Origin of the S Stars in the Galactic Center (2008)
Löckmann, Ulf, Baumgardt, Holger, Kroupa, Pavel
Over the last 15 years, around a hundred very young stars have been observed in the central parsec of our Galaxy. While the presence of young stars forming one or two stellar disks at approx. 0.1 pc...
The Main Sequence of Star Clusters (2008)
Kuepper, Andreas H. W., Kroupa, Pavel, Baumgardt, Holger
A novel way of looking at the evolution of star clusters is presented. With a dynamical temperature, given by the mean kinetic energy of the cluster stars, and a dynamical luminosity, which is...
Evidence for primordial mass segregation in globular clusters (2008)
Baumgardt, Holger, De Marchi, Guido, Kroupa, Pavel
We have studied the dissolution of initially mass segregated and unsegregated star clusters due to two-body relaxation in external tidal fields, using Aarseth's collisional N-body code NBODY4 on...
The Nature of UCDs: Internal Dynamics from an Expanded Sample and Homogeneous Database (2008)
Mieske, Steffen, Hilker, Michael, Jordan, Andres, Infante, Leopoldo, Kissler-Patig, Markus, Rejkuba, Marina, ...
We have obtained high-resolution spectra of 23 ultra-compact dwarf galaxies (UCDs) in the Fornax cluster with -10.4>M_V>-13.5 mag (10^6
The influence of initial mass segregation on the runaway merging of stars (2008)
Ardi, Eliani, Baumgardt, Holger, Mineshige, Shin
We have investigated the effect of initial mass segregation on the runaway merging of stars. The evolution of multi-mass, dense star clusters was followed by means of direct N-body simulations of up...
Marks, Michael, Kroupa, Pavel, Baumgardt, Holger
Recently de Marchi, Paresce & Pulone (2007) studied a sample of twenty globular clusters and found that all clusters with high concentrations have steep stellar mass-functions while clusters with low...
Tracing intermediate-mass black holes in the Galactic Centre (2007)
Löckmann, Ulf, Baumgardt, Holger
We have developed a new method for post-Newtonian, high-precision integration of stellar systems containing a super-massive black hole (SMBH), splitting the forces on a particle between a dominant...
Star cluster life-times: dependence on mass, radius and environment (2007)
Gieles, Mark, Lamers, Henny, Baumgardt, Holger
The dissolution time (t_dis) of clusters in a tidal field does not scale with the ``classical'' expression for the relaxation time. First, the scaling with N, and hence cluster mass, is shallower due...
N-body simulations of star clusters (2007)
Anders, Peter, Baumgardt, Holger
Two aspects of our recent N-body studies of star clusters are presented: (1) What impact does mass segregation and selective mass loss have on integrated photometry? (2) How well compare results from...
On the efficiency of field star capture by star clusters (2007)
Mieske, Steffen, Baumgardt, Holger
An exciting recent finding regarding scaling relations among globular clusters is the so-called 'blue tilt': clusters of the blue sub-population follow a trend of redder colour with increasing...
Baumgardt, Holger, Kroupa, Pavel
We have carried out a large set of N-body simulations studying the effect of residual-gas expulsion on the survival rate and final properties of star clusters. We have varied the star formation...
Evolution of Collisionally Merged Massive Stars (2007)
Suzuki, Takeru K., Nakasato, Naohito, Baumgardt, Holger, Ibukiyama, Akihiro, Makino, Junichiro, Ebisuzaki, Toshi
We investigate the evolution of collisionally merged stars with mass of ~100 MSun which might be formed in dense star clusters. We assumed that massive stars with several tens Msun collide typically...
Carraro, Giovanni, Villanova, Sandro, Bidin, Christian Moni, Baumgardt, Holger, ...
Observations indicate that present-day star formation in the Milky Way disk takes place in stellar ensembles or clusters rather than in isolation. Bound, long lived stellar groups are known as open...
The core radius of a star cluster containing a massive black hole (2006)
Heggie, Douglas C., Hut, Piet, Mineshige, Shin, Makino, Jun, Baumgardt, Holger
(Simplified) We present a theoretical framework which establishes how the core radius of a star cluster varies with the mass of an assumed central black hole. Our result is that the ratio of core to...
Ejection of Hyper-Velocity Stars from the Galactic Centre by Intermediate-Mass Black Holes (2006)
Baumgardt, Holger, Gualandris, Alessia, Zwart, Simon Portegies
We have performed N-body simulations of the formation of hyper-velocity stars (HVS) in the centre of the Milky Way due to inspiralling intermediate-mass black holes (IMBHs). We considered IMBHs of...
Dissolution of Globular Clusters (2006)
Globular clusters are among the oldest objects in galaxies, and understanding the details of their formation and evolution can bring valuable insight into the early history of galaxies. This review...
The ecology of star clusters and intermediate mass black holes in the Galactic bulge (2005)
Zwart, Simon Portegies, Baumgardt, Holger, McMillan, Stephen L. W., Makino, Junichiro, Hut, Piet, Ebisuzaki, Toshi
We simulate the inner 100pc of the Milky-Way Galaxy to study the formation and evolution of the population of star clusters and intermediate mass black holes. For this study we perform extensive...
Lamers, Henny, Gieles, Mark, Bastian, Nate, Baumgardt, Holger, Kharchenko, Nina, Zwart, Simon Portegies
We present a simple analytical description of the disruption of star clusters in a tidal field, which agrees excellently with detailed N-body simulations. The analytic expression can be used to...
Runaway collisions in young star clusters. I. Methods and tests (2005)
Freitag, Marc, Rasio, Frederic A., Baumgardt, Holger
We present the methods and preparatory work for our study of the collisional runaway scenario to form a very massive star (VMS, M > 400 Msun) at the centre of a young, compact stellar cluster. In the...
Black Holes in Massive Star Clusters (2004)
McMillan, Steve, Baumgardt, Holger, Zwart, Simon Portegies, Hut, Piet, Makino, Junichiro
Close encounters and physical collisions between stars in young dense clusters can result in new channels for stellar evolution, and may lead to the formation of very massive stars and black holes...
Which Globular Clusters contain Intermediate-mass Black Holes? (2004)
Baumgardt, Holger, Makino, Junichiro, Hut, Piet
It has been assumed that intermediate-mass black holes (IMBHs) in globular clusters can only reside in the most centrally concentrated clusters, with a so-called `core-collapsed' density profile....
Massive Black Holes in Star Clusters. I. Equal-mass clusters (2004)
Baumgardt, Holger, Makino, Junichiro, Ebisuzaki, Toshikazu
In this paper we report results of collisional N-body simulations of the dynamical evolution of equal-mass star clusters containing a massive central black hole. Each cluster is composed of between...
Massive Black Holes in Star Clusters. II. Realistic Cluster Models (2004)
Baumgardt, Holger, Makino, Junichiro, Ebisuzaki, Toshikazu
We have followed the evolution of multi-mass star clusters containing massive central black holes through collisional N-body simulations done on GRAPE6. Each cluster is composed of between 16,384 to...
Dynamics of Intermediate Mass Black Holes in Star Clusters (2004)
Baumgardt, Holger, Zwart, Simon Portegies, McMillan, Steve, Makino, Jun, Ebisuzaki, Toshikazu
We have followed the evolution of multi-mass star clusters containing massive central black holes by N-body simulations on the GRAPE6 computers of Tokyo University. We find a strong cluster expansion...
Life and Death of Young Dense Star Clusters near the Galactic Center (2004)
Zwart, Simon Portegies, McMillan, Stephen, Baumgardt, Holger
We discuss the structural change and degree of mass segregation of young dense star clusters within about 100pc of the Galactic center. In our calculations, which are performed with GRAPE-6, the...
The formation of massive black holes through collision runaway in dense young star clusters (2004)
Zwart, Simon Portegies, Baumgardt, Holger, Hut, Piet, Makino, Junichiro, McMillan, Stephen
A luminous X-ray source is associated with a cluster (MGG-11) of young stars \~200pc from the center of the starburst galaxy M82. The properties of the X-ray source are best explained by a black hole...
A Dynamical Model for the Globular Cluster G1 (2003)
Baumgardt, Holger, Makino, Junichiro, Hut, Piet, McMillan, Steve, Zwart, Simon Portegies
We present a comparison between the observational data on the kinematical structure of G1 in M31, obtained with the Hubble WFPC2 and STIS instruments, and the results of dynamical simulations carried...
Parameters of core-collapse (2003)
Baumgardt, Holger, Heggie, Douglas C., Hut, Piet, Makino, Junichiro
This paper considers the phenomenon of deep core collapse in collisional stellar systems, with stars of equal mass. The collapse takes place on some multiple, $\xi ^{-1}$, of the central relaxation...
Dynamical evolution of star clusters in tidal fields (2002)
Baumgardt, Holger, Makino, Junichiro
We report results of a large set of N-body calculations aimed to study the evolution of multi-mass star clusters in external tidal fields. Our clusters start with the same initial mass-functions, but...
Long-term evolution of isolated N-body sytems (2002)
Baumgardt, Holger, Hut, Piet, Heggie, Douglas C.
We report results of N-body simulations of isolated star clusters, performed up to the point where the clusters are nearly completely dissolved. Our main focus is on the post-collapse evolution of...
Die Entwicklung von Systemen von Kugelsternhaufen in Galaxien / (1997)
Heidelberg, Universiẗat, Diss., 1997.