Dynamical modelling of galactic disc outskirts

TL;DR

This paper reviews dynamical models of galactic disc outskirts, compares a merger remnant model with observations, and discusses how stellar age affects density profiles and break radii in galaxy discs.

Contribution

It introduces a model of galactic outer disc structure based on a major merger remnant and compares it with observational data.

Findings

Good agreement between the merger model and observed density profiles.

Younger stellar populations have flatter inner and steeper outer density profiles.

The break radius remains consistent across different stellar ages.

Abstract

I review briefly some dynamical models of structures in the outer parts of disc galaxies, including models of polar rings, tidal tails and bridges. I then discuss the density distribution in the outer parts of discs. For this, I compare observations to results of a model in which the disc galaxy is in fact the remnant of a major merger, and find good agreement. This comparison includes radial profiles of the projected surface density and of stellar age, as well as time evolution of the break radius and of the inner and outer disc scale lengths. I also compare the radial projected surface density profiles of dynamically motivated mono-age populations and find that, compared to older populations, younger ones have flatter density profiles in the inner region and steeper in the outer one. The break radius, however, does not vary with stellar age, again in good agreement with observations.