Related papers: On the central structure of M15
Compact object clusters are likely to exist in the centre of some galaxies because of mass segregation. The high densities and velocities reached in them deserves a better understanding. The formation of binaries and their subsequent…
Gravitational wave observations can be used to accurately measure the Hubble constant $H_0$ and could help understand the present discrepancy between constraints from Type Ia supernovae and the cosmic microwave background. Neutron star…
A massive black hole resides in the center of most, perhaps all galaxies. The one in the center of our home galaxy, the Milky Way, provides a uniquely accessible laboratory for studying in detail the connections and interactions between a…
WFPC-2 images are used to study the central structure of M31, M32, and M33. The dimmer peak, P2, of the M31 double nucleus is centered on the bulge to 0.1", implying that it is the dynamical center of M31. P2 contains a compact source…
One of the most interesting astronomical objects is the Galactic Center. We concentrate our discussion on a theoretical analysis of observational data of bright stars in the IR-band obtained with large telescopes. We also discuss the…
The existence of supermassive black holes lurking in the centers of galaxies and of stellar binary systems containing a black hole with a few solar masses has been established beyond reasonable doubt. The idea that black holes of…
To probe the nature of stellar evolution in dense environments, we study the dense core of the globular cluster Messier 13 using pre-refurbishment Planetary Camera-I images obtained with the Hubble Space Telescope. We find 15 blue straggler…
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 5,000 to 180,000 stars together with a…
We present evidence that some of the compact, luminous, young star clusters recently discovered through images taken with the Hubble Space Telescope (HST) have masses comparable to those of old Galactic globular clusters. The "super star…
If the halo dark matter consists of faint baryonic stars, then these objects probably formed at an early epoch within large associations with similar dynamical properties to globular or open clusters. We use the luminosity function of…
We present a comprehensive space-based study of ten X-ray luminous galaxy clusters (L_X>=8e44erg/s[0.1-2.4keV]) at z=0.2. Hubble Space Telescope observations reveal numerous gravitationally-lensed arcs for which we present four new…
After two decades of direct dynamical simulation of large-scale structure in the universe, it is safe to say the subject is now mature. Still, there are parts of the problem that are less well developed than others. In general, the…
We analyze optical long-slit spectroscopy of the nucleus of M33 obtained from the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. Rather than the steep rise expected within the radius of influence of a supermassive…
We report on the structure of the nuclear star cluster in the innermost 0.16 pc of the Galaxy as measured by the number density profile of late-type giants. Using laser guide star adaptive optics in conjunction with the integral field…
We compare the central mass concentration of Cold Dark Matter halos found in cosmological N-body simulations with constraints derived from the Milky Way disk dynamics and from the Tully-Fisher relation. For currently favored values of the…
Black holes and neutron stars present extreme forms of matter that cannot be created as such in a laboratory on Earth. Instead, we have to observe and analyze the experiments that are ongoing in the Universe. The most telling observations…
We study the early dynamical evolution of young, dense star clusters using Monte Carlo simulations for systems with up to N~10^7 stars. Rapid mass segregation of massive main-sequence stars and the development of the Spitzer instability can…
The central bulge of M31 is observed to have two distinct brightness peaks with the separation of $\sim$ 2 pc. Tremaine (1995) recently proposed a new idea that the M31's nucleus is actually a single thick eccentric disk surrounding the…
The dynamical evolution of globular clusters (GCs) is tied to their binary population, as binaries segregate to the cluster centre, leading to an increased binary fraction in the core. This central overabundance of mainly hard binaries can…
The central regions of galaxies show the presence of massive black holes and/or dense stellar systems. The question about their modes of formation is still under debate. A likely explanation of the formation of the central dense stellar…