Do the homework and explore galaxy collisions

Abstract

In this paper we test a code to model the collision of galaxies. This code is based on the program GALAXY, which is proposed in Appendix J of a well-known textbook in astrophysics. The GALAXY program is in turn based on the approximation model proposed by the Toomre brothers in 1972. With this model, it was possible to demonstrate very efficiently that the tails and bridges observed by astronomers when two galaxies collide have their origin in the gravitational tidal forces. We have made several improvements to our code with respect to the one described in Appendix J, such as (i) the possibility of evolving more than two galaxies (up to N-galaxies); (ii) the placement of stars in each of the galaxies; (iii) the rotation of the galaxies according to Euler angles; and finally, (iv) coding in ansi c rather than the original Basic language. To test the code we ran the binary collision models proposed in the homework part of the book, namely the whirlpool and cartwheel models. Then we rotated the galaxies involved in the collision and examined the differences in the results. To generate more models we change the initial velocity of the disturbing galaxy. We found geometrically and physically more interesting star configurations. In addition, we ran the Stephan model with five interacting galaxies. To show the final results of the models, we use our own algorithm to perform a density smoothing procedure and create two-dimensional isodensity plots with Python. To give the reader the opportunity to practice and visualize the different scenarios, the source programs are shared in the link: https://drive.google.com/drive/ folders/1J08YVJICYWbAZbSGceO-uOZtNrCmC7Op?usp=sharing.