Chemo-kinematics of the Gaia RR Lyrae: the halo and the disc

ABSTRACT We present the results of a multicomponent kinematic model of a large sample of RR Lyrae detected by Gaia. By imposing a fourfold symmetry and employing Gaia proper motions, we are able to infer the behaviour of the velocity ellipsoid between ≈3 and ≈30 kpc from the centre of the Galaxy. We...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2021-04, Vol.502 (4), p.5686-5710
Main Authors: Iorio, Giuliano, Belokurov, Vasily
Format: Article
Language:English
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Summary:ABSTRACT We present the results of a multicomponent kinematic model of a large sample of RR Lyrae detected by Gaia. By imposing a fourfold symmetry and employing Gaia proper motions, we are able to infer the behaviour of the velocity ellipsoid between ≈3 and ≈30 kpc from the centre of the Galaxy. We detect the presence of two distinct components: a dominant non-rotating halo-like population and a much smaller rotating disc-like population. We demonstrate that the halo RR Lyrae can be described as a superposition of an isotropic and radially biased parts. The radially biased portion of the halo is characterized by a high orbital anisotropy β ≈ 0.9 and contributes between 50 per cent and 80 per cent of the halo RR Lyrae at 5 < R(kpc)
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stab005