Boltzmann-Poisson-like approach to simulating the galactic halo response to satellite accretion Dependence on the halo density profile

TL;DR

This paper presents a collisionless Boltzmann equation-based method to simulate galactic halo responses to satellite accretion, revealing how different density profiles influence response modes and halo dynamics with lower computational costs than traditional N-body simulations.

Contribution

It introduces a novel CBE+Poisson solver for simulating halo responses, demonstrating its effectiveness and efficiency in capturing complex dynamical features and dependence on density profiles.

Findings

The method captures local wake and global density responses.

The response modes are sensitive to the halo density profile.

Cored profiles show richer response modes and induce cylindrical rotation.

Abstract

Recent studies have reported the detection of the galactic stellar halo wake and dipole triggered by the Large Magellanic Cloud (LMC), mirroring the corresponding response from dark matter (DM). These studies open up the possibility of adding constraints on the global mass distribution of the Milky Way (MW), and even on the nature of DM itself, with current and upcoming stellar surveys reigniting the discussion on response modes in dynamical friction. However, the simulation of such features remains computationally challenging. We used a collisionless Boltzmann equation (CBE)+Poisson solver based on an existing method from the literature. We investigated the density and velocity response modes in simulations of Galactic-type DM halos accreting LMC-sized satellites, including the dependence on the halo density profile. We successfully captured both the local wake and the global over- and underdensity induced in the host halo. We also captured the velocity response. In line with previous studies, we find that the code can reproduce the core formation in the cuspy profile and the satellite core stalling. The angular power spectrum (APS) response is shown to be sensitive to each density profile. The cored Plummer density profile seems the most responsive, displaying a richness of modes. At the end of the simulation, the central halo acquires cylindrical rotation. The CBE description makes it tenable to capture the response modes with a better handling of noise in comparison to traditional N-body simulations. Hence, given a certain noise level, BPM has a lower computational cost than N-body simulations, making it feasible to explore large parameter sets. We anticipate that stellar spheroids in the MW or external galaxies could show central cylindrical rotation if they underwent a massive accretion event. The code can be adjusted to include a variety of DM physics.