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The kinematics of Galactic disc white dwarfs in Gaia DR2

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Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Early online date21 Jan 2019
DOIs
Publication statusE-pub ahead of print - 21 Jan 2019

Abstract

We present an analysis of the kinematics of Galactic disc white dwarf stars in the Solar
neighbourhood using data from Gaia Data Release 2. Selection of white dwarfs based on
parallax provides the first large, kinematically unbiased sample of Solar neighbourhood white
dwarfs to date. Various classical properties of the Solar neighbourhood kinematics have been
detected for the first time in the WD population.
The disc white dwarf population exhibits a correlation between absolute magnitude and
mean age, which we exploit to obtain an independent estimate of the Solar motion with respect
to the Local Standard of Rest. This is found to be ¹U;V;Wº = ¹9:5 1:2; 7:5 1:2; 8:2 1:2º
kms􀀀1. The UW components agree with studies based on main sequence stars, however the V
component differs and may be affected by systematics arising from metallicity gradients in the
disc. The velocity ellipsoid is shown to vary strongly with magnitude, and exhibits a significant
vertex deviation in the UV plane of around 15 degrees, due to the non-axisymmetric Galactic
potential.
The results of this study provide an important input to proper motion surveys for white
dwarfs, which require knowledge of the velocity distribution in order to correct for missing
low velocity stars that are culled from the sample to reduce subdwarf contamination.

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