Fig. 1
Different catalogs of clusters used in this paper: Fan & de Grijs (2014) in open red circles, Ma (2012, 2013) in open blue squares, San Roman et al. (2010) in green diamonds, San Roman et al. (2009) in violet crosses. The three dashed ellipses have semi-major axes of 10′, 20′, and 30′ to the center (marked as a large black plus symbol) and can be seen as circles of the same radii projected on the M 33 disk.
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