Spitzer photometry of discrete sources in M33

TL;DR

This study uses Spitzer IR data to analyze discrete sources in M33, evaluating IR emission as a star formation indicator and cataloging sources to improve understanding of galaxy star formation activity.

Contribution

It provides a detailed comparison of IR emission from different source types in M33 and assesses IR as a reliable star formation tracer.

Findings

IR emission correlates with star formation regions in M33

Catalog of 24 micron sources with inferred source types

Star formation rate estimates from IR and Halpha data

Abstract

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. 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 microns) of each type of object. Moreover, we generated a catalogue of 24 microns 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.