We consider the observational signature of the dynamical effects on the luminosity function of globular clusters. For the three best studied systems, in Milky Way, M31, and M87, there is a statistically significant difference between the inner and outer population of globular clusters. In all cases the inner clusters are on average brighter than the outer clusters (0.26 < ∆m0 < 0.84) and have a...

We examine the cosmological evolution of X{ray selected narrow emission line galaxies (NELGs), using a sample of 35 such objects identiied in the combined ROSAT UK Deep survey and RIXOS. This sample is entirely independent of those previously used to investigate the X{ray evolution of NELGs. We detect evolution which is at a similar rate to the evolution found in the optical luminosity function...

We examine the evolution of the sizes and number densities of disk galaxies using the high resolution images obtained by the Great Observatories Origins Deep Survey (GOODS) with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). The multiwavelength images are used to classify galaxies based on their rest–frame B-band morphologies out to redshift z ∼ 1.25. In order to min...

I review recent observations on the evolution of quasars, describe new surveys for quasars at z > 5 and for quasars with z > 3.3 down to luminosities corresponding to L* galaxies, and note the possible connection between the evolution of the star formation rate in young galaxies and the evolution of quasars.

We have studied the effect of adopting different values of the total baryonic mass surface density in the local disk at the present time, Σ(R⊙, tGal), in a model for the chemical evolution of the Galaxy. We have compared our model results with the G-dwarf metallicity distribution, the amounts of gas, stars, stellar remnants, infall rate and SN rate in the solar vicinity, and with the radial abu...

This series of papers is intended to evaluate astrocladistics in reconstructing phylogenies of galaxies. The objective of this second paper is to formalize the concept of galaxy formation and to identify the processes of diversification. We show that galaxy diversity can be expected to organize itself in a hierarchy. In order to better understand the role of mergers, we have selected a sample o...

We discuss the main ingredients necessary to build models of chemical evolution of spiral galaxies and in particular the Milky Way galaxy. These ingredients include: the star formation rate, the initial mass function, the stellar yields and the gas flows. Then we discuss models for the chemical evolution of galaxy disks and compare their predictions with the main observational constraints avail...

Hubble Space Telescope WFPC2 images of the Local Group dwarf galaxy Tucana reveal an unbiased sample of distant field galaxies. While a large number of these galaxies can be classified according to standard Hubble types, a significant number of these galaxies can be identified as "ring" galaxies, a morphology likely induced through galaxy collisions. We hav e identified seven ring galaxy candid...

The problem of galaxy formation and its dependence on thermodynamic properties is addressed by using Eulerian hydrodynamic numerical simulations of large scale structure formation. Global galaxy properties are explored in simulations including gravitation, shock heating and cooling processes, and following self-consistently the chemical evolution of a primordial composition hydrogen-helium plas...

We consider a sample of about 50 distant galaxy clusters at z > 0.15 (< z >∼ 0.3), each cluster having at least 10 galaxies with available redshift in the literature. We select member galaxies, analyze the velocity dispersion profiles, and evaluate in a homogeneous way cluster velocity dispersions and virial masses. We apply the same procedures already recently applied on a sample of nearby clu...