University of Oulu

Modeling galaxy interactions with Holmberg’s analog computer

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Author: Venhola, Aku1
Organizations: 1University of Oulu, Faculty of Science, Department of Physics, Astronomy
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 49 MB)
Pages: 65
Persistent link:
Language: English
Published: Oulu : A. Venhola, 2014
Publish Date: 2015-04-10
Thesis type: Master's thesis
Tutor: Salo, Jouko
Reviewer: Salo, Jouko
Laurikainen, Eija


Galaxy dynamics using simulation models has been an important research field during the last 50 years. In the beginning of the 20th century there were already extensive catalogs of galaxies which showed the large diversity of the galaxy shapes, although there was no theory to explain those. Nowadays, galaxy dynamics can be extensively studied by simulating the dark matter, star, and gas cloud orbits numerically, but before the era of modern computers constructing even a simple model was a considerable challenge.

In the beginning of the 1940’s Erik Holmberg (University of Lund) introduced his new integration procedure for galaxy simulations (Holmberg, 1941) which can be considered as a pioneering study in galaxy dynamics. In his work, Holmberg replaced gravitation with light intensity, based on the fact that they both obey the same 1/r² attenuation with distance. He modeled the interaction of two galaxies with light bulbs and came out with the conclusion that some features of the galaxies, for example tails and intergalactic bridges, can be explained by gravitational tidal forces. Holmberg’s work was significant for being the first simulation of galaxy dynamics, which could be upgraded only 20 years later, when the first simulations with electronic computers were started.

Despite the significance of the Holmberg’s simulations and the large number of citations they have received, there is no marks that the simulations would have been repeated. During the summer of 2013 I reconstructed the Holmberg’s experimental setting in the University of Oulu. The experiment was made two times: once using exactly the same parameters that Holmberg used, and another time with small changes in the initial parameters. In this thesis I introduce the Holmberg’s experiments and the theory behind that.

In chapter 2, I give a brief overview of disk galaxies and methods used in galaxy simulations. In chapter 3, I present the theoretical basis of Holmberg’s analog simulation. Chapter 4 covers the hardware and the practical realization of the experiment. In chapter 4, I represent the results and compare them with the Holmberg’s results.

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Copyright information: © Aku Venhola, 2014. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.