We discuss the build-up of the colour-magnitude relation. The colour-magnitude relation first appears at the bright end and the faint end appears later. Interestingly, the build-up of colour-magnitude relation is delayed in low density environments. We suggest that galaxies follow the environment-dependent down-sizing evolution.

New interest have appeared recently in observations of radio sources at the shortest radio wavelengths in connection with planned searches CMB radiation. A high sensitivity 2.7 cm receiver was installed at RATAN-600 in 1989. We discuss the results of deep surveys (“Cold”) of a ±10' strip of the sky centered on the declination of SS 433 covering an interval of 11h in R.A. carried out with the RATAN-600 telescope at 2.7 and 7.6 cm in 1987–2000.

The majority of normal disk galaxies are characterized by non-axisymmetric structures like spirals or bars. These structural elements have been widely discussed in the literature as a result of gravitational instabilities which are connected to growing density waves or global instabilities of disks. A first insight into the properties of galactic discs was provided by linear stability analysis. However, a disadvantage of linear stability analysis remained its restriction to small perturbations, both in amplitude and wavelength. Thus, numerical simulations, especially hydrodynamical and stellar-hydrodynamical simulations became a primary tool for the analysis of galactic evolution.

We present N-body simulations performed in the framework of MOND. This work is based on a numerical resolution of the modified Poisson equation derived from a Lagrangian theory of MOND. This equation is a nonlinear partial differential equation, so we first developed a code that solves this kind of equations using multigrid techniques. We compared the dynamical behaviour of a typical isolated galaxy in Newton CDM model and MOND model. In this approach, pure stellar disc are considered. For the same value of the Toomre parameter (QT), galactic discs in MOND develop a bar instability sooner than in the DM model. In a second phase the MOND bars weaken while the DM bars continue to grow by exchanging angular momentum with the halo. The bar pattern speed evolves quite differently in the two models, this affects the position of resonance like the corotation and the peanut. Then we studied the evolution of several galactic discs representing the Hubble sequence, in both models. These simulations lead to a statistical bar frequency which is closer to observations for the MOND than the DM model.

We have applied the Tremaine-Weinberg method to the SB(r)b galaxy NGC 2523 and the SB(r)0/a galaxy NGC 4245 using the Calcium Triplet in order to determine their bar pattern speeds. Assuming an inclination of 53° and a distance of 49.5 Mpc, the pattern speed of NGC 2523 is 26.2 ± 6.1 km s−1 kpc−1. The pattern speed of NGC 4245 is 75.3 ± 31.2 km s−1 kpc−1, assuming an inclination of 35.4° and a distance of 12.7 Mpc. The ratio of the corotation radius to the bar radius of NGC 2523 and NGC 4245 is 1.3 ± 0.3 and 1.1 ± 0.5, respectively.

As found in Secco (2000, 2001), the presence of a (non-baryonic) dark halo in large-scale celestial objects, can induce a scale length on the luminous spheroid through the occurrence of an unexpected maximum in the virial potential energy (Clausius Virial, CV). The above mentioned investigations were grounded on two cored power law density profiles, but the same result is shown to hold for more refined and realistic models.

We present HI observations of the elliptical galaxy NGC 2974, obtained with the VLA. These observations reveal that the previously detected HI disc in this galaxy (Kim et al. 1988) is in fact a ring. Combining the flat rotation curve with the central kinematics of the ionised gas, obtained with the integral-field spectrograph SAURON, allows us to determine the mass-to-light ratio M/L as a function of radius, ranging from 100 pc in the centre to 10 kpc at the edges of the HI ring. A dark halo is required to explain the observed rotation: at the outer radii ~70% of the total mass is dark†.

Optical and near-IR surface photometry of the halos of disk galaxies and blue compact galaxies have revealed a very red spectral energy distribution, which cannot easily be reconciled with any normal type of stellar population. Using spectral evolutionary models, we demonstrate that a stellar population with an extremely bottom-heavy initial mass function can explain the red halos of both types of objects. Because of its very high mass-to-light ratio, this halo population may account for some of the missing baryons in the local Universe.

The approaches proposed in the past for determining the pattern speeds and corotation radii of the density waves in spiral and barred galaxies are mostly limited in their scope and accuracy. In this work, we have developed a general approach for the determination of corotation radii, which is applicable to any galaxy whose density wave modes have reached quasi-steady state – a condition empirically found to be the case for most nearby disk galaxies. The method utilizes an azimuthal phase shift between the potential and the density distributions for the density wave modes, the existence and the radial variations of which are closely related to the dynamical mechanism leading to the secular evolution of the basic state of the same disk galaxies (Zhang 1996, ApJ, 457, 125). We have used this method to derive corotation radii of over 100 galaxies using the near-infrared images of the Ohio State University Bright Galaxy Survey (OSUBGS, Eskridge et al. 2002, ApJS, 143, 73).

On the basis of the astrophysical parameters of the Galactic open clusters published in the recent years, we have selected ~300 clusters completely with all measurements of their kinematical parameters. Almost all the clusters have a heliocentric distance less than 3.0 kpc. Inspecting the velocity field defined by the sample, we found some 30 clusters that have extremely large peculiar motions. All the clusters with large peculiar velocities are distant objects further than 2 kpc from the Sun, and some of them have large Galactic height |z|>0.35 kpc. The age ranges of the clusters are from 4 Myr to 1 Gyr with the intermediate age of 50 Myr.

