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

TL;DR

BALRoGO is a new Bayesian method and open-source software for accurately measuring centers, sizes, and motions of Milky Way globular clusters and dwarf spheroidals using Gaia EDR3 data, even with interloper contamination.

Contribution

It introduces innovative surface density and proper motion fitting techniques, including non-parametric CMD modeling, for robust analysis of stellar systems amidst field star contamination.

Findings

Successfully applied to Gaia EDR3 data for over 100 globular clusters and 9 dwarf spheroidals.

Provides consistent measurements of positions, sizes, and motions compared to previous studies.

Validated robustness through comparisons with literature and mock N-body data.

Abstract

We present BALRoGO: Bayesian Astrometric Likelihood Recovery of Galactic Objects, a public code to measure the centers, effective radii, and bulk proper motions of Milky Way globular clusters and Local Group dwarf spheroidals, whose data are mixed with Milky Way field stars. Our approach presents innovative methods such as surface density fits allowing for strong interloper contamination and proper motion fits using a Pearson VII distribution for interlopers, instead of classic Gaussian-mixture recipes. We also use non-parametric approaches to represent the color-magnitude diagram of such stellar systems based in their membership probabilities, previously derived from surface density and proper motion fits. The robustness of our method is verified by comparing its results with previous estimates from the literature as well as by testing it on mock data from N-body simulations. We applied BALRoGO to Gaia EDR3 data for over one hundred Milky Way globular clusters and nine Local Group dwarf spheroidals, and we provide positions, effective radii, and bulk proper motions. Finally, we make our algorithm available as an open source software.