An updated detailed characterization of planes of satellites in the MW and M31

Abstract

We present a detailed characterization of planes of satellite galaxies in the Milky Way (MW) and M31. For a positional analysis, we introduce an extension to the `4-galaxy-normal density plot' method \citep[][P13]{Pawlowski13}. It finds the normal directions to the predominant planar configurations of satellites of a system, yielding for each a \textit{collection} of planes of increasing member satellites. This allows to quantify the quality of planes in terms of population ($N_{\mathrm{sat}}$) and spatial flattening ($c/a$). We apply this method to the latest data for confirmed MW and M31 satellite samples, with 46 and 34 satellites, respectively. New MW satellites form part of planes previously identified from the sample with $N_{\mathrm{sat}}=27$ studied in P13: we identify a new plane with $N_{\mathrm{sat}}=39$ as thin as the VPOS-3 ($c/a\sim 0.2$), and with roughly the same normal direction; so far the most populated plane that thin reported in the Local Group. We introduce a new method to determine, using kinematic data, the axis of maximum co-orbitation of MW satellites. Interestingly, this axis approximately coincides with the normal to the former plane: $\ge 45\pm 5\%$ of satellites co-orbit. In M31 we discover a plane with $N_{\mathrm{sat}}=18$ and $c/a\sim 0.15$, i.e., quality comparable to the GPoA, and perpendicular to it. This structure is viewed face-on from the Sun making it susceptible to M31 satellite distance uncertainties. An estimation of the perpendicular velocity dispersion suggests it is dynamically unstable. Finally we find that mass is not a property determining a satellite's membership to good quality planes.

20 pages. 13 figures. 5 tables. Accepted for publication in MNRAS. Supercedes arXiv:1908.02298. Please cite the NEW version. This updated and extended version of the paper considers up-to-date samples of confirmed MW and M31 satellite galaxies and studies the co-orbitation of MW satellites

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Cited by in corpus (11)

• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• The Hubble Space Telescope Survey of M31 Satellite Galaxies I. RR Lyrae-based Distances and Refined 3D Geometric Structure
• The Clustering of Orbital Poles Induced by the LMC: Hints for the Origin of Planes of Satellites
• 3D hydrodynamic simulations for the formation of the Local Group satellite planes
• Barred spiral galaxies in modified gravity theories
• Flattened structures of dwarf satellites around massive host galaxies in the MATLAS low-to-moderate density fields
• The spatial distribution of Milky Way satellites, gaps in streams and the nature of dark matter
• On the absence of backsplash analogues to NGC 3109 in the $\Lambda$CDM framework
• Planes of satellites around simulated disk galaxies II: Time-persistent planes of kinematically-coherent satellites in $\Lambda$CDM
• Analyzing Planar Galactic Halo Distributions with Fuzzy/Cold Dark Matter Models
• The Cen A galaxy group: dynamical mass and missing baryons