We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 observations in F555W (∼V ) and F450W (∼B) of the intermediate-age populous star cluster NGC 416 in the Small Magellanic Cloud galaxy. We use published photometry of two other SMC populous star clusters, Lindsay 1 and Lindsay 113, to investigate the age sequence of these three star clusters. We estimate tha...

We place constraints on the formation redshifts for blue globular clusters (BGCs), independent of the details of hydrodynamics and population III star formation. We argue that BGCs and stellar halos have a common origin and that simulations of 1 Mpc boxes up to z ∼ 10 must resolve BGC formation. We present a proof-of-concept simulation that captures the formation of globular-like star clusters....

The globular clusters in the halos of large galaxies like our own are almost certainly fossil remnants of the early star-forming subsystems from which these galaxies were built. The ages of the halo clusters in our Galaxy indicate a prolonged period of galaxy building lasting at least several Gyr, and their masses indicate that they were formed in very massive star-forming complexes in protogal...

Available X-ray data are collected and organized concerning the iron and gas content of galaxy clusters and groups, together with the optical luminosity, mass and iron abundance of cluster galaxies. Moving from such a restricted number of cluster parameters several astrophysical inferences are drawn. These include the evidence for rich clusters having evolved without much baryon exchange with t...

We present a spectroscopic analysis of two galaxy clusters at z≈ 0.2, out to ∼ 4 Mpc. The two clusters VMF73 and VMF74 as identified by Vikhlinin et al. (1998) were observed with multiple object spectroscopy using MOSCA at the Calar Alto 3.5 m telescope. Both clusters lie in the ROSAT Position Sensitive Proportional Counter field R285 and were selected from the X-ray Dark Cluster Survey (Gilban...

We combine morphological classifications from deep Hubble Space Telescope (HST ) imaging of a sample of three clusters at z = 0.31 and a further nine clusters at z = 0.37–0.56 with existing spectroscopic observations of their elliptical (E) and S0 populations, to study the relative spectral properties of these two galaxy types. We have also used spectroscopic and imaging data in the Coma cluste...

Mass determinations are difficult to obtain and still frequently characterised by deceptively large uncertainties. We review below the various mass estimators used for star clusters of all ages and luminosities. We highlight a few recent results related to (i) very massive old star clusters, (ii) the differences and similarities between star clusters and cores of dwarf elliptical galaxies, and ...

In large spheroidal stellar systems, such as elliptical galaxies, one invariably finds a 10-10M⊙ supermassive black hole at their centre. In contrast, within dwarf elliptical galaxies one predominantly observes a 10-10M⊙ nuclear star cluster. To date, few galaxies have been found with both type of nuclei coexisting and even less have had the masses determined for both central components. Here w...

We present Hα-derived star-formation rates (SFRs) for the galaxy cluster CL J0023+0423B at z = 0.845. Our 3σ flux limits corresponds to a star-formation rate of 0.24 h −2 100 M ⊙ yr −1 , and our minimum reliable Hα + [N II] equivalent width is > 10Å, demonstrating that near-infrared narrow-band imaging can sample the star-forming galaxy population in distant clusters. Comparison with spectrosco...

Recent high-resolution observations with the Hubble Space Telescope (HST) reveal that young star clusters of extraordinary luminosity and compactness (“super star clusters”) are commonly found in starburst systems. Cluster formation appears to be a dominant mode of star formation in starbursts. The principal properties of the young clusters are summarized. A new ultraviolet HST imaging survey o...