Stochastic stellar cluster IMFs: Models and impact on integrated cluster parameter determination

Abstract

Stellar clusters are regularly used to study the evolution of their host galaxy. Except for a few nearby galaxies, these studies rely on the interpretation of integrated cluster properties, especially integrated photometry observed using multiple filters (i.e. the Spectral Energy Distribution SED). To allow interpretation of such observations, we present a large set of GALEV cluster models using the realistic approach of adopting stochastically-sampled stellar IMFs. We provide models for a wide range of cluster masses (10^3 - 2 * 10^5$ Msun), metallicities (-2.3 <= [Fe/H] <= +0.18 dex), foreground extinction, and 184 regularly used filters. We analyze various sets of stochastic cluster SEDs by fitting them with non-stochastic models, which is the procedure commonly used in this field. We identify caveats and quantify the fitting uncertainties associated with this standard procedure. We show that this can yield highly unreliable fitting results, especially for low-mass clusters.

accepted for publication in ApJ, web page for downloading the data is available http://model.galev.org/stochastic_ssp/ (equivalent to http://data.galev.org/models/anders13/ as quoted in the paper)

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