Updated proper motions for Local Group dwarf galaxies using Gaia Early Data Release 3

TL;DR

This paper provides updated systemic proper motion measurements for 58 Milky Way satellite galaxies using Gaia EDR3, improving accuracy and enabling first-time detections for some objects, thereby enhancing our understanding of their dynamics.

Contribution

It offers the first Gaia EDR3-based proper motion estimates for several dwarf galaxies and significantly reduces uncertainties compared to Gaia DR2.

Findings

First-time proper motion detections for Bo{"o}tes 4, Cetus 3, Pegasus 3, and Virgo 1.

Median uncertainties halved compared to Gaia DR2.

Systematic errors now dominate for 25 objects.

Abstract

Updated systemic proper motion estimates for 58 Milky Way satellite galaxies, based on Gaia Early Data Release 3 (EDR3), are provided. This sample is identical to that studied by McConnachie & Venn (2020) and the methodology is essentially unchanged from the original paper. The superiority of Gaia EDR3 compared to Gaia Data Release 2 means that Bo{\"o}tes 4, Cetus 3, Pegasus 3 and Virgo 1 have detectable systemic proper motions for the first time. For the entire galaxy sample, the median random uncertainties in the systemic proper motions are approximately a factor of two better than the previous estimates using Gaia DR2. Relevant systematic errors, which are also a factor of two smaller, dominate over random uncertainties for 25 out of the 58 objects in the sample.