A statistical method to determine open cluster metallicities

摘要

The study of open cluster metallicities helps to understand the local stellarformation and evolution throughout the Milky Way. Its metallicity gradient isan important tracer for the Galactic formation in a global sense. Because openclusters can be treated in a statistical way, the error of the cluster mean isminimized. Our final goal is a semi-automatic statistical robust method toestimate the metallicity of a statistically significant number of open clustersbased on Johnson BV data of their members, an algorithm that can easily beextended to other photometric systems for a systematic investigation. Thismethod incorporates evolutionary grids for different metallicities and acalibration of the effective temperature and luminosity. With clusterparameters (age, reddening and distance) it is possible to estimate themetallicity from a statistical point of view. The iterative process includes anintrinsic consistency check of the starting input parameters and allows us tomodify them. We extensively tested the method with published data for theHyades and selected sixteen open clusters within 1000pc around the Sun withavailable and reliable Johnson BV measurements. In addition, Berkeley 29, witha distance of about 15kpc was chosen. For several targets we are able tocompare our result with published ones which yielded a very good coincidence(including Berkeley 29).