Systematic Study of Gravitational Waves from Galaxy Merger

TL;DR

This study systematically investigates gravitational waves from galaxy mergers using N-body simulations, highlighting the dominant role of halo components and the effects of initial conditions on wave features.

Contribution

It provides new insights into how galaxy components and initial parameters influence gravitational wave emission during mergers.

Findings

Halo component dominates gravitational wave emission

Peak luminosity is around 10^31 erg/sec for large halo collisions

Luminosity scales approximately with the cube of galaxy mass

Abstract

A systematic study of gravitational waves from galaxy mergers, through N-body simulations, was performed. In particular, we investigated the relative importance of galaxy components (disk, bulge and halo) and effects of initial relative velocity, relative angular momentum and mass ratio of the galaxies. We found that the features of light curve of gravitational waves, such as peak width and luminosity, are reliably simulated with particle numbers larger than ~10^4. Dominant contribution to gravitational wave emission came from the halo component, while peak luminosity amounted to 10^31 erg/sec for the collision of two halos with mass 3.8 x10^12Msun/h. We also found that the initial relative velocity in the direction of the initial separation did not significantly affect gravitational wave emission, while the initial relative angular momentum broadened the peak width and suppressed the luminosity. Mass dependence of the peak luminosity was also investigated, and we obtained evidence that the luminosity is proportional to the cubic mass when the scaling relation is satisfied. This behavior was considered by a simple analysis.