A Dynamical N-body model for the central region of ω Centauri

Jalali, B., Baumgardt, H., Kissler-Patig, M., Gebhardt, K., Noyola, E., Lutzgendorf, N. and de Zeeuw, P. T. (2012) A Dynamical N-body model for the central region of ω Centauri. Astronomy and Astrophysics, 538 A&A: A19.1-A19.11.


Author Jalali, B.
Baumgardt, H.
Kissler-Patig, M.
Gebhardt, K.
Noyola, E.
Lutzgendorf, N.
de Zeeuw, P. T.
Title A Dynamical N-body model for the central region of ω Centauri
Formatted title A Dynamical N-body model for the central region of ω Centauri
Journal name Astronomy and Astrophysics  (ERA 2012 Listed)    (ERA 2010 Rank A)   Check publisher's open access policy
Publication date 2012-02
Sub-type Article
DOI 10.1051/0004-6361/201116923
Volume number 538
Issue number A&A
ISSN 0004-6361; 1432-0746
Start page A19.1
End page A19.11
Total pages 11
Place of publication Les Ulis, France
Publisher E D P Sciences
Collection year 2013
Language eng
Formatted abstract Context. Supermassive black holes (SMBHs) are fundamental keys to understand the formation and evolution of their host galaxies. However, the formation and growth of SMBHs are not yet well understood. One of the proposed formation scenarios is the growth of SMBHs from seed intermediate-mass black holes (IMBHs, 102 to 105 M⊙) formed in star clusters. In this context, and also with respect to the low mass end of the M• − σ relation for galaxies, globular clusters are in a mass range that make them ideal systems to look for IMBHs. Among Galactic star clusters, the massive cluster ω Centauri is a special target due to its central high velocity dispersion and also its multiple stellar populations.

Aims. We study the central structure and dynamics of the star cluster ω Centauri to examine whether an IMBH is necessary to explain the observed velocity dispersion and surface brightness profiles.

Methods. We perform direct N-body simulations on GPU and GRAPE special purpose computers to follow the dynamical evolution of ω Centauri. The simulations are compared to the most recent data-sets in order to explain the present-day conditions of the cluster and to constrain the initial conditions leading to the observed profiles.

Results. We find that starting from isotropic spherical multi-mass King models and within our canonical assumptions, a model with a central IMBH mass of 2% of the cluster stellar mass, i.e. a 5. × 104 M⊙ IMBH, provides a satisfactory fit to both the observed shallow cusp in surface brightness and the continuous rise towards the center of the radial velocity dispersion profile. In our isotropic spherical models, the predicted proper motion dispersion for the best-fit model is the same as the radial velocity dispersion one.

Conclusions. We conclude that with the presence of a central IMBH in our models, we reproduce consistently the rise in the radial velocity dispersion. Furthermore, we always end up with a shallow cusp in the projected surface brightness of our model clusters containing an IMBH. In addition, we find that the M/L ratio seems to be constant in the central region, and starts to rise slightly from the core radius outwards for all models independent of the presence of a black hole. Considering our initial parameter space, it is not possible to explain the observations without a central IMBH for ω Centauri. To further strengthen the presence of an IMBH as a unique explanation of the observed light and kinematics more detailed analysis such as investigating the contribution of primordial binaries and different anisotropy profiles should be studied.
Keyword Methods: numerical
Black hole physics
Galaxy: kinematics and dynamics
Globular clusters: individual: omega Centauri
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Article Number: A19 ; Section: Galactic structure, stellar clusters and populations

Document type: Journal Article
Sub-type: Article
Collections: School of Mathematics and Physics
Official 2013 Collection
 
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