We study the occurrence of physical collisions between stars in young and compact star cluster. The calculations are performed on the GRAPE-4 with the starlab software environment which include the dynamical evolution and the nuclear evolution of all stars and binaries. The selection of the initial conditions is based on existing and well observed star clusters, such as R136 in the 30 Doradus r...

The galactic merger remnant NGC 7252 represents one of the most extreme poststarburst environments in the local universe. During the disk-disk merger (~400 Myr ago) this galaxy produced the largest young massive star cluster population known, including two clusters above 10^7 Msun, a factor of 100 more massive than typical globular clusters in the Milky Way. We propose ACS-HRC observations of 3...

We model the formation of high-mass stars, specifying the accretion rate in terms of the instantaneous and final mass of the star, the ambient pressure of the star-forming region and the form of polytropic pressure support of the pre-stellar gas core. The high pressures typical of Galactic regions of massive star formation allow a 100 M⊙ star to form in ∼ 105 yr with a final accretion rate ∼ 10...

I will show that photometry – if extending over a reasonable choice of passbands – can give fairly precise information about young star clusters and their evolutionary state. Optical colors alone are known to leave severe ambiguities due to degeneracies between age, metallicity and extinction. High quality photometry including U,B, V or I, and a NIR band, however, in combination with an extensi...

The evolution leading to the formation of a neutron star in the very young Westerlund 1 star cluster is investigated. The turnoff mass has been estimated to be ∼ 35 M⊙, indicating a cluster age ∼ 3 − 5 Myr. The brightest X-ray source in the cluster, CXO J164710.2-455216, is a slowly spinning (10 s) single neutron star and potentially a magnetar. Since this source was argued to be a member of th...

We present high-resolution optical and near-infrared HST observations of two adjacent regions in the fossil star-burst region in M82, B1 and B2. Age estimates date the cluster population in the fossil star-burst between ∼ 2 × 10 8 and ∼ 10 × 10 9 years, assuming solar metallicity. The star cluster population in B2 is more heavily affected by internal extinction than that in B1. Although our clu...

We present the results of a wide-field survey for H -emitting galaxies in the cluster AC 114 at z = 0:32. Spectra centred on H at the cluster redshift have been obtained for 586 galaxies to Itot 22 out to a radius of 2 h−1 50 Mpc. At most, only 10% of these were found to be H –emitting cluster members. These objects are predominantly blue and of late-type spiral morphology, consistent with them...

Recent observations and hydrodynamical simulations of star formation inside a giant molecular cloud have revealed that, within a star forming region, stars do not form evenly distributed throughout this region, but rather in small sub-clumps. It is generally believed that these subclumps merge and form a young star cluster. The time-scale of this merging process is crucial for the evolution and...

Star cluster formation is a major mode of star formation in the extreme conditions of interacting galaxies and violent starbursts. Young clusters are observed to form in a variety of such galaxies, a substantial number resembling the progenitors of globular clusters in mass and size, but with significantly enhanced metallicity. From studies of the metal-poor and metal-rich star cluster populati...