Spectral Energy Distributions, Ages, and Metallicities of Star Clusters in M33

Abstract

In this paper, we present CCD spectrophotometry of the star clusters that were detected by Chandar, Bianchi, & Ford in the nearby spiral galaxy M33. The images were obtained with the Beijing Astronomical Observatory 60/90 cm Schmidt Telescope in 13 intermediate-band filters from 3800 to 10000 Å. The observations cover the whole area of M33 with a total integration of 32.75 hr from 1995 September 23 to 2000 August 28. This provides a multicolor map of M33 in pixels of 1″.7 × 1″.7. By aperture photometry, we obtain the spectral energy distributions of these star clusters. Using theoretical stellar population synthesis models, we also obtain the distributions of age and metallicity of these star clusters. These clusters formed continuously from ∼3 × 10 6 -10 10 yr and have a large span of metallicity from Z = 0.0004 to 0.05.