The StarFISH algorithm determines the best-fit star-formation history (SFH) of a stellatr population, given multicolor photometry and a library of theoretical isochrones. The algorithm is designed to be flexible, robust and easy to use. It can be modified to use any dataset, and almost any set of isochrones. StarFISH is freely available for use by the astronomical community.
The program first constructs a library of synthetic color-magnitude diagrams (CMDs), where each CMD represents the expected photometric distribution of stars for a single-burst population of a given age and metallicity. The effects of distance, interstellar extinction, photometric errors and binarity are empirically modeled, to ensure compatibility with the observed photometry. While they do not form an orthogonal set, one can still think of the synthetic CMDs as a library of eigen-populations: they can be linearly combined to form a composite model CMD that represents the photometry of any star formation history.
We statistically compare such composite model CMDs to the observed photometry, to determine the best-fit composite model, and therefore the best-fit SFH. StarFISH does not require artificial constraints on the form of the SFH; we routinely use it to determine histories with up to 50 independent parameters.
Details about the algorithm and its performance are available in Harris & Zaristky 2001, ApJS, 136, 25. This paper is based on Chapter 4 of my Ph.D. thesis.
The Full version contains sample precompiled isochrone libraries and synthetic CMDs. The compact version does not.
You can view the ChangeLog for this release, or download the StarFISH manual separately (it is included in both download versions). Note that the manual has been updated for this release.