Amy L. Hewitt

Hi! I’m an Astrophysics PhD student at the University of Lancaster, working on detecting gravitational waves from pulsars.

1 minute read

Modelling interacting galaxies

This project aimed to model a new system of interacting galaxies by writing a suitable N-body code in Python. This model would then be analysed and compared to observed features in the galaxy system. Two codes were written, one using a Barnes-Hut algorithm to model galaxies containing live Navarro–Frenk–White (NFW) dark matter halos, and another to simulate them using NFW halo potentials and a model for dynamical friction. The Arp 240 system was modelled and a best fit interaction was found with a pericentre of 37.7 kpc, 0.22 Gyrs ago which was in agreement with expected and literature values. A visual comparison between the simulation and observations showed many similarities, such as a spiral structure, bar, counterarms, and a tail. However, more detailed comparisons between the two codes and the literature found inconsistencies, such as a line of sight velocity 28.3 times larger than observed, so the reliability of the simulations is questioned.

The project was my first experience using Python and I taught myself throughout the duration. This was made easier by my previous education in C as part of my course. I worked with two other students on this project with each of us creating our own versions of the code which would model the galaxies for the majority of the project. It would have been much more time-efficient had we taken existing code and modified it for our purpose, however we chose to start from scratch in order to develop our programming skills and learn Python. In the end, the code had many flaws and there were lots we would have liked to do if we had more time, but I consider it to have been an extremely valuable learning experience.

Thesis

The thesis submitted as part of my master’s degree can be read here:

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