Speaker
Description
In the Milky Way Galaxy, the rotation curve is related to the mass distribution of visible matter and dark matter. By comparing the measured rotation curve with the calculated rotation curve due to visible matter, we can determine the mass density of dark matter in our galaxy. The components of visible matter includes the black hole at the center of our galaxy, the two bulges, and the galactic disk. Due to their spherical symmetry (and the shell theorem) calculating the gravitational force due to the black hole and the bulges is relatively simple. Surprisingly, calculating the gravitational force due to the galactic disk is much harder. We break up the disk into numerous rings, calculate the gravitational force due to each ring, and sum the forces due to all rings. The total gravitational force, due to these four mass distributions, can be used to calculate the rotation curve due to visible matter. Using the measured rotation curve, we extract the rotation curve due to the dark matter in our galaxy. The rotation curve can be used to determine the mass distribution of the dark matter in our galaxy.
