Claude Carignan

Département de physique Université de Montréal C.P. 6128, Succursale Centre-Ville Montréal, QC Canada   H3C 3J7 Phone : +27 21 650 2395 Fax : +27 21 650 4547 Email: claude.carignan@umontreal.ca Office : B-422

Research field : Galactic kinematics and mass distribution

Description of the research project:
1. My main contribution to research in Astrophysics is the study of the mass distribution in late-type spiral and dwarf galaxies carried out in the last twenty-five years (impact – number of citations : Carignan & Freeman 1985 – 118 citations + 24 publications with more than 50 citations). This work has clearly demonstrated that the contribution of dark matter to the total mass of dwarf galaxies (∼90%) is much more important than in massive spirals (∼ 50%). Moreover, contrary to the situation in spirals where dark matter contributes mainly in the outer parts, dark matter in dwarfs contributes at all radii. This is clearly demonstrated for the galaxy DDO 154, now a prototype of its class (number of citations : Carignan & Freeman 1988 –164; Carignan & Beaulieu 1989 – 182). Most of this work was done using radio HI kinematical data. 2. The resolution reached by N-body simulations of the cosmic evolution of dark halos (NFW 1996 ; 1997) allows one to predict the inner part of halo density profiles. In principle, these profiles could be directly compared with the ones deduced from modeling the rotation curves. Unfortunately, the sensitivity of the rotation curves to the exact density profile of the halos is quite low, and one must use the highest sensitivity and the highest resolution possible to arrive at useful comparisons. Combining the high spatial resolution of Fabry-Perot (FP) Hα data to the high sensitivity but low spatial resolution of HI data, it is possible to show (Spano et al. 2008; Chemin et al. 2005; Côté et al. 2005; Blais-Ouellette et al. 2004) that the simulations are predicting halo density profiles much more centrally concentrated than what is observed. 3. In order to obtain high quality Hα kinematical data, a camera was specially developed (FaNTOmM: Hernandez et al. 2003; Gach et al. 2002) to be able to work in photon counting mode with essentially zero read-out noise. Using this instrument, surveys were carried out for barred spiral galaxies (Hernandez et al. 2005), galaxies of the SINGS sample (Dicaire et al. 2008; Daigle et al. 2005) and a sample of spirals in the Virgo Cluster (Chemin et al. 2005). Those observations were obtained at the Observatoire du mont Mégantic (1,6m) and the Observatoire de Haute-Provence (1,93m) for the objects requesting a large field and on the 4m-class CFHT and ESO (La Silla, Chile) for the more distant objects. A similar FP instrument, GHαFaS, was also built for the WHT 4,3m telescope (Carignan et al. 2008). 4. More recently, a CCD camera with zero read-out noise was developed based on an EMCCD chip (Daigle et al. 2009; 2008; 2006; 2004). The first controller giving satisfactory results for this type of chip (CCCP : a CCD Controller for Counting Photons), developed in collaboration with the Laboratoire d'Astrophysique de Marseille (LAM) and the Québec company Photon etc (a spin-off of our Laboratoire d'Astrophysique Expérimentale, LAE) was just breveted and the first one produced sold to NASA. This also gave rise to a spin-off company called Nüvü Cameras who will commercialize the new controller. This camera will unable to work in photon-counting mode with a DQE > 80% (compared to 20% for FaNTOmM) and zero read-out noise with many applications in other fields than Astrophysics. It was already chosen to equip two new instruments : the 3DNTT (Marcelin et al. 2008) on the NTT in La Silla, Chile and the BTFi (Taylor 2010) on the SOAR telescope, also in Chile. 5. It was always thought that dwarf spheroidal galaxies (dSph) were completely devoid of HI gas. This is surely not true any more since our recent high sensitivity HI observations of dSphs in the Local Group (Bouchard, Carignan & Staveley-Smith 2006) and in nearby groups (Beaulieu et al. 2006). Our first detection was for the dwarf galaxy PHOENIX (Carignan, Demers & Côté 1991). Our calculations showed that the gas mass measured was compatible with the mass loss rate expected from normal giant stars, even if the galaxy was only retaining ~1% of the gas. Observations of Sculptor with the Australia Telescope detected 20 000 solar masses of HI (Carignan et al. 1998). An interesting result is that the HI is mainly in two clouds just outside the optical body of the dwarf. This can explain why previous observations made with a 15' beam and centred on the galaxy could not detect any HI gas.

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