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Galaxy in a Bottle: Simulating Spiral Galaxy Formation

BY ZACHARY SLEPIAN ⋅ DECEMBER 26, 2013 ⋅ 

Title: The Aquila comparison Project: The Effects of Feedback and Numerical Methods on Simulations of Galaxy
http://arxiv.org/abs/1112.0315
Formation Authors: C Scannapieco et al.
First Author’s Institution: Leibniz-Institute for Astrophysics PotsdamPaper Status: Published in Monthly Notices of the Royal Astronomical Society

The first “computer simulation” of structure formation, in 1941, used 37 moveable lightbulbs to mimic gravity’s inverse-square force law.  Modeling galaxy formation has come a long way since then!  Today, I will discuss the Aquila comparison of many of the major codes currently used to simulate galaxy formation. Published in 2012, this paper is important because simulations are one of the only ways we can do experiments on Galaxy-scales: begin with initial conditions, add in our best understanding of physical processes like supernovae, stellar winds, active galactic nuclei, and star formation, and see what unfolds. Comparison of different simulation codes is critical because it should show what aspects of the results are from the physics and what are from the algorithms used to compute the physics.

The ultimate test of science is how it stacks up against observation.  The Aquila project compared 13 different runs with 4 different codes, with some runs using different prescriptions for feedback  but the same code. Unfortunately, none of the runs duplicated a spiral galaxy that agrees well with observations.  Most runs rather form messy, bulgy galaxies, and of those that do form spirals, the gas is too concentrated towards the center of the galaxy, leading to unrealistic rotation curves and failure to satisfy the Tully-Fisher relation, which connects rotation speed with amount of mass in stars...
continued at http://astrobites.org/2013/12/26/galaxy ... formation/