Schechter Function of Galaxy Luminosity-Density relationship

AI Thread Summary
The discussion centers on confusion regarding Equation 1.18 in Linda Sparke's "Galaxies in the Universe," specifically the introduction of the variable n-star, which represents the number density of L* galaxies, or Milky Way-sized galaxies. The value given for n-star is .019h^3 per Megaparsec, with h denoting the universe's expansion rate. The equation's context and implications for understanding galaxy luminosity and density relationships are highlighted. The participant expresses a desire for further clarification and acknowledges the need for more formal education on the topic. Overall, the conversation emphasizes the importance of understanding these variables in astrophysics.
sderamus
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Hello. I'm plowing through Linda Sparke's "Galaxies in the Universe: An Introduction". I'm enjoying it quite well and learning a lot. But then I get to Equation 1.18 in the book and am a little confused because it uses variables not previously introduced.

Not sure if I can do it here but the equation introduces a quantity n-star, but doesn't define how it gets in there or what it is. The text gives n-star's value as .019h^3 per Megaparsec. h is the expansion rate of the universe. Is this the number of stars per Megaparsec? And of course correcting for the expansion of the Universe.

I'm sure I'll have quite a few more questons as I go along with this book. Wish I had the time to take some real courses in this. Oh well.

All feedback appreciated.

TIA

Sterling
 
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The precise definition can be found here:

http://scienceworld.wolfram.com/astronomy/SchechtersLuminosityFunction.html"

You can think of it roughly as being the number density of L* galaxies, which are Milky Way-sized galaxies.
 
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