Stellar Populations in Spiral Galaxies

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STELLAR POPULATIONS IN SPIRAL GALAXIES The evolution of galaxies is an exciting subject, mainly because or our increasing capabilities to build powerful instruments to look at large distances when galaxies were much younger, but also because we understand more about their content. Nevertheless, the assemblage and evolution of galaxy components is still not well understood. Stellar populations are good tracers of the change experienced by a galaxy over time. It is therefore proposed here to use them to gain insights into the different mechanisms that drive star formation and galaxy evolution. This research program will include SpIOMM and SITELLE, new state of the art astronomical instruments at the Observatoire du Mont-Mégantic and Canada-France-Hawaii Telescope, to obtain simultaneously spectra in the visible for every region on the whole surface of a nearby galaxy with a high spatial resolution. Emission and absorption lines seen in these datacubes will be analysed using evolutionary stellar population synthesis models and radiative transfer codes to characterize the age, chemical composition, and mass of the galaxy components. A technique to separate the signatures of the different populations that overlap in a spectrum is to be refined. A special attention is to be given to the diffused ionized gas that is contaminating the component spectral indicators. The origin of this gas is not well established yet, but becomes easier to study now with these new instruments. Young starburst regions will also be analyzed using the ultraviolet flux produced by their numerous OB stars with data from the Ultraviolet Imaging Telescope (to be launched in 2015). UVIT will be extremely useful to compare the starburst ultraviolet properties and morphology with the visible ground-based data from SpIOMM and SITELLE. The high spatial resolution offered by all these instruments will be unique to establish links between the different component properties, for example to measure chemical abundance gradients through the galactic disks. SITELLE and UVIT surveys are being designed which include nearby spiral galaxies with different properties (bar, interactions, mass) in order to understand the different mechanisms that are influencing star formation and galaxy evolution. This program is preparing the tools and setting the orientation for the study of galaxies at larger distances with the new generation of large telescopes to come.