AAS 201st Meeting, January, 2003
Session 81. Extragalactic Star Clusters
Poster, Wednesday, January 8, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[81.03] Super Star Clusters in M82: Young Globular Clusters?

N. McCrady, A. M. Gilbert, J. R. Graham (UC Berkeley)

Using high-resolution (R ~ 22,000) near-infrared (1.51 \mum <\lambda < 1.75 \mum) spectra from Keck Observatory, we measure the kinematic masses of two super star clusters (SSCs) in M82. Cross-correlation of the spectra with template spectra of cool evolved stars gives stellar velocity dispersions of 16.2 ±0.8 km/s for cluster MGG-9 and 11.3 ±0.7 km/s for cluster MGG-11. The cluster spectra are dominated by the light of red supergiants, and correlate most closely with a template star of spectral type M0Iab. King model fits to the observed profiles of the clusters in archival HST/NICMOS images give half-light radii of 2.6 ±0.2 pc for MGG-9 and 1.15 ± 0.09 pc for MGG-11. Applying the Virial theorem, we determine masses of 1.6 ±0.3 \times 106 M\odot for MGG-9 and 3 ±1 \times 105 M\odot for MGG-11. The sizes, masses, velocity dispersions, profiles and ages of the clusters suggest that these SSCs may represent globular clusters forming in the present-day universe.

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