Dark Matter Halo Note 1


"Main body" refers to the part of the galaxy that is inside the radius of the outermost observed gas and stars. It is essentially certain that the DM extends well beyond this radius, but beyond the last stars and gas, we cannot measure it directly and know very little about its properties. Nevertheless, measurements of galaxy satellites embedded in the outer halo and measurements of velocities in galaxy groups imply that the total amount of dark matter in a galaxy is even larger than the fractions quoted in this paragraph.

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Last update: February 7, 2000

John Kormendy (kormendy@astro.as.utexas.edu)