Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2009/iii/paper-65/4/v/solution

A flux-limited galaxy selection samples a much larger volume for bright galaxies: in the nearby Euclidean limit , hence , so very numerous faint dwarf galaxies are usually detectable only nearby. With a Schechter function , detected counts per logarithmic luminosity interval scale as and, for to , peak near rather than at the numerous faint end. The competition between increasing survey volume and the bright-end cutoff concentrates detected luminosities near , with the precise width depending on the selection and survey depth.

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