On the Optimization of Broadband Photometry for Galaxy Evolution Studies

We have derived the uncertainties to be expected in the derivation of galaxyphysical properties (star formation history, age, metallicity, reddening) whencomparing broad-band photometry to the predictions of evolutionary synthesismodels. We have obtained synthetic colors for a large sample (9000) ofartificial galaxies assuming different star formation histories, ages,metallicities, reddening values, and redshifts. The colors derived have beenperturbed by adopting different observing errors, and compared back to theevolutionary synthesis models grouped in different sets. The comparison hasbeen performed using a combination of Monte Carlo simulations, a MaximumLikelihood Estimator and Principal Component Analysis. After comparing theinput and derived output values we have been able to compute the uncertaintiesand covariant degeneracies between the galaxy physical properties as functionof (1) the set of observables available, (2) the observing errors, and (3) thegalaxy properties themselves. In this work we have considered different sets ofobservables, some of them including the standard Johnson/Cousins (UBVRI) andSloan Digital Sky Survey (SDSS) bands in the optical, the 2 Micron All SkySurvey (2MASS) bands in the near-infrared, and the Galaxy Evolution Explorer(GALEX) bands in the UV, at three different redshifts, z=0.0, 0.7, and 1.4.This study is intended to represent a basic tool for the design of futureprojects on galaxy evolution, allowing an estimate of the optimal band-passcombinations and signal-to-noise ratios required for a given scientificobjective.Comment: 20 pages, 9 postscript figures, 3 tables, accepted for publication in A