Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-27T08:38:19.512Z Has data issue: false hasContentIssue false
  • English
  • Français

Central Dynamics of Globular Clusters: the Case for a Black Hole in ω Centauri

Published online by Cambridge University Press:  01 September 2007

Eva Noyola ,
Karl Gebhardt  and
Marcel Bergmann
Eva Noyola
Affiliation:
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748, Garching, Germany, email: [email protected]
Karl Gebhardt
Affiliation:
Department of Astronomy, University of Texas, Austin, TX, 78723
Marcel Bergmann
Affiliation:
NOAO Gemini Science Center, Casilla 603, La Serena, Chile
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The globular cluster ω Centauri is one of the largest and most massive members of the Galactic system. Its classification as a globular cluster has been challenged making it a candidate for being the stripped core of an accreted dwarf galaxy; this and the fact that it has one of the largest velocity dispersions for star clusters in our galaxy makes it an interesting candidate for harboring an intermediate mass black hole. We measure the surface brightness profile from integrated light on an HST/ACS image, and find a central power-law cusp of logarithmic slope -0.08. We also analyze Gemini GMOS-IFU kinematic data for a 5”x5” field centered on the nucleus of the cluster, as well as for a field 14″ away. We detect a clear rise in the velocity dispersion from 18.6 kms−1 at 14″ to 23 kms−1 in the center. Given the very large core in ω Cen (2.58'), an increase in the dispersion in the central 10″ is difficult to attribute to stellar remnants, since it requires too many dark remnants and the implied configuration would dissolve quickly given the relaxation time in the core. However, the increase could be consistent with the existence of a central black hole. Assuming a constant M/L for the stars within the core, the dispersion profile from these data and data at larger radii implies a black hole mass of 4.0+0.75−1.0×104M⊙. We have also run flattened, orbit-based models and find a similar mass. In addition, the no black hole case for the orbit model requires an extreme amount of radial anisotropy, which is difficult to preserve given the short relaxation time of the cluster.

Keywords

globular clusters: individual (Omega Centauri)Galaxy: kinematics and dynamics
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S246: Dynamical Evolution of Dense Stellar Systems , September 2007 , pp. 341 - 345
Copyright
Copyright © International Astronomical Union 2008

References

Baumgardt, H., Heggie, D. C., Hut, P., & Makino, J. 2003a, MNRAS 341, 247CrossRefGoogle Scholar
Baumgardt, H., Makino, J., Hut, P., McMillan, S., & Portegies Zwart, S. 2003b, ApJL 589, L25CrossRefGoogle Scholar
Baumgardt, H., Makino, J., & Hut, P. 2005, ApJ, 620, 238CrossRefGoogle Scholar
Bedin, L., et al. 2004, ApJL, 605, L125CrossRefGoogle Scholar
Breeden, J., Cohn, H., & Hut, P. 1994, ApJ, 421, 195CrossRefGoogle Scholar
Freeman, K. C. 1993, in ASP Conf. Ser. 48: The Globular Cluster-Galaxy Connection, 608Google Scholar
Gebhardt, K., & Fischer, P. 1995, AJ, 109, 209CrossRefGoogle Scholar
Gebhardt, K., et al. 1996, AJ, 112, 105CrossRefGoogle Scholar
Gebhardt, K., et al. 2000, AJ, 119, 1157CrossRefGoogle Scholar
Gebhardt, K., et al. 2003, ApJ, 583, 92CrossRefGoogle Scholar
Gebhardt, K., Rich, R. M., & Ho, L. 2005, ApJ, 634, 1093CrossRefGoogle Scholar
Gerssen, J., van der Marel, R., Gebhardt, K., Guhathakurta, P., Peterson, R., Pryor, C. 2003, AJ, 125, 376CrossRefGoogle Scholar
Meylan, G., Mayor, M., Duquennoy, A., Dubath, P. 1995, A&A, 303, 761Google Scholar
Noyola, E., & Gebhardt, K. 2006, AJ, 132, 447CrossRefGoogle Scholar
Pooley, D., & Rappaport, S. 2006, ApJL, 644, L45CrossRefGoogle Scholar
Trager, S., King, I, & Djorgovski, S. 1995, AJ, 109, 218CrossRefGoogle Scholar
Ulvestad, et al. 2007, ApJL, 661, L151CrossRefGoogle Scholar
van den Bosch, et al. 2006, ApJ, 641, 852CrossRefGoogle Scholar
van de Ven, et al. 2006, A&A, 445, 513Google Scholar
Walcher, et al. 2005, ApJ, 618, 237CrossRefGoogle Scholar