Updated Proper Motions for Local Group Dwarf Galaxies Using Gaia Early Data Release 3

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 and the methodology is essentially unchanged from the original paper. The superiority of Gaia EDR3 compared to Gaia Data Release 2 means that Boötes 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.

BALRoGO: Bayesian Astrometric Likelihood Recovery of Galactic Objects – Global properties of over one hundred globular clusters with Gaia EDR3

“…In addition to the comparison between GCs made above, our proper motion fits of dSphs provide a very good agreement with the estimates from McConnachie & Venn (2020a), with differences 0.05 mas yr −1 for all of our fits in Table C1. In the very late stages of this work, Li et al (2021) also provided bulk proper motion fits 6 for 46 dSphs, presenting a very good overall agreement with our measurements, a part from the Bootes I dSph, for which our measurements are closer to those from McConnachie & Venn (2020a). This gives us confidence on the use of a non-Gaussian mixture in our Bayesian fit, along with the choice of a Pearson VII non-symmetric distribution of proper motions for interlopers, even though we neglected the convolution of the field stars component with Gaussian errors, after cleaning the data.…”

“…Comparisons between our method and previous works such as Baumgardt et al (2019), Vasiliev (2019a, McConnachie & Venn (2020a) and Vasiliev & Baumgardt (2021) indicate strong agreement of bulk proper motions for globular clusters and dwarf spheroidal galaxies, and of scale radii for globular clusters. In addition, we make available our measurements of center, bulk proper motions and scale radii for over a hundred globular clusters from the NGC catalog, along with a few dwarf spheroidal galaxies in Table C1 (see data availability section).…”

“…These two components present two clumps of data in proper motion space which allow one to assign membership probabilities to each clump. Vasiliev (2019a) and McConnachie & Venn (2020a) used Bayesian approaches based on Gaussian mixture models (a Gaussian distribution for both cluster and interloper clumps), while the original work from Gaia Collaboration et al (2018) used an iterative method based on clustering approaches and Baumgardt et al (2019) performed an iterative cleaning routine based on an 𝑛 − 𝜎 outlier rejection. Even though Bayesian approaches tend to be more reliable, the use of Gaussian mixtures must, however, be taken with caution, since the distribution of field stars has often much wider wings than a Gaussian distribution (it can be cleverly bypassed by assigning multiple Gaussians to the interloper component, such as in Vasiliev & Baumgardt 2021).…”

Phase-Space Correlations among Systems of Satellite Galaxies

“…Using data release 2 (DR2), the proper motions for 39 MW satellites were measured, many of them for the first time [43,44]. Additional satellite proper motions have been obtained since [45][46][47][48] and the recent Gaia EDR3 has allowed the previous measurements to be updated, resulting in a typical improvement in accuracy by a factor of 2.5 [49][50][51]. The future end-of-mission data release 4 is expected to further improve this accuracy.…”

“…This is in line with the general trend in cosmological simulations that contain massive baryonic host galaxies in their centers, indicating that tidal disruption in the central regions might play a role by preferentially destroying satellites on radial orbits. The now available Gaia EDR3 proper motion measurements [49][50][51], as well as future data releases, will help to clarify the situation. However, the issue might also be related to another peculiarity in the orbital distribution of satellite galaxies: their preference to lie close to the pericenter.…”