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Sersic index


The Sérsic profile (or Sérsic model or Sérsic's law) is a mathematical function that describes how the intensity of a galaxy varies with distance from its center. It is a generalization of de Vaucouleurs' law. José Luis Sérsic first published his law in 1963.

The Sérsic profile has the form

where is the intensity at . The parameter , called the "Sérsic index," controls the degree of curvature of the profile (see figure). The smaller the value of , the less centrally concentrated the profile is and the shallower (steeper) the logarithmic slope at small (large) radii is:


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