# Schechter Function of Galaxy Luminosity-Density relationship

1. Feb 2, 2006

### sderamus

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

2. Feb 3, 2006

### SpaceTiger

Staff Emeritus
The precise definition can be found here:

Schechter Luminosity Function

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