The CFHT Open Star Cluster Survey. I. Cluster Selection and Data Reduction

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Abstract
We present this paper in conjunction with a companion paper as the first results in the Canada-France-Hawaii Telescope Open Star Cluster Survey. This survey is a large BVR imaging data set of 19 open star clusters in our Galaxy. This data set was taken with the CFH12K mosaic CCD (42' × 28'), and the majority of the clusters were imaged under excellent photometric, subarcsecond seeing, conditions. The combination of multiple exposures extending to deep (V ~ 25) magnitudes with short (≤10 s) frames allows for studies ranging from faint white dwarf stars to bright turnoff, variable, and red giant stars. The primary aim of this survey is to catalog the white dwarf stars in these clusters and establish observational constraints on the initial-final mass relationship for these stars and the upper mass limit to white dwarf production. Additionally, we hope to better determine the properties of the clusters, such as age and distance, and also test evolution and dynamical theories by analyzing luminosity and mass functions. In order to more easily incorporate these data in further studies, we have produced a catalog of positions, magnitudes, colors, and stellarity confidence for all stars in each cluster of the survey. This reduction, along with the computed calibration parameters for all three nights of the observing run will encourage others to use these data in different astrophysical studies outside of our goals. Additionally, the data set is reduced using the new TERAPIX photometric reduction package, PSFex, which is found to compare well with other packages. This paper is intended both as a source for the astronomical community to obtain information on the clusters in the survey and as a detailed reference of reduction procedures for further publications of individual clusters. We discuss the methods employed to reduce the data and compute the photometric catalog. We reserve both the scientific results for each individual cluster and global results from the study of the entire survey for future publications. The first of these further publications is devoted to the old rich open star cluster, NGC 6819, and appears as a companion paper in the same issue of the Journal.

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