| Description |
We construct a catalog of star clusters in the Triangulum Galaxy (M33). The catalog is the result of the Local Group Cluster Search (LGCS) citizen science project through Zooniverse, where users classify images from the Hubble Space Telescope (HST). We base our star cluster catalog on the fraction of the 60 users that viewed each image who identified each object as a star cluster. We derive the completeness of the catalog from analyzing 1700 synthetic clusters to determine detection limits, as well as comparing our results to previous catalogs in the literature. By weighting Zooniverse users based on how many objects they classified as star clusters that were in fact star clusters, we improve catalog completeness. The catalog improves upon previous ground based catalogs extending the catalog by approximately 1300 clusters, providing base data for further research into star formation in M33. Using the star cluster catalog, we measure the cluster mass function for 290 young star clusters in M33 whose ages and masses were derived through integrated light spectral energy distribution fitting. Our mass function fitting uses a probabilistic Markov chain Monte Carlo technique. Although fits to integrated light observations lead to larger uncertainties than from other methods, a majority of extragalactic star cluster samples rely on integrated light fitting. We compare integrated light mass function fitting results in M31 to the mass function results for the exact same clusters whose ages and masses were derived through color magnitude diagram fitting previously published. We find the truncation mass log(Mc / M!) is 0.4 dex higher than the previously published CMD value, suggesting that uncertainties on the mass estimates of individual clusters can bias the upper mass truncation parameter of the cluster mass function to significantly higher values. We then run experiments using M51, M83 and NGC628 incorporating individual cluster mass errors into a simulated mass function fit. We find that the high errors of the integrated light method of deriving ages and masses systematically biases the truncation mass towards higher masses. |
