Mid-infrared spectroscopy of starbursts : from Spitzer-IRS to JWST-MIRI

Abstract

The Spectral Energy Distributions (SEDs) of star-forming regions and starburst galaxies are unique tracers of the star formation processes in these environments, since they contain information on the escaping and processed photons emitted by newly formed massive stars. Understanding these internal processes is crucial in our physical interpretation of observations of unresolved star formation in the Universe. In the __rst part of this thesis, we study the physical conditions in resolved starburst regions using Bayesian __tting of their spatially integrated infrared SEDs, including both the thermal continuum and the atomic emission lines. We then apply the method to unresolved starburst to learn about their star formation physics. Our approach leads to robust constraints on physical parameters such as age, compactness, and amount of currently ongoing star formation in starburst, which are otherwise biased by model degeneracies, and allows us to link the resolved properties of giant H II regions to the star formation process at larger scales. In the second part of this thesis, we discuss the wavelength calibration of the next instrument to study the midinfrared spectral properties of starbursts, with improved resolution and sensitivity: the mid-infrared instrument (MIRI), which will __y onboard the James Webb Space Telescope in 2018.