CHORIZOS: a CHi-square cOde for parameteRized modelIng and characteriZation of phOtometry and Spectrophotometry

Abstract

We have developed a CHi-square cOde for parameteRized modelIng and characteriZation of phOtometry and Spectrophotometry (CHORIZOS). CHORIZOS can use up to two intrinsic free parameters (e.g. temperature and gravity for stars; type and redshift for galaxies; or age and metallicity for stellar clusters) and two extrinsic ones (amount and type of extinction). The code uses chi-square minimization to find all models compatible with the observed data in the model N-dimensional (N=1,2,3,4) parameter space. CHORIZOS can use either correlated or uncorrelated colors as input and is especially designed to identify possible parameter degeneracies and multiple solutions. The code is written in IDL and is available to the astronomical community. Here we present the techniques used, test the code, apply it to a few well-known astronomical problems, and suggest possible applications. As a first scientific result from CHORIZOS, we confirm from photometry the need for a revised temperature-spectral type scale for OB stars previously derived from spectroscopy.

32 pages, 13 figures. To appear in the September 2004 issue of PASP

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