We discuss a correlation between star formation activity (SFA) and luminosity of star-forming galaxies at intermediate redshifts of 0.2 ≤ z ≤ 0.6 in both cluster and field environments. Equivalent width (EW) of [Oii] is used for measurement of the SFA, and R-band absolute magnitude, MR, for the luminosity. In lessluminous (MR > ∼ − 20.7) galaxies, we find : (1) the mean EW([Oii]) of cluster gal...

The presence of large amount of “cold” (i.e. not much ionized, and substantially opaque in X–rays) matter around Active Galactic Nuclei is now a well established fact. For all Seyfert 2 galaxies observed in X–rays so far there is evidence for absorption in excess of the Galactic one. In a significant fraction of them, the column density of the absorbing matter exceeds 10 cm−2 (Maiolino et al. 1...

In this contribution, first results of deep VLT photometry (V,I) in the central region of the Hydra I galaxy cluster are presented. Many star clusters have been identified not only around several earlytype galaxies, but also in the intra-cluster field, as far as 250 kpc from the cluster center. Outside the bulges of the central galaxies NGC 3311 and NGC 3309, the intra-cluster globular cluster ...

Massive halos of hot plasma exist around some, but not all elliptical galaxies. There is evidence that this is related to the age of the galaxy. In this paper new X-ray observations are presented for three early-type galaxies that show evidence of youth, in order to investigate their X-ray components and properties. NGC 5363 and NGC 2865 were found to have X-ray emission dominated by purely dis...

We present optical and mid-infrared photometry of a statistically complete sample of 29 very faint dwarf galaxies (Mr > −15 mag) selected from the SDSS spectroscopic sample and observed in the mid-infrared with Spitzer IRAC. This sample contains nearby (redshift z . 0.005) galaxies three magnitudes fainter than previously studied samples. We compare our sample with other star-forming galaxies t...

Recent spectroscopic and morphological observational studies of galaxies around NGC 1399 in the Fornax Cluster (Drinkwater et al. 2000b) have discovered several ‘ultra-compact dwarf’ galaxies with intrinsic sizes of ∼ 100 pc and absolute B band magnitudes ranging from −13 to −11 mag. In order to elucidate the origin of these enigmatic objects, we perform numerical simulations on the dynamical e...

We examine the dynamics of the stars and globular clusters in the nearby giant elliptical galaxy M87 and constrain the mass distribution, using all the available data over a large range of radii, including higher-order moments of the stellar line-of-sight velocity distributions and the discrete velocities of over two hundred globular clusters. We introduce an extension of spherical orbit modeli...

We present the results of a meta-analysis of Keck spectra of extragalactic globular clusters (GCs) in a sample of eight galaxies, ranging from dwarfs to massive ellipticals. We infer ages for the metal-poor and metal-rich GCs in these galaxies through comparisons to Galactic GCs. Both subpopulations appear to be no younger than their Galactic counterparts, with ages & 10 Gyr. This is the larges...

Galaxy Zoo is the first study of nearby galaxies that contains reliable information about the spiral sense of rotation of galaxy arms for a sizeable number of galaxies. We measure the correlation function of spin chirality (the sense in which galaxies appear to be spinning) of face-on spiral galaxies in angular, real and projected spaces. Our results indicate a hint of positive correlation at s...

Many galaxies have taken on their familiar appearance relatively recently. In the distant Universe, galaxy morphology deviates significantly (and systematically) from that of nearby galaxies at redshifts (z) as low as 0.3. This corresponds to a time approximately 3.5 x 10(9) years in the past, which is only approximately 25% of the present age of the Universe. Beyond z = 0.5 (5 x 10(9) years in...