The Velocity Dispersion of Globular Clusters in NGC 1399

February 1994 • 1994ApJ...422L...9G

Authors • Grillmair, Carl J. • Freeman, K. C. • Bicknell, G. V. • Carter, D. • Couch, Warrick J. • Sommer-Larsen, J. • Taylor, K.

Abstract • Low-dispersion spectra of 47 globular clusters within 9' of the core of NGC 1399 have been used to determine individual cluster velocities to a precision of ~150 km s^-1^. The sample as a whole has a mean velocity of 1518 +/- 91 km s^-1^ and a velocity dispersion of 388 +/- 54 km s^-1^. If the clusters are on purely circular orbits, we can place a lower limit on a globally constant mass-to-light (M/L) ratio of 79 +/- 20 M_sun_/L_sun_B_. This is several times larger than values of M/L determined from the stellar component closer to the core and implies that M/L must increase substantially with radius. The velocity dispersion of the globular cluster system is almost a factor of 2 larger than the velocity dispersion measured for the stellar component at 90" but is very similar to the unusually low velocity dispersion of member galaxies of the Fornax Cluster. This implies that the globular cluster system (and by extension the cD envelope) is better associated with the Fornax Cluster as a whole than with NGC 1399 itself.

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Carl Grillmair

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