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Paper: The Dark Matter Halo Shape of NGC 2976 via Stellar Kinematics
Volume: 432, New Horizons in Astronomy: Frank N. Bash Symposium 2009
Page: 175
Authors: Adams, J. J.; Gebhardt, K.; Hill, G. J.; Blanc, G. A.; van den Bosch, R.
Abstract: The observations of kinematics in low surface brightness (LSB) and dwarf late type galaxies have stubbornly resisted giving clear evidence for the cuspy Navarro-Frenk-White (NFW) dark matter (DM) halo profiles that simulations with ACDM inputs predict (Navarro, Frenk, & White 1996a). Instead, most LSBs and late type dwarfs suggest cored DM halos (Kuzio de Naray, McGaugh, & de Blok 2008) or the observations are not yet constraining enough to rule out cusps (Swaters et al. 2003; Simon et al. 2005). The most viable theory to explain cored DM halos relies on the gravitational perturbation of a growing baryonic disk that is then rapidly removed causing the halo to expand to a cored equilibrium (Navarro, Eke, & Frenk 1996b), so this problem looms large over small galaxy formation and growth. Some works have studied nearby disk galaxy kinematics for DM halo shapes with longslit stellar kinematics (Corsini et al. 1999; Corbelli & Walterbos 2007), but the best constraints come from 2D spectroscopy. So far, NGC 2976 has made the cleanest case for a cored DM halo via gaseous kinematics (Simon et al. 2003). We here report on observations of NGC 2976 with the large field-of-view fiber fed Visible Integral field Replicable Unit Spectrograph Prototype (VIRUS-P) (Hill et al. 2008) to concurrently measure the gaseous and stellar kinematics and probe the DM halo. We find a velocity field likely indicating a weak bar's influence. We cannot yet discriminate between a cuspy DM halo or a purely baryonic potential, but our data and models disfavor a cored DM halo.
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