Recent work on globular cluster systems in dwarf galaxies outside the Local Group is reviewed. Recent large imaging surveys with the Hubble Space Telescope and follow-up spectroscopy with 8-m class telescopes now allow us to compare the properties of massive star clusters in a wide range of galaxy types and environments. This body of work provides important constraints for theories of galaxy an...

Pixel-by-pixel colour-magnitude and colour-colour diagrams – based on a subset of the Hubble Space Telescope Advanced Camera for Surveys Early Release Observations – provide a powerful technique to explore and deduce the star and star cluster formation histories of the Mice and the Tadpole interacting galaxies. In each interacting system we find some 40 bright young star clusters (20 . F606W(ma...

We study the motion of stars in a star cluster which revolves in a circular orbit about its parent galaxy. The star cluster is modelled as an ellipsoid of uniform spatial density. We exhibit two 2-parameter families of self-consistent equilibrium models in which the velocity at each point is confined to a line in velocity space. We exhibit the link between this problem and that of a uniform rot...

We developed a new direct-tree hybrid N -body algorithm for fully self-consistent N -body simulations of star clusters in their parent galaxies. In such simulations, star clusters need high accuracy, while galaxies need a fast scheme because of the large number of the particles required to model it. In our new algorithm, the internal motion of the star cluster is calculated accurately using the...

The Galactic center (GC) provides a unique laboratory for a detailed examination of the interplay between massive star formation and the nuclear environment of our Galaxy. Here, we present an 100 ks Chandra ACIS observation of the Arches and Quintuplet star clusters. We also report on a complementary mapping of the dense molecular gas near the Arches cluster made with the Owens Valley Millimete...

Selected References Traditional Star Coordinates displays a multi-variate data set by mapping it to two Cartesian dimensions. This technique facilitates cluster discovery and multi-variate analysis, but binding to two dimensions hides features of the data. Threedimensional Star Coordinates spreads out data elements to reveal features. This allows the user more intuitive freedom to explore and p...

We determined ages for 52 star clusters with masses ≤ 10 M⊙ in the low surface brightness spiral galaxy NGC 45. Four of these candidates are old globular clusters located in the bulge. The remaining ones span a large age range. The cluster ages suggest a continuous star/cluster formation history without evidence for bursts, consistent with the galaxy being located in a relatively unperturbed en...

The W49A star-forming region is embedded in a 10 6 M ⊙ molecular cloud, one of the most massive in our Galaxy. It has been long known as one of the most luminous radio H II regions, containing 30 − 40 compact and ultracompact H II regions and several hot cores. We have detected a previously unknown massive star cluster (Cluster 1) embedded in the W49 molecular cloud using JHKs observations with...

New optical MK classification spectra have been obtained for 14 OB star candidates identified by Comerón et al. (2002) and presumed to be possible members of the Cyg OB2 cluster as recently described by Knödlseder (2000). All 14 candidate OB stars observed are indeed early-type stars, strongly suggesting the remaining 31 candidates by Comerón et al. are also early-type stars. A thorough investi...

Mass segregation in a star cluster is studied in an analytical manner. We consider a two-component cluster, which consists of two types of stars with different masses. Plummer’s model is used for the initial condition. We trace the overall behaviors of the probability distribution functions of the two components and obtain the timescale of mass segregation as a simple function of the cluster pa...