We study the inclination dependent luminosity function (LF) of spiral galaxies of the Sloan Digital Sky Survey (SDSS). Up to 60000 sample galaxies are selected from the 2nd data release of SDSS by fracdeVr < 0.5. Magnitudes and other related photometric parameters are taken from NYU-VAGC(Blanton et al.2005). The apparent axis ratio (b/a)is used as an observational inclination indicator to define sub-samples. LFs of all 5 SDSS bands (u, g, r, i, z) are drawn for different sub-samples. Significant correlation is found between characteristic magnitudes (M*) of sub-samples and their inclinations, which can be fairly explained by dust extinction. A linear fit of the relation between M* and log(b/a) measures the M*(0) (for expected face-on spirals, with 0.2 ~ 0.3 mag brighter than that of LF of whole sample) and the intensity of dust extinction γ, for each band (Figure 1(a)). Additionally, since γ ∝ τ (optical depth), the wavelength dependent γ describes the extinction curve. Figure 1(b) shows a good linear fit that implies the extinction curve obeys the power law very well, with τλ = τV(λ/5500Å)−0.97±0.07. The power index n ~ 1 is shallower than that of the MW, LMC and SMC (n=1.1~1.5), but significantly steeper than the value of Charlot et al. (2000) (n=0.7), which under the assumption of a patchy distribution of dust in spiral galaxies. So our result implies that dust distributed in spirals, on average, are not as patchy as Charlot et al. assumed.

In the last years we have gained new insights on how ram pressure acts in detail on Virgo spiral galaxies. This has been possible due to the combination of new deep HI observations, deep polarized radio continuum observations, and detailed dynamical modelling (sticky particles and MHD). As a major result a first complete ram pressure stripping time sequence could be established for the Virgo cluster.

We present a short review on poor groups of galaxies focusing on the evolution of compact groups and formation of fossil groups. Fossil groups are systems with one dominant luminous elliptical galaxy surrounded by faint companions, in an extended X-ray halo. We will briefly discuss the possibility of fossil groups being the end-products of the merging of compact groups.

The ORELSE Survey (Observations of Redshift Evolution in Large Scale Environments) is a multi-wavelength program to study the large-scale structure around a sample of 20 z>0.6 clusters, with the goal of understanding transformative processes affecting galaxies in a broad range of environments. The survey includes (1) deep optical imaging to map structure around the clusters; (2) optical spectroscopy to confirm redshifts, map the galaxy distribution, obtain cluster masses via dynamical estimates, and measure spectral properties; (3) ground-based K-band imaging, to better constrain galaxy stellar masses and improve photometric redshift estimates; (4) near-IR spectroscopy to study post-starburst galaxies and AGN; (5) HST imaging to obtain galaxy morphologies; (6) Spitzer IRAC and MIPS imaging to separate starburst and AGN populations, and examine dusty galaxies; and (7) Chandra and VLA mapping to find X-ray and radio-loud AGN that are not evident from optical data. We discuss here the motivation and some early results.

The galaxy population at z ≲ 1 is effectively described as a combination of two distinct types: red, early-type galaxies lacking much star formation and blue, late-type galaxies with active star formation. For the red galaxy population, recent work by Bell et al. (2004) has shown that the number density of ~L* galaxies on the red sequence has risen by a factor of ~2 from z ~ 1 to z ~ 0. A variety of complementary observations suggests that the build-up of galaxies on the red sequence results from 2 distinct evolutionary trends: (1) the quenching of star formation in blue galaxies and their subsequent migration onto the red sequence and (2) the dissipationless or (“dry”) merging of red-sequence galaxies.

We have been conducting PISCES project (Panoramic Imaging and Spectroscopy of Cluster Evolution with Subaru; Kodama et al. 2005) with making use of the wide-field imaging capability of Subaru. Our motivations are first to map out large scale structures and define local envioronments of galaxies therein, and then to investigate the variation in galaxy properties as a function of environment and mass. We have completed multi-colout imaging of 8 distant clusters between 0.4 < z < 1.3 so far, and we have mapped out filamentary/clumpy structures in and around the clusters across 15–30 Mpc scales (see some examples in Fig. 1). These two clusters have secure spectroscopic confirmation of the physical association of the structures to the main body of the clusters. From the photometric and spectroscopic properties of galaxies over a wide range in environment, we have found that the truncation of galaxies is seen in the outskirts of clusters rather than in cluster cores. We have also seen a clear environmental dependence of the “down-sizing” in the sense that the stage of down-sizing is delayed in lower density environments.

We discuss how stellar galactic nuclei (SGN) form and evolve during galaxy formation and evolution based on chemodynamical simulations on the central regions (1-1000 pc) of galaxies. Our simulations demonstrate that dissipative formation of SGN through rapid transfer of gas into the central 10 pc of galaxies is more consistent with recent observations of SGN than dissipationless formation of SGN through merging of globular clusters (GCs). Nuclear structures in the remnants of major galaxy mergers between low-mass, nucleated spirals are found to depend strongly on the mass-ratio of massive black holes (MBHs) to SGN in spirals in the sense that the remnants have more distinct SGN in the mergers with the smaller MBH-to-SGN-mass-ratios. During the destruction of low-mass, nucleated galaxies