Résumé / Abstract Journal-club_Galaxies

Journal-club Galaxies

« An analytical derivation of the response of the Milky Way halo to the infall of the Large Magellanic Cloud »

Simon Rozier
Obs. Strasbourg (Strasbourg, France)

The Large Magellanic Cloud (LMC) is believed to be the largest satellite infalling the Milky Way (MW). Currently about its peri-centric passage, it has a strong influence on the stellar and dark matter halos of the galaxy, deflecting the orbits by its gravity. An accurate modelling of the deviations created by the LMC will help us setting multiple constraints on the physics of the merger, from the characteristics of the LMC (mass, orbit) to those of the MW stellar halo (density and stellar kinematics), through those of the MW dark matter halo (density and dark matter kinematics). While most of the community uses N-body simulations to study this problem, I will introduce an analytical formalism based on the matrix method of linear response theory. This method has two main advantages: (i) it is much more computationally efficient than simulations, so that we can explore a significant parameter space with different characteristics of the merger; (ii) its fundamental components are the stellar orbits in the MW mean field, leading to interpretations of the phenomena in terms of interacting orbits and resonant effects. I will show that the method leads to the same results as the latest simulations in terms of the density variations in the MW created by the LMC (the MW's response). I will then show that different anisotropies in the MW stellar halo lead to different morphologies of the MW response in stellar density, so that measurements of stellar densities will put a new constraint on the stellar halo's velocity anisotropy. Finally, I will show that the response's self-gravity is weak and dominated by the forced response, because of the young age of the merger. There is therefore little hope for constraining the dark matter halo kinematics with observations of the stellar halo.
jeudi 21 octobre 2021 - 11:30
Salle des séminaires Évry Schatzman, Institut d'Astrophysique
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