# Effects of galaxy--satellite interactions on bar formation

## TL;DR

This study uses high-resolution simulations to show that low-mass satellite galaxy encounters can significantly delay or advance bar formation in Milky Way-like galaxies, with effects depending on satellite mass and orbit.

## Contribution

It demonstrates how satellite interactions influence bar formation timing without affecting the final bar structure, highlighting the indirect role of low-mass satellites.

## Key findings

- Satellite encounters can delay or advance bar formation by up to 1 Gyr.
- Final bar properties are unaffected by satellite interactions.
- Low-mass satellites below 10^9 M_sun have minimal impact unless very close.

## Abstract

Aims. We aim to show how encounters with low-mass satellite galaxies may alter the bar formation in a Milky Way-like disc galaxy. Methods. We use high-resolution N-body simulations of a disc galaxy prone to mild bar instability. For realistic initial conditions of satellites, we take advantage of cosmological simulations of Milky Way-like dark matter haloes. Results. The satellites may have a significant impact on the time of bar formation. Some runs with satellites demonstrate a delay, while others show an advancement in bar formation compared to the isolated run, with such time differences reaching $\sim$ 1 Gyr. Meanwhile, the final bar configuration, including its very appearance and the bar characteristics such as the pattern speed and the exponential growth rate of its amplitude are independent of the number of encounters and their orbits. The contribution of satellites with masses below $10^9 M_{\odot}$ is insignificant, unless their pericentre distances are small. We suggest that the encounters act indirectly via inducing perturbations across the disc that evolve to delayed waves in the central part and interfere with an emerging seed bar. The predicted effect for the present-day host galaxy is expected to be even more significant at redshifts $z \gtrsim 0.5$.