How the bar properties affect the induced spiral structure

TL;DR

This study uses numerical simulations to investigate how different properties of galactic bars influence the formation and characteristics of spiral structures in disc galaxies.

Contribution

It systematically explores the impact of bar length, shape, mass, and rotation rate on spiral arms across various galaxy rotation curves.

Findings

Spiral pitch angle correlates with bar pattern speed.

Spiral amplitude correlates with bar quadrupole moment.

Declining rotation curve galaxies form more prominent grand design spirals.

Abstract

Stellar bars and spiral arms co-exist and co-evolve in most disc galaxies in the local Universe. However, the physical nature of this interaction remains a matter of debate. In this work, we present a set of numerical simulations based on isolated galactic models aimed to explore how the bar properties affect the induced spiral structure. We cover a large combination of bar properties, including the bar length, axial ratio, mass and rotation rate. We use three galactic models describing galaxies with rising, flat and declining rotation curves. We found that the pitch angle best correlates with the bar pattern speed and the spiral amplitude with the bar quadrupole moment. Our results suggest that galaxies with declining rotation curves are the most efficient forming grand design spiral structure, evidenced by spirals with larger amplitude and pitch angle. We also test the effects of the velocity ellipsoid in a subset of simulations. We found that as we increase the radial anisotropy, spirals increase their pitch angle but become less coherent with smaller amplitude.