Is there a way of calculating the mass of a galaxy, or even a nebula from the luminosity?
I'm deleting this, and moving the question to Astronomy Stack Exchange - thanks david
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There's no way to calculate such a thing from first principles: the luminosity of a galaxy depends on how efficiently it managed to form stars out of the matter available to it. Star formation is far too complicated to admit of a first-principles calculation.
But there are empirical relationships between mass and luminosity, which have been used and refined for many years. When trying to understand the large-scale structure of the Universe, we want to know where the mass is, but what we can measure is where the light is. Hence the great interest in mass-luminosity relations. The link you provide in your edit is an example of this work. To find others, a good buzzword to search for is "mass-to-light ratio." For instance, this article might be a good place to start (although I haven't read it).