University of Hertfordshire

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From the same journal

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  • 1807.06486

    Accepted author manuscript, 1 MB, PDF-document

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Original languageEnglish
Article numberstz442
Number of pages12
Pages (from-to)2312–2323
JournalMonthly Notices of the Royal Astronomical Society
Journal publication date1 May 2019
Volume485
Issue2
Early online date13 Feb 2019
DOIs
Publication statusPublished - 1 May 2019

Abstract

A and F stars can be used as probes of outer Galactic disc kinematics: here we extend the work of Harris et al. by cross-matching their A/F sample with Gaia DR2 to bring in proper motions. These are combined with the already measured radial velocities and spectrophotometric distances to obtain full space motions. We use this sample of 1173 stars, located in two pencil-beam sightlines (ℓ = 178° and ℓ = 118°), to sample the Galactocentric velocity field out to almost RG = 15 kpc. We find there are significant differences in all three (radial, azimuthal, and vertical) kinematic components between the two directions. The rotation curve is roughly flat in the anticentre direction, confirming and extending the result of Kawata et al. thanks to the greater reach of our spectrophotometric distance scale. However at ℓ = 118° the circular velocity rises outwards from RG = 10.5 kpc and there is a more pronounced gradient in radial motion than is seen at ℓ = 178°. Furthermore, the A star radial motion differs from the F stars by ∼10 km s−1. We discuss our findings in the context of perturbers potentially responsible for the trends, such as the central bar, spiral arms, the warp, and external satellites. Our results at ℓ = 178° are broadly consistent with previous work on K giants in the anticentre, but the kinematics at ℓ = 118° in the Perseus region do not yet reconcile easily with bar or spiral arm perturbation.

Notes

© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.

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