The Planetary Nebulae of Spiral Galaxies

This research project aims to unravel the late stages of the formation of galaxies, in particular the build-up of the extended stellar and dark matter halos of spiral galaxies, thought to be dominated by galaxy mergers and accretion events. As the dynamical timescales there are long (several gigayears), the accretion events are imprinted in the galaxies' phase-spaces. Measuring the properties f individual stars beyond our Local Group of galaxies remains extremely difficult, however, so planetary nebulae (PNe) are used instead. These discrete tracers act as lighthouses, their bright emission lines being detectable/measurable to distances of several tens of megaparsecs. The majority of PN studies to date have focused on elliptical and lenticular galaxies, but this project will break this barrier and target spiral galaxies. Indeed, a new generation of wide-field integral-field spectrographs enables us to discriminate PNe from interlopers (such as supernova remnants and star-formation regions), and in turn map for the first time the composition and kinematics of these galaxies' halos robustly. In particular, the project will relate the PN properties to the usual stellar population properties (age and metallicity) measured from integrated light, and thus constrain the galaxies' kinematics and luminous+dark matter contents all the way from their centres to their halos.

The student will be part of the SIGNALS project (star-formation, ionised gas and nebular abundances legacy survey), a guaranteed-time programme using the revolutionary imaging Fourier transform spectrograph SITELLE at the Canada-France Hawaii Telescope. SIGNALS exploits several tens of observing nights to study in detail over 40 nearby spiral galaxies, and its unprecedented field of view (over 100 times better than its competitors!) allows to simultaneously detect and characterise the PNe across the galaxies. Most of the data are already in hand, as are most of the analysis tools, so the student will dive right into the analysis of the PNe and the scientific interpretation of the data. The project is particularly suited to a student with an interest in galaxies (dynamics, formation and evolution) and observational astronomy.