A Probabilistic Gaia DR3 Catalogue of Stars with Very Low Galactic Rest-Frame Speeds
Abstract
We present a Gaia DR3 catalogue of stars selected by very low Galactic rest-frame speed, VGRF < 25 km s−1. Using Lindegren et al. (2021) parallax zero-point corrections, Bailer-Jones et al. (2021) photogeometric distances, and Monte Carlo propagation of the Gaia parallax–proper-motion covariance, we identify a headline Tier A+B sample of 517 stars with P(VGRF < 25 km s−1) > 0.84 and a broader Tier A+B+C sample of 1,835 stars with P > 0.50. Orbit integrations in the static, axisymmetrized Hunter et al. (2024) Galactic potential map the broader sample onto compact, highly radial model orbits, with median eccentricity 0.949, median pericentre 151 pc, and median apocentre 7.45 kpc after 5,000-realisation orbit Monte Carlo propagation. A velocity-stratified matched-control comparison shows that the low-VGRF catalogue is the compact-pericentre endpoint of a smooth trend across the observed Gaia DR3 6D velocity distribution, rather than a distinct physical boundary at exactly 25 km s−1. Selection-function weights imply a larger effective count but are sensitive to sparse colour–magnitude cells, and external spectroscopy is available for only a small subset. We therefore present the catalogue as a probabilistic kinematic sample with model-dependent orbit diagnostics and subset-qualified chemical context, not as a complete census or population-membership decomposition.
