Comparing radial migration in dark matter and MOND regimes

TL;DR

This study compares radial migration effects in Milky Way-like galaxies under dark matter and MOND gravity, revealing significantly more pronounced migration in the MOND regime through numerical simulations.

Contribution

It provides a quantitative comparison of stellar radial migration in DM and MOND regimes, highlighting the stronger migration effects in MOND.

Findings

Radial migration is up to five times more pronounced in MOND.

Most prominent resonances include co-rotation and Lindblad resonances.

MOND shows greater stellar displacement over 6 Gyr.

Abstract

Multiple studies on radial migration in disc galaxies have proven the importance of the effect of resonances with non-axisymmetric components on the evolution of galactic discs. However, the dynamical effects of classic Newtonian dynamics with dark matter (DM) differ from MOdified Newtonian Dynamics (MOND) and might trigger different radial migration. A thorough analysis of radial migration considering these two gravitational regimes might shed some light on different predictions of DM and MOND theories. We aim to quantitatively and qualitatively compare the effects of resonances and stellar radial migration (churning) in a Milky Way-like (MW-like) galaxy in the DM and MOND regimes. We performed simulations of a MW-like galaxy to analyse the effect of non-axisymmetric structures (galactic bar and spiral arms) considering various parameters of the spiral structure. We conducted a two-dimensional numerical simulation consisting of the integration of $2 \cdot 10^6$ stars in a static rotating galactic potential for $6~\mbox{Gyr}$. We analysed the change in the star's position, the guiding radius, as well as the frequency phase space. We investigated DM and MOND approaches. The outcome of the simulation shows that the radial migration is much more pronounced in the MOND regime compared to the DM one. Compared to the DM approach, in the MOND regime, we observe up to five times as many stars with a maximum change in the guiding radius of more than $1.5~\mbox{kpc}$ during the time interval from $2-6~\mbox{Gyr}$.Analysis of the frequency phase space reveals that the most prominent resonances in all DM and MOND configurations are the co-rotation resonance with the spiral arms ($m=p=1$), outer Lindblad resonance with the galactic bar and spiral arms, and the co-rotation resonance ($m=2$, $p=1$) with the superposition of the galactic bar and spiral arms, $2 \Omega = \Omega_b + \Omega_{sp}$.