Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud

Abstract

Aims. We perform a comprehensive determination of the systemic proper motions of 74 dwarf galaxies and dwarf galaxy candidates in the Local Group based on Gaia early data release 3. The outputs of the analysis for each galaxy, including probabilities of membership, will be made publicly available. The analysis is augmented by a determination of the orbital properties of galaxies within 500 kpc. Methods. We adopt a flexible Bayesian methodology presented in the literature, which takes into account the location of the stars on the sky, on the colour-magnitude diagram, and on the proper motion plane. We applied some modifications, in particular to the way the colour-magnitude diagram and spectroscopic information are factored in, for example, by including stars in several evolution phases. The bulk motions were integrated in three gravitational potentials: two where the Milky Way was treated in isolation and has a mass 0.9 & 1.6 × 1012 M⊙, and a time-varying potential, which includes the infall of a massive Large Magellanic Cloud (LMC). Results. We were able to determine bulk proper motions for 73 systems, and we consider 66 to be reliable measurements. For the first time, systemic motions are presented for galaxies out to a distance of 1.4 Mpc in the NGC 3109 association. The inclusion of the infall of a massive LMC significantly modifies the orbital trajectories of the objects, with respect to orbit integration in static Milky-Way-only potentials, and this leads to six galaxies likely being associated with the LMC, three possibly being associated with it, and one recently captured object. We discuss the results of the orbit integration in the context of the relation of the galaxies to the system of Milky Way satellites, implications for the too-big-to-fail problem, the impact on star formation histories, and tidal disruption.

Proper Motions, Orbits, and Tidal Influences of Milky Way Dwarf Spheroidal Galaxies

“…The Vast Polar Orbital structure and orbital poles alignment may be caused by the LMC (Garavito-Camargo et al 2021) but Pawlowski et al (2021) show the magnitude of the LMC perturbation is to small to fully explain the Vast Polar Orbital structure. Overall, we find excellent agreement between our results and other Gaia EDR3 proper motion results 3 (Mc-Connachie & Venn 2020b; Li et al 2021;Martínez-García et al 2021;Vitral 2021;Battaglia et al 2022;Qi et al 2022). In particular, McConnachie & Venn (2020b); Battaglia et al (2022) apply similar mixture models based on spatial position and proper motion with an additional color-magnitude component based on Gaia photometry.…”

“…Overall, we find excellent agreement between our results and other Gaia EDR3 proper motion results 3 (Mc-Connachie & Venn 2020b; Li et al 2021;Martínez-García et al 2021;Vitral 2021;Battaglia et al 2022;Qi et al 2022). In particular, McConnachie & Venn (2020b); Battaglia et al (2022) apply similar mixture models based on spatial position and proper motion with an additional color-magnitude component based on Gaia photometry. Similar to with Gaia DR2 data, we advocate for the use of auxiliary photometry especially for faint stars to assist with the identification of dSph members but acknowledge that the addition of a color-magnitude likelihood term is valuable to identify dSph stars.…”

“…This is due to both the reduced statistic errors with an additional year of data and the reduction of the systematic errors by roughly a factor of two relative to DR2. As a result, the orbital properties have improved (Li et al 2021;Battaglia et al 2022) and the internal rotation has been observed in a few dSphs with Gaia EDR3 data (Martínez-García et al 2021).…”

“…With Gaia EDR3 the systemic proper motions of the dSphs have significantly improved (e.g. McConnachie & Venn 2020b;Li et al 2021;Martínez-García et al 2021;Vitral 2021;Battaglia et al 2022). This is due to both the reduced statistic errors with an additional year of data and the reduction of the systematic errors by roughly a factor of two relative to DR2.…”

Live Fast, Die $α$-Enhanced: The Mass-Metallicity-$α$ Relation of the Milky Way's Disrupted Dwarf Galaxies

“…UMin was likely accreted at z ≈ 2 (Fillingham et al 2019) and quenched shortly after by e.g., ram pressure stripping. Its circular orbit (e ≈ 0.4 − 0.5, Fritz et al 2018;Li et al 2021;Battaglia et al 2022) and low mass relative to the other disrupted dwarfs may have kept it from being disrupted, since these properties prolong the dynamical friction timescale (e.g., Amorisco 2017;Naidu et al 2021;Vasiliev et al 2022). We also make note of Crater 2 and Antlia 2, which lie on the disrupted dwarf MZR and have the highest ∆[Fe/H] (0.34, 0.28) after UMin (0.36).…”