The Schechter luminosity function gives the space density of galaxies within a luminosity bin. The form of the function is
where, and is a characteristic galaxy luminosity where the power-law form of the function cuts off. The parameter has units of number density and provides the normalization. The galaxy luminosity function may have different parameters for different populations and environments; it is not a universal function. One measurement from field galaxies is .
Read more about this topic: Luminosity Function (astronomy)
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