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Luminosity Functions
In article ,
"PoorRichard" writes: I compiled from the literature a list of all known objects, of the type, in a region of the sky that was covered by a particular survey. n ~ 100. With that few objects, you aren't going to be able to do anything fancy. As for the completeness of the sample, that is a good question. For one thing, I restricted z 0.03. How might I further test such a sample for completeness? If it's strictly one survey, you have to know details of how it was done, though there are some tests you can apply. For example, in a magnitude-limited, the average V/V_max should be 0.5. In an ideal world, the authors of the survey would have stated their completeness, but we know that isn't always done. If it's multiple surveys, you have to understand each one and correct separately for incompleteness. In effect, you weight each object by the number of similar but undetected objects it represents. In a magnitude-limited survey, this is 1/V_max. Or if the surveys cover only a limited area of sky, just divide by the fraction of the sky that was covered. As Philip mentioned, for nearby, bright objects, the surveys may well be complete, in which case the data directly give the LF. -- Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA (Please email your reply if you want to be sure I see it; include a valid Reply-To address to receive an acknowledgement. Commercial email may be sent to your ISP.) |
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