Signatures of the Galactic bar in high-order moments of proper motions measured by Gaia

Abstract

Our location in the Milky Way provides an exceptional opportunity to gain insight on the galactic evolution processes, and complement the information inferred from observations of external galaxies. Since the Milky Way is a barred galaxy, the study of motions of individual stars in the bulge and disc is useful to understand the role of the bar. The Gaia mission enables such study by providing the most precise parallaxes and proper motions to date. In this theoretical work, we explore the effects of the bar on the distribution of higher-order moments --the skewness and kurtosis-- of the proper motions by confronting two simulated galaxies, one with a bar and one nearly axisymmetric, with observations from the latest Gaia data release (GaiaDR2). We introduce the code ASGAIA to account for observational errors of Gaia in the kinematical structures predicted by the numerical models. As a result, we find clear imprints of the bar in the skewness distribution of the longitudinal proper motion ${\mu }_{\ell }$ in GaiaDR2, as well as other features predicted for the next Gaia data releases.

11 pages, 9 figures, accepted in A&A

References in corpus (12)

• The Gaia mission
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Modelling the Galactic bar using OGLE-II Red Clump Giant Stars
• Estimating distances from parallaxes. II. Performance of Bayesian distance estimators on a Gaia-like catalogue
• Kinematic modelling of the Milky Way using the RAVE and GCS stellar surveys
• New Constraints on the Galactic Bar
• Proper Motion Dispersions of Red Clump Giants in the Galactic Bulge: Observations and Model Comparisons
• The X-Shaped Milky Way Bulge in OGLE-III Photometry and in N-Body Models
• The Hercules stream as seen by APOGEE-2 South
• Kinematics in the Galactic Bulge with APOGEE: II. High-Order Kinematical Moments and Comparison to Extragalactic Bar Diagnostics
• The stellar kinematics of co-rotating spiral arms in Gaia mock observations
• Galactic Orbits of Globular Clusters in the Region of the Galactic Bulge

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