Darwin Tames an Andromeda Dwarf: Unraveling the Orbit of NGC 205 Using a Genetic Algorithm
K. M. Howley, M. Geha, P. Guhathakurta, R. M. Montgomery, G. Laughlin,, and K. V. Johnston

TL;DR
This study uses a genetic algorithm combined with N-body simulations to determine the orbit and properties of NGC 205, revealing it is likely on its first passage around M31 with high tangential velocity.
Contribution
The paper introduces a novel approach combining genetic algorithms with restricted N-body simulations to constrain the orbit and progenitor properties of NGC 205.
Findings
NGC 205 is likely on its first passage around M31.
The satellite has a high tangential velocity of 300-500 km/s.
NGC 205's orbit places it significantly behind M31, with velocities near or exceeding escape velocity.
Abstract
NGC 205, a close satellite of the M31 galaxy, is our nearest example of a dwarf elliptical galaxy. Photometric and kinematic observations suggest that NGC 205 is undergoing tidal distortion from its interaction with M31. Despite earlier attempts, the orbit and progenitor properties of NGC 205 are not well known. We perform an optimized search for these unknowns by combining a genetic algorithm with restricted N-body simulations of the interaction. This approach, coupled with photometric and kinematic observations as constraints, allows for an effective exploration of the parameter space. We represent NGC 205 as a static Hernquist potential with embedded massless test particles that serve as tracers of surface brightness. We explore 3 distinct, initially stable configurations of test particles: cold rotating disk, warm rotating disk, and hot, pressure-supported spheroid. Each model…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Galaxies: Formation, Evolution, Phenomena · Astrophysics and Star Formation Studies
