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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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