The Connection between Orbits and Isophotal Shape in Elliptical Galaxies

TL;DR

This study investigates how the orbital composition of elliptical galaxy remnants influences their isophotal shapes, revealing that merger violence affects orbital types and that orbital content correlates with observed shapes and velocities.

Contribution

It demonstrates that disc mergers alone do not produce a clear boxy or disky shape dichotomy, highlighting the role of orbital content and merger violence in shaping elliptical galaxies.

Findings

Disc mergers do not produce a boxy-disky dichotomy.

Orbital shape varies with merger violence.

Orbital content correlates with isophotal shape and line-of-sight velocity.

Abstract

We examine the origin of photometrical properties of N-body merger remnants from the perpective of their orbital content. We show that disc mergers alone are unlikely to form a boxy-discy dichotomy in isophotal shape, because of the survival of disc-like orbits even in violent mergers. The shape of the different orbit families can vary strongly, depending on how violent the merger was. Minor axis tubes can become boxy and box orbits can be round. However, for edge-on projections isophotal shape, orbital content and line-of-sight velocity are well connected.