Reconstructing the orbits of Milky Way dwarf galaxies: A Large Magellanic Cloud perspective

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Abstract
The orbital histories of the dwarf satellites of the Milky Way (MW) are key to understanding their evolution and placing their present-day properties in a dynamical context. We present the results of the orbit integration of 72 dwarfs in the vicinity of the MW, based on accurate 6D phase-space coordinates from the literature and a suite of six realistic, time-evolving gravitational potentials that account for the mutual interaction of the MW and the Large Magellanic Cloud (LMC). We provide the largest catalogue of orbital parameters for MW dwarfs to date, in terms of both galaxy sample size and the range of potentials explored. We also assess the binding status of the dwarfs and estimate their infall times, finding that the majority of them have spent the last 5 Gyr within the MW virial radius. From the reconstructed orbits, we identify ten likely LMC satellites, several of which have experienced very close passages within the LMC stellar disc. For the Small Magellanic Cloud (SMC), we find that its most recent pericentre about the LMC (∼8 kpc, ∼170 Myr ago) is consistent with predictions from the direct collision scenario proposed to explain the LMC’s offset and tilted bar. We also note a broad temporal coincidence between previous SMC pericentres and star formation rate peaks reported in both Magellanic Clouds, suggesting a causal connection. Finally, we identify Grus II and Tucana IV as possible MW satellites recently captured by the LMC, based on their pronounced orbital deflections and velocities relative to the LMC.
Funding Information
  • National Science Centre of Poland (2025/57/B/ST9/00321)
  • Ministerio de Ciencia, Innovación y Universidades (CEX2021-001131-S)
  • Ministerio de Ciencia, Innovación y Universidades (PID2024-155572NB-C22)
  • Ministerio de Ciencia, Innovación y Universidades (RYC2022-038448-I)
  • Ministerio de Ciencia, Innovación y Universidades (PID2023- 150319NB-C21/10.13039/501100011033)
  • Ministerio de Ciencia, Innovación y Universidades (PID2023-150319NB-C2)
  • Ministerio de Ciencia, Innovación y Universidades (RYC2024-051016-I)
  • Ministerio de Ciencia, Innovación y Universidades (RYC2022-035838-I)
  • Ministerio de Ciencia, Innovación y Universidades (PID2021-128131NB-I0)
  • Ministerio de Ciencia, Innovación y Universidades (RYC2022-037011-I)
  • Ministerio de Ciencia, Innovación y Universidades (RYC2023- 044924-I)
  • Ministerio de Ciencia, Innovación y Universidades (PID2024-162148NA-I00)
  • Ministerio de Ciencia, Innovación y Universidades (PID2024-155572NB-C21)
  • Ministerio de Ciencia, Innovación y Universidades (PID2024-155572NB- C22)
  • Ministerio de Ciencia, Innovación y Universidades (PID2021-124918NB-C41)
  • Royal Society (NIF\R1\241973)

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