M51 Revisited: A Genetic Algorithm Approach of Its Interaction History

Abstract

Detailed models of observed interacting galaxies suffer from the extended parameter space. Here, we present results from our code minga which couples an evolutionary optimization strategy (a genetic algorithm) with a fast N-body method. minga allows for an automatic search of the optimal region(s) in parameter space within a few hours to a few days of CPU time on a modern PC by investigating of the order of 10⁵ models. We demonstrate its applicability by modelling the Hi intensity and velocity maps of the interacting system M51 and NGC 5195. We get a good fit for the Hi intensity map and we can reproduce the counter-rotation feature of the Hi arm. Our result corroborates the results of Salo and Laurikainen (2000) who favour a model with multiple passages through M51’s disk.