RR Lyrae stars trace the Milky Way warp
Mauro Cabrera-Gadea, Cecilia Mateu, Pau Ramos

TL;DR
This study demonstrates that RR Lyrae stars in the Milky Way's thin disc trace the Galactic warp, revealing an intermediate-age stellar population's kinematic behavior and pattern speed, thus providing new insights into the warp's age dependence.
Contribution
First detection of the warp traced by thin disc RR Lyrae stars, linking stellar age to warp structure and dynamics in the Milky Way.
Findings
RR Lyrae stars trace the Galactic warp in the anticentre direction.
Warp pattern speed estimated at approximately 13 km/s/kpc.
Vertical velocity dispersion suggests an intermediate-age stellar population.
Abstract
The outskirts of the Milky Way disc have been known to be warped since the late 1950s. Although various stellar populations have shown an underlying warped distribution, the relation between the age of the population and the warp they trace remains an open question. Our goal in this work is to detect the presence of the warp in the RR Lyrae (RRL) population of the Galactic disc. We use a compilation of public catalogues of RRL stars, precise photometric distances () and Gaia DR3 proper motions to kinematically select a sample of thin disc RRL in the Galactic anticentre, where the tangential velocity best approximates the azimuthal velocity to differentiate between disc and halo. For disc-like RRL we analyse their mean vertical height and mean vertical velocity. We show, for the first time, that RRL stars with thin disc-like kinematics trace the warp. In the anticentre…
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Taxonomy
TopicsAstro and Planetary Science · Astronomy and Astrophysical Research · Stellar, planetary, and galactic studies
