Gaia DR2 proper motions of dwarf galaxies within 420 kpc

By T. Fritz, G. Battaglia, M. Pawlowski, N. Kallivayalil, R. P. van der Marel, S. Sohn, C. Brook, G. Besla. Astronomy & Astrophysics, 2018

200 citations recorded by the source corpus.

A proper understanding of the Milky Way (MW) dwarf galaxies in a cosmological context requires knowledge of their 3D velocities and orbits. However, proper motion (PM) measurements have generally been of limited accuracy and are available only for more massive dwarfs. We therefore present a new study of the kinematics of the MW dwarf galaxies. We use the Gaia DR2 for those dwarfs that have been spectroscopically observed in the literature. We derive systemic PMs for 39 galaxies and galaxy candidates out to 420 kpc, and generally find good consistency for the subset with measurements available from other studies. We derive the implied Galactocentric velocities, and calculate orbits in canonical MW halo potentials of low (0.8 × 1012 M⊙) and high mass (1.6 × 1012 M⊙). Comparison of the distributions of orbital apocenters and 3D velocities to the halo virial radius and escape velocity, respectively, suggests that the satellite kinematics are best explained in the high-mass halo. Tuc III, Crater II, and additional candidates have orbital pericenters small enough to imply significant tidal influences. Relevant to the missing satellite problem, the fact that fewer galaxies are observed to be near apocenter than near pericenter implies that there must be a population of distant dwarf galaxies yet to be discovered. Of the 39 dwarfs: 12 have orbital poles that do not align with the MW plane of satellites (given reasonable assumptions about its intrinsic thickness); 10 have insufficient PM accuracy to establish whether they align; and 17 satellites align, of which 11 are co-orbiting and (somewhat surprisingly, in view of prior knowledge) 6 are counter-orbiting. Group infall might have contributed to this, but no definitive association is found for the members of the Crater-Leo group.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9bcda92a1aa758e6d0810398eda770690fe1e9a7

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Citations in the corpus

The milky way total mass profile as inferred from Gaia DR2 (2019, background): “…2012; Wang et al. 2012; Cautun et al. 2014a; Hellwing et al. 2016) while the radial mass profile plays a key role in determining the orbits of satellite galaxies and tidal streams (e.g. Barber et al. 2014; Monachesi et al. 2019a; Fritz et al. 2018; Cautun et al. 2019; Garavito-Camargo et al. 2019).”
Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived fromGaiaDR2 data (2018, background): “…of astrophysics, like stellar astrophysics (Gaia Collaboration et al. 2018a), the study of the dynamics of the Milky Way and other nearby galaxies ⋆ E-mail: h.baumgardt@uq.edu.au (e.g. Fritz et al. 2018) and even the study of massive black holes in the distant universe (e.g. Wolf et al. 2018).”
The total mass of the Large Magellanic Cloud from its perturbation on the Orphan stream (2018, background): “…are natural candidates since they have had closer passages with the LMC. Tucana III is an especially good candidate given its close passage with the LMC (Erkal et al. 2018; Simon 2018; Fritz et al. 2018), as are the 11 streams recently discovered in the Dark Energy Survey (Shipp et al. 2018).”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, background): “Indeed, the orbit inferred from Gaia DR2 proper motions of Crater 2 is consistent with rperi 10 kpc (see e.g. Fritz et al. 2018), compatible with significant mass-loss.”