Formation of Transitional cE/UCD Galaxies through Massive/Dwarf Disc Galaxy Mergers

TL;DR

This paper investigates how mergers between dwarf disc galaxies and larger spiral galaxies can produce compact stellar remnants resembling cE or UCD galaxies, highlighting the stripping process and resulting properties.

Contribution

It presents detailed numerical models of dwarf-spiral galaxy mergers, demonstrating the formation of transitional cE/UCD objects with specific structural characteristics.

Findings

Remnants are compact with effective radii of 100-200 pc.

Remnants contain minimal gas and dark matter after merging.

The process involves stripping outer stellar layers during galaxy destruction.

Abstract

The dynamics of the merger of a dwarf disc galaxy with a massive spiral galaxy of the Milky Way type have been studied in detail. The remnant of such interaction after numerous crossings of the satellite through the disc of the main galaxy is a compact stellar core, the characteristics of which are close to small compact elliptical galaxies (cEs) or large ultra-compact dwarfs (UCDs). Such transitional cE/UCD objects with an effective radius of 100-200 pc arise as a result of stripping the outer layers of the stellar core during the destruction of a disc dwarf galaxy. Numerical models of the satellite before interaction include baryonic matter (stars and gas) and dark mass. We use N-body to describe the dynamics of stars and dark matter and Smoothed-Particle Hydrodynamics to model the gas components of both galaxies. The direct method of calculating the gravitational force between all particles provides a qualitative resolution of spatial structures up to 10 pc. The simulated cE/UCD galaxies contain very little gas and dark matter at the end of their evolution.