Massive star formation and evolution in starburst galaxies: Mid-infrared spectroscopy with the ISO short wavelength spectrometer

Michele D. Thornley*, Natascha M. Förster Schreiber, Dieter Lutz, Reinhard Genzel, Henrik W.W. Spoon, Dietmar Kunze, Amiel Sternberg

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

142 Scopus citations


We present new Infrared Space Observatory Short Wavelength Spectrometer data for a sample of 27 starburst galaxies, and with these data we examine the issues of formation and evolution of the most massive stars in starburst galaxies. Using starburst models which incorporate time evolution, new stellar atmosphere models for massive stars, and a starburst model geometry derived from observations of the prototypical starburst M82, we model the integrated mid-infrared line ratio [Ne III](15.6 μm)/[Ne II](12.8 μm). This line ratio is sensitive to the hardness of the stellar energy distribution and therefore to the most massive stars present. We conclude from our models, with consideration of recent determinations of the stellar census in local, high-mass star-forming regions, that the [Ne III]/[Ne II] ratios we measure are consistent with the formation of massive (∼ 50-100 M) stars in most starbursts. In this framework, the low nebular excitation inferred from the measured line ratios can be attributed to aging effects. By including estimates of the ratio of infrared-to-Lyman continuum luminosity for the galaxies in our sample, we further find that most starbursts are relatively short-lived (106-107 yr), only a few O star lifetimes. We discuss a possible cause of such short events: the effectiveness of stellar winds and supernovae in destroying the starburst environment.

Original languageEnglish
Pages (from-to)641-657
Number of pages17
JournalAstrophysical Journal
Issue number2 PART 1
StatePublished - 20 Aug 2000


  • Galaxies: starburst
  • Infrared: galaxies
  • Stars: atmospheres
  • Stars: evolution
  • Stars: formation
  • Techniques: spectroscopic


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