# Merger of galactic cores made of ultralight bosonic dark matter

## TL;DR

This paper investigates the dynamics of binary mergers of ultralight bosonic dark matter cores, revealing complex oscillatory behaviors and non-stationary final states through numerical simulations of the Gross-Pitaevskii-Poisson system.

## Contribution

It provides a detailed analysis of the merger process, including gravitational cooling and oscillation characteristics, which were not previously comprehensively studied for ultralight bosonic dark matter cores.

## Key findings

- Final configurations oscillate around a virialized state.
- Oscillation amplitude and frequency depend linearly on impact parameter.
- Mergers do not lead to a clear stationary state, even after relaxation.

## Abstract

We study binary mergers of ultralight bosonic dark matter cores by solving the Gross-Pitaevskii-Poisson system of equations. The analysis centers on the dynamics of the relaxation process and the behavior of the configuration resulting from the merger, including the Gravitational Cooling with its corresponding emission of mass and angular momentum. The oscillations of density and size of the final configuration are characterized, indicating that for the equal mass case the dependency of the amplitude and frequency of these oscillations on the impact parameter of the pre-merger configuration is linear. The amplitude of these oscillations changes by a factor of two or more indicating the final configuration does not approach a clear stationary state even though it oscillates around a virialized state. For the unequal mass case, global quantities also indicate the final configuration oscillates around a virialized state, although the density does not show a dominant oscillation mode. The evolution of the angular momentum prior and post merger is analyzed in all cases.