A Dynamical N-Body Model For The Central Region Of Omega Centauri

dc.contributor.utaustinauthorGebhardt, K.en_US
dc.creatorJalali, B.en_US
dc.creatorBaumgardt, H.en_US
dc.creatorKissler-Patig, M.en_US
dc.creatorGebhardt, K.en_US
dc.creatorNoyola, E.en_US
dc.creatorLutzgendorf, N.en_US
dc.creatorde Zeeuw, P. T.en_US
dc.description.abstractContext. 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, 10(2) to 10(5)M(circle dot)) formed in star clusters. In this context, and also with respect to the low mass end of the M-center dot - sigma 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 omega 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 omega 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 omega 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. x 104 M-circle dot 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 omega 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.en_US
dc.description.sponsorshipGerman Science foundationen_US
dc.description.sponsorshipAustralian Research Council FT0991052, NSF-0908639en_US
dc.identifier.citationJalali, B., H. Baumgardt, M. Kissler-Patig, K. Gebhardt, E. Noyola, N. Lützgendorf, and P. T. de Zeeuw. >A Dynamical N-body model for the central region of ω Centauri.> Astronomy & Astrophysics, Vol. 538 (Feb., 2012): A19.en_US
dc.relation.ispartofserialAstronomy & Astrophysicsen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.subjectmethods: numericalen_US
dc.subjectblack hole physicsen_US
dc.subjectgalaxy: kinematics and dynamicsen_US
dc.subjectglobular clusters: individual: omega centaurien_US
dc.subjectmass black-holeen_US
dc.subjectsurface-brightness profilesen_US
dc.subjectglobular-cluster g1en_US
dc.subjectvelocity dispersionen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleA Dynamical N-Body Model For The Central Region Of Omega Centaurien_US
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