Local Group environment
The Milky Way's evolution is deeply influenced by its interactions with neighbouring systems, with the Large Magellanic Cloud (LMC) being the most significant perturbing power. Recent studies highlight that the LMC's near passage to our galaxy has left a pronounced imprint, particularly on the Milky Way's outer halo.
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We recently investigated the effect of the LMC's passage, focusing on its impact on the orbits of other satellite galaxies. These satellites, previously thought to follow relatively stable orbits, are now understood to have been dynamically altered by the LMC's gravitational influence. To do so, we have integrated the evolution of the entire MW, LMC and other MW satellites (including gravitational interaction and dynamical friction) backwards in time .... up to the point where the gravitational influence of the LMC is negligible. Next, we removed the mass from the LMC and integrated this system forward. This trick allows us to see directly which satellites are affected by the LMC by simply comparing their orbits with and without LMC.
The animations above illustrate the backward (left) and forward (right) integration. Among other effects, one can see how the bound group of satellites dispersed once the LMC mass was removed. On the right, both types of orbits of Milky Way satellites are shown at later stages of evolution.
The formation of the plane of satellites observed around several nearby galaxies is a genuinely intriguing phenomenon. Whether it challenges the ΛCDM model or not, it remains a fascinating subject of study. The arrangement of satellite galaxies into these thin, coherent structures is not only unexpected but also piques curiosity about the underlying mechanisms shaping such formations.
I study the HESTIA simulations of the Local Group, aiming to understand whether any coherent structures can appear as the result of major mergers. The animation on the right shows the evolution of all subhaloes that ended up inside the Milky Way analogue. The colour of the points highlights the subhaloes that are bound to the same halo before the merger with the Milky Way.
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The figure above shows the evolution of the velocity vectors of subhaloes in a major-merger group infall scenario. It suggests that major mergers deliver groups of subhaloes which retain their kinematic coherence for many Gyr after their group infall, similar to the planes of satellites... (work in progress)