Evidence for a central mass concentration in M32

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Abstract
Observations of the velocity and velocity dispersion profiles of the galaxy M32 (NGC 221) reveal an unresolved jump in the rotation curve and a central bump in the velocity dispersion. The velocity dispersion is constant at 60 km/s to within a few arc seconds of the center, where it rises to 85 km/s. The cause of the rise in the velocity dispersion is ambiguous, possibly being the result of velocity anisotropy, rotation broadening, or an actual increase in the stellar velocity dispersion. In contrast, the rotation curve is a good diagnostic of a central mass concentration. The amplitude and sharpness of the jump in the rotation of M32 are explained by an increase in mass-to-luminosity ratio (M/L) in the center. This increase of M/L in the center could be caused by a change in the stellar population, or, alternatively, the presence of central dark object of mass 5,000,000 solar masses.

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