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Homework Help: Find an expression for the mass-to-light ratio

  1. Mar 28, 2010 #1
    1. The problem statement, all variables and given/known data

    Given the luminosity profile L(r)=L0e(-r/D) and the density profile p(r) = v02/(4piGr2) find an expression for the mass-to-light ratio as a function of distance from the center of the galaxy r. Assume the ratio is unity at r = D.

    3. The attempt at a solution

    At first I thought I was just supposed to divide the density profile by the luminosity profile to get v02/(4piGr2L0e(-r/D)), but at r = D, that would yield v20e/(4piGD2L0), not 1, so I'm not really sure what to do.
  2. jcsd
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