Dynamical models of  NGC 4697 and NGC 3379

Flavio de Lorenzi et al. 2008, MNRAS, 385, 1729 (to the paper)

Flavio de Lorenzi et al. 2009, MNRAS, 395, 76 (to the paper)

Typical set of observables as used to construct NMAGIC dynamical models of NGC 3379. The kinematic observations consist of integral field SAURON kinematic data (Shapiro et al. 2006) extending to ∼ 1/2-1 Re, slit kinematic data (Statler & Smecker-Hane 1999) out to ∼ 1 1/2 Re and planetary nebulae (PNe) data (Douglas et al. 2007) out to ∼7 Re, which allow to probe the outer halo. The luminosity distribution of the dynamical model is constrained from surface brightness photometric data (Capaccioli et al. 1990, Gebhardt et al. 2000). Often the surface brightness (SB) data are deprojected under some symmetry assumptions to obtain a luminosity density. For deprojecting the SB profile, we use Magorrian's (1999) deprojection method to obtain an axisymmetric intrinsic luminosity distribution.

De Lorenzi et al. (2008, 2009) combine long-slit kinematic data, SAURON data in the central region and PNe velocities and velocity dispersions in the halo to create dynamical models of the intermediate-luminosity galaxies NGC 4697 and NGC 3379 using the N-body particle code, NMAGIC. They find a range of potentials and anisotropy profiles that are consistent with the photometric and kinematic data. Therefore the inavailabilty of higher-order moments of the LOSVD in the haloes of these galaxies means the models suffer at the hands of the degeneracy existing between mass and anisotropy (and to a lesser extent, shape). As presently the discrete data provided by PNe and GCs are not of a high enough signal-to-noise ratio to derive higher order moments of the LOSVD, we need a different way to distinguish between the range of potentials and anisotropy profiles that are consistent with the data.

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