![]() Currently, no model available can explain the entirety of the data in this area of the sky. According to our analysis, these two structures show very similar but clearly distinct kinematic trends, which can be summarized as follows: the amplitude of the velocity variation in vϕ and vz in the ACS is higher compared to the Ring, whose velocity gradients appear to be flatter. The stellar overdensity in the anti-centre region can be split into two components, the narrow, stream-like ACS and the smooth Ring. ![]() Additionally, both vertical and azimuthal components of their motion are shown to vary considerably but gradually as a function of Galactic longitude and latitude. We demonstrate that Monoceros members rotate around the Galaxy with azimuthal speeds of ∼230 km s−1, only slightly lower than that of the Sun. ![]() We use recalibrated SDSS astrometry in combination with positions from Gaia DR1 to provide tangential motion measurements with a systematic uncertainty <5 km s−1 for the Main Sequence stars at the distance of the Monoceros Ring. We present the first detailed study of the behaviour of the stellar proper motion across the entire Galactic anticentre area visible in the Sloan Digital Sky Survey (SDSS) data.
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