Detection of a dearth of stars with zero angular momentum in the solar neighbourhood

Abstract

We report on the detection in the combined $Gaia$-DR1/RAVE data of a lack of disk stars in the solar neighbourhood with velocities close to zero angular momentum. We propose that this may be caused by the scattering of stars with very low angular momentum onto chaotic, halo-type orbits when they pass through the Galactic nucleus. We model the effect in a Milky-Way like potential and fit the resulting model directly to the data, finding a likelihood ($\sim 2.7\sigma$) of a dip in the distribution. Using this effect, we can make a dynamical measurement of the Solar rotation velocity around the Galactic center: $v_{\odot }=239\pm 9$ km s${}^{-1}$. Combined with the measured proper motion of Sgr A${}^{\ast }$, this measurement gives a measurement of the distance to the Galactic centre: $R_0=7.9\pm 0.3$ kpc.

5 pages, 4 figures, submitted to ApJL

References in corpus (5)

• galpy: A Python Library for Galactic Dynamics
• The Radial Velocity Experiment (RAVE): first data release
• The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data
• The power spectrum of the Milky Way: Velocity fluctuations in the Galactic disk
• Overview and stellar statistics of the expected Gaia Catalogue using the Gaia Object Generator

Cited by in corpus (5)

• Carbon isotopic fractionation in molecular clouds
• Stars with fast Galactic rotation observed in Gaia TGAS: a signature driven by the Perseus arm?
• Searching for Stars Closely Encountering with the Solar System Based on Data from the Gaia DR1 and RAVE5 Catalogues
• On the origin of extreme trans-Neptunian objects within Modified Newtonian Dynamics
• The Galactic Pizza: Flat Rotation Curves in the Context of Cosmological Time-Energy Coupling