Fiducial stellar population sequences for the u′g′r′i′z′ system

We describe an extensive observational project that has obtained high-quality and homogeneous photometry for a number of different Galactic star clusters ( including M92, M13, M3, M71, and NGC 6791) spanning a wide range in metallicity (-2.3 less than or similar to [ Fe/ H] less than or similar to + 0.4), as observed in the u ' g ' r ' i ' z ' passbands with the MegaCam wide-field imager on the Canada - France - Hawaii Telescope. By employing these purest of stellar populations, fiducial sequences have been defined from color - magnitude diagrams that extend from the tip of the red-giant branch down to approximately four magnitudes below the turnoff: these sequences have been accurately calibrated to the standard u ' g ' r ' i ' z ' system via a set of secondary photometric standards located within these same clusters. Consequently, they can serve as a valuable set of empirical fiducials for the interpretation of stellar populations data in the u ' g ' r ' i ' z ' system.