Global stability of self-gravitating disks in modified gravity

Abstract

We study the global stability of a self-gravitating disk in the context of Modified Gravity (MOG) using N-body simulations. This theory is a relativistic scalar-tensor-vector theory of gravity and presented to address the dark matter problem. In the weak field limit MOG possesses two free parameters $\alpha$ and ${\mu }_0$ which have been already determined using rotation curve data of spiral galaxies. The evolution of a stellar self-gravitating disk and more specifically the bar instability in MOG is investigated and compared to a Newtonian case. Our models have exponential and Mestel-like surface densities as $\Sigma \propto \exp (-r/h)$ and $\Sigma \propto 1/r$. It is found out that, surprisingly, the disks are more stable against the bar mode in MOG than in Newtonian gravity. In other words, the bar growth rate is effectively slower than the Newtonian disks. Also we show that both free parameters, i.e. $\alpha$ and ${\mu }_0$, have stabilizing effects. In other words, increase in these parameters will decrease the bar growth rate.

16 pages, a reference added, few typos fixed, accepted version in MNRAS

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• Stellar Bar evolution in the absence of dark matter halo
• Structure of the equivalent Newtonian systems in MOND N-body simulations. Density profiles and the core-cusp problem
• Local Stability of Galactic Discs in Modified Dynamics
• Dynamics of Dwarf Galaxies in Scalar-Tensor-Vector-Gravity
• The Weak Lensing Mass of Cosmic Web Filaments and Modified Gravity (MOG)