Stellar Populations in Star-forming Galaxies

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STELLAR POPULATIONS IN STAR-FORMING GALAXIES The morphological and chemical evolution of galaxies is a fascinating subject: how did the Universe transform itself from chaotic and chemically poor material into a wide variety of galaxies with rich chemical elements? During the last decade, this topic has gained even more interests with the development of imaging spectrographs, allowing a better grip on the small-scale physics of star formation in nearby galaxies. The study of stellar populations is an important avenue to answer questions in the field of galaxy evolution: stellar populations, as they sculpt the galaxy appearances, retain the signature of events that have been responsible for their formation and therefore, galaxy evolution. In the past years, my research has mainly focused on the description of young stellar populations in star-forming galaxies. Efforts have been dedicated to the development of SITELLE, an imaging Fourier transform spectrograph in the visible built in Québec, and to the leadership of SIGNALS, an international legacy survey with SITELLE at the Canada-France-Hawaii Telescope. SIGNALS, already underway (2018-2022), will reveal the 3D properties of more than 50 000 HII regions, i.e. ionized gas regions surrounding young star-forming populations, in ~40 nearby galaxies at an average spatial resolution of 20 pc. The proposed research here, while developing tools to identify the HII regions and measure their properties in a systematic way, will be concentrated on the low-metallicity regions in a subsample of SIGNALS irregular galaxies, and on the comparison of the HII region properties in various environments. Among others, detailed luminosity functions are to be drawn. Far-ultraviolet data from YPULS (a UVIT survey of the SIGNALS galaxies, for which I am co-PI) will be part of the analysis in order to get the best parameters for the young populations. This information is an important input for the photoionization codes used to describe the HII regions and to estimate the energy returned into the interstellar medium. In order to rebuild the complete star-formation history of the galaxies, older stellar populations will be studied using various synthesis codes based, for example, on absorption lines spectra with SITELLE. More specific questions to be addressed are related to chemical abundance variations in galaxies, small- and large-scale mixing processes in the interstellar medium, the stellar population initial mass function, and the origin and effect of the diffuse ionized gas on the star-formation rate. The homogeneous and statistically significant database of SIGNALS will lead to original and important publications. Seven students will be involved in this research program. They will work with SITELLE data and more than 60 SIGNALS experts (42% women, with great cultural diversity), a unique opportunity for the students formation and career.