Spiral and dwarf galaxies' kinematics and optical instrumentation

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The main goal of our different research projects is to determine the physical parameters (e.g. density laws, total extent) of the Dark Matter present in spiral and dwarf galaxies. The methodology used is the following. First, from 21cm HI observations obtained at the Very Large Array (New-Mexico), Westerbork (Holland), the Australia Telescope, and at DRAO (Penticton, BC), it is possible to derive the rotation curves of those galaxies over 2 to 5 times their optical diameters and thus to measure the mass present out to the last measured velocity point (kinematical mass). Those observations also give us the gas mass, which can sometimes be more important than the stellar mass in certain dwarf galaxies. Then, the light distribution (surface photometry) allows us to derive the stellar mass (using near infrared data, e.g. Spitzer). The difference between the kinematical mass and the luminous mass (stars & gas) is thus a measure of the Dark Matter component. Since the mass models are very sensitive to the rising part of the rotation curves, higher resolution 3D data, obtained from Fabry-Perot interferometry, must be combined to the HI data for the inner parts (to avoid the beam smearing effect of HI data). This is especially important if someone wants to determine whether the dark matter density profiles are flat (e.g. isothermal) or cuspy (e.g. NFW) in the very inner parts, as predicted by Cold Dark Matter cosmological simulations. In order to get the highest Signal-to-Noise data possible in the very critical inner parts, we built our own Image Photon Counting System (IPCS) called FaNTOmM, which we used not only on the 1,6m telescope of the Observatoire du mont Mégantic, but also on the 3,6m telescopes of the Canada-France-Hawaii (CFHT) and of the ESO (La Silla). The first generation of FaNTOmM used a GaAs intensifier tube which gives a DQE ~ 30% (meaning that 30% of the incoming photons are detected), as compared to ~4-5% for the old IPCS and we are working on the second generation camera based on a L3CCD chip which should provide a DQE > 80%.