract
We use SEGUE and Hipparcos data to restrict the behaviour of the rotation curve of the Milky Way in the solar neighbourhood. Then we construct a density model of the Milky Way which best reproduces the available observations of the rotation curve and is consistent with the density constraints in the solar neighbourhood. This equation assumes constancy of the shape of the velocity ellipsoid, its alignment with the axes of spherical coordinate system, and an exponential disc with scalelength Rd and a constant thickness. Thus we find the circular velocity vc for our samples. We assume the local circular velocity vc� = 231km/s, the local standard of rest from (3), and the disc scalelength Rd = 2.5kpc. The resulting rotation curve is presented in the left panel of Fig. 1. SEGUE sample is plotted with purple line, GCS is separated in 5 colour bins, which are plotted with points of different colours. Mean rotational velocities without correction for asymmetric drift being implemented are plotted with dashed lines, the corrected circular velocity with solid lines. The consistency of the circular velocity for GCS colour bins with different mean velocities demonstrates viability of the adopted value of Rd and other our assumptions. The rotation curve for the SEGUE data appears to be essentially flat in the solar neighbourhood. At least, it obviously demonstrates no drastic dip between 8 and 10kpc, as it was assumed in (6).
Highlights
The rotation curve gives a powerful tool to study the mass distribution in the Milky Way
We use SEGUE and Hipparcos data to restrict the behaviour of the rotation curve of the Milky Way in the solar neighbourhood
We construct a density model of the Milky Way which best reproduces the available observations of the rotation curve and is consistent with the density constraints in the solar neighbourhood
Summary
The rotation curve gives a powerful tool to study the mass distribution in the Milky Way. An extensive compilation of observational data is given in [6]. The density model proposed in [6] is inconsistent with local density and dark matter density constraints in the solar neighbourhood [4]. We reanalyse these observational data, supplement them with local constraints and with our own analysis of the behaviuor of the rotation curve in the solar neighbourhood, and construct a density model of the Galaxy
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