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Homework Help: Source counts

  1. Feb 19, 2010 #1
    1. The problem statement, all variables and given/known data
    if the intrinsic brightness of a class of radio galaxies fades as the universe ages, such that those that we see further away are brighter, having a linear increase in luminosity with distance r, what would be the slope of a graph of log N(s) versus log S for these objects.


    2. Relevant equations



    3. The attempt at a solution
    I know that usually, the slope would be -1.5, but as it says those that we see further away are brighter, i would expect that you would see more objects above the threshold S. So im thinking that the slope would not be -1.5.

    Instead of using S=L/(4pi r^2), would i say that L=r, as it says having a linear increase in luminosity with r?
     
  2. jcsd
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