Description
Combining the relative vicinity of the Local Group spiral galaxy M33 with the Spitzer images, we investigate the properties of infrared (IR) emission sites and assess the reliability of the IR emission as a star formation tracer. The mid- and far-IR emission of M33 was obtained from IRAC and MIPS images from the Spitzer archive. We compared the photometric results for several samples of three known types of discrete sources (HII regions, supernovae remnants and planetary nebulae) with theoretical diagnostic diagrams, and derived the spectral energy distribution (from 3.6 to 24{mu}m) of each type of object. Moreover, we generated a catalogue of 24{mu}m sources and inferred their nature from the observed and theoretical colours of the known type sources. We estimated the star formation rate in M33 both globally and locally, from the IR emission and from the Halpha emission line.
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