Recent observational results on high spatial resolution images of ultraluminous infrared galaxies (ULIGs) have revealed very luminous, young, compact, and heavily obscured super star clusters in their central regions, suggested to be formed by gas-rich major mergers. By using stellar and gaseous numerical simulations of galaxy mergers, we firstly demonstrate that the central regions of ULIGs ar...

There is growing evidence that some star-forming galaxies at z > 1 are characterized by high efficiencies and specific star formation rates. In the local universe, these traits are shared by “active” Blue Compact Dwarf galaxies (BCDs) with compact and dense star-forming regions. The Spectral Energy Distributions (SEDs) of these BCDs are dominated by young massive star clusters, embedded in a co...

We present velocity dispersion measurements of 14 globular clusters in NGC 5128 (Centarus A) obtained with the MIKE echelle spectrograph on the 6.5m Magellan Clay telescope. These clusters are among the most luminous globular clusters in NGC 5128 and have velocity dispersions comparable to the most massive clusters known in the Local Group, ranging from 10 – 30 km s−1. We describe in detail our...

We present velocity dispersion measurements of 14 globular clusters in NGC 5128 (Centarus A) obtained with the MIKE echelle spectrograph on the 6.5m Magellan Clay telescope. These clusters are among the most luminous globular clusters in NGC 5128 and have velocity dispersions comparable to the most massive clusters known in the Local Group, ranging from 10 – 30 km s−1. We describe in detail our...

We have conducted a study of optical and H I properties of spiral galaxies (size, luminosity, Hα flux distribution, circular velocity, H I gas mass) to explore the role of gas stripping as a driver of morphological evolution in clusters. We find a strong correlation between the spiral and S0 fractions within clusters, and the spiral fraction scales tightly with cluster X-ray gas luminosity. We ...

We present photometric and spectroscopic measurements of the galaxy populations in clusters from the CNOC1 sample of rich, X-ray luminous clusters at 0.18 < z < 0.55. A classical measure of the galaxy blue fraction for spectroscopically confirmed cluster members shows a significant Butcher-Oemler effect for the sample, but only when radii larger than 0.5r200 are considered. We perform a princip...

We use new models of stellar population synthesis to estimate the fraction of stars formed during the last major bursts of star formation in E/S0 galaxies in low-redshift clusters (z ∼ < 0.4) from the spectral signatures of intermediate-age stars. We find that the mass fraction of stars formed in late bursts in early-type galaxies in clusters must have decreased smoothly with redshift, from abo...

This talk investigates the formation of early-type galaxies from a deliberately observational view point. I begin by reviewing the conclusions that can be reached by comparing the detailed properties of galaxies in present-day clusters, focusing on the colour-magnitude relation in particular. The overriding picture is one of homogeneity, implying a remarkable uniformity in the formation of thes...

Stellar streams in galaxy halos are the natural consequence of a history of merging and accretion. We present evidence for a blue tidal stream of young stars in the nearest giant elliptical galaxy, NGC 5128 (Centaurus A). Using optical UBVR color maps, unsharp masking, and adaptive histogram equalization, we detect a blue arc in the northwest portion of the galaxy that traces a partial ellipse ...