The occurrence of Seyfert galaxies in 6 samples representative of different cosmological environments (i.e. isolated pairs, compact and loose groups) is analysed. To avoid biases linked to subjective sample selection criteria only canonical samples, taken from the literature, are considered. It is found that the average frequency of Seyferts in all samples, is near 2%. Most Seyferts lying in pa...

We have carried out a series of small scale collisional N-body calculations of single-mass star clusters to investigate the dependence of the lifetime of star clusters on their initial parameters. Our models move through an external galaxy potential with a logarithmic density profile and they are limited by a cut-off radius. In order to find scaling relations between the lifetime of star cluste...

We combine imaging data from the Advanced Camera for Surveys (ACS) with VLT/FORS optical spectroscopy to study the properties of star-forming galaxies in the z = 0.837 cluster CL0152-1357. We have morphological information for 24 star-forming cluster galaxies, which range in morphology from late-type and irregular to compact early-type galaxies. We find that while most star-forming galaxies hav...

We present the surface photometry of star clusters in the nearby dwarf elliptical galaxies NGC 185 and NGC 205, obtained from deep HSTWFPC2 F555W (V ) and F814W (I) images. We have obtained surface brightness and color profiles of six star clusters in NGC 185, seven star clusters in NGC 205, and one recently discovered non-stellar object in NGC 205. The surface brightness profiles of ten star c...

We study how the proportion of star-forming galaxies evolves between z = 0.8 and z = 0 as a function of galaxy environment, using the [OII] line in emission as a signature of ongoing star formation. Our high-z dataset comprises 16 clusters, 10 groups and another 250 galaxies in poorer groups and the field at z = 0.4 − 0.8 from the ESO Distant Cluster Survey, plus another 9 massive clusters at s...

Aims. We investigate the build-up of stellar mass through star formation in field galaxies, galaxy groups, and clusters in order to better understand the physical processes regulating star formation in different haloes. Methods. In order to do so we relate ongoing star formation activity to the stellar mass by studying the integrated specific star formation rate (SSFR), defined as the star-form...

Our study begins by revisiting the photometric Butcher-Oemler effect using data from 7 CNOC clusters at 0.23< ∼ z<0.43. We construct the foreground/background corrected colour-magnitude diagrams for these clusters. Our analysis shows that the CNOC clusters reproduce the trend of increasing blue galaxy fraction with redshift as seen by Butcher & Oemler. We use these data to investigate the histo...

Populations of young star clusters show significant differences even among “normal” disk galaxies. In this contribution I discuss how properties of young cluster systems are related to those of their host galaxies, based on a recent study of clusters in a sample of 22 nearby spiral galaxies. Luminous young clusters similar to the “super” star clusters observed in starbursts and mergers exist in...

We investigate the star-formation properties of dynamically relaxed galaxy clusters as a function of cluster mass for 308 low-redshift clusters drawn from the Sloan Digital Sky Survey (SDSS) C4 cluster catalog. It is important to establish if cluster star-formation properties have a mass dependence before comparing clusters at different epochs, and here we use cluster velocity dispersion, σ, as...

A new HI catalog of Low Surface Brightness galaxies out to z=0.1 Abstract. Using both the Arecibo 305m and the Nançay decimetric 100-m class radio telescopes, we have observed the H i line of 116 Low Surface Brightness (LSB) galaxies from the Bothun et al. 1985 subset of LSB galaxies in the Uppsala General Catalog. The observations had a detection rate of 70%, resulting in the new determination...