If you want to calculate the mass of a galaxy using photometry, you'll need to use a stellar mass code that performs SED fitting. Two popular codes are FAST and iSEDfit. Both of these are IDL codes, so you'll need that installed and activated on your machine to use them.

FAST

FAST is the easier code to get set up. Read its page, which contains a lot of helpful info. There is a download link at the bottom of the page. Unzip the package, and put the resulting FAST_vX.X directory into your IDL directory.

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