Gaussian process model for the local stellar velocity field from Gaia data release 2. Issue 4 (14th September 2022)

• Record Type: Journal Article
• Authors: Nelson, Patrick; Widrow, Lawrence M
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 516:Issue 4(2022)
• Page Start: 5429
• Page End: 5439
• Publication Date: 2022-09-14
• Subjects: Galaxy: kinematics and dynamics -- Galaxy: structure -- solar neighborhood; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac2594
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We model the local stellar velocity field using position and velocity measurements for 4M stars from the second data release of Gaia . We determine the components of the mean or bulk velocity in $\sim 27\, 000$ spatially defined bins. Our assumption is that these quantities constitute a Gaussian process where the correlation between the bulk velocity at different locations is described by a simple covariance function or kernel. We use a sparse Gaussian process algorithm based on inducing points to construct a non-parametric, smooth, and differentiable model for the underlying mean stellar velocity field. We estimate the Oort constants A, B, C, and K and find values in excellent agreement with previous results. Maps of the velocity field within $2\, {\rm kpc}$ of the Sun reveal complicated substructures, which provide clear evidence that the local disc is in a state of disequilibrium. We present the first three-dimensional map of the divergence of the stellar velocity field and identify regions of the disc that may be undergoing compression and rarefaction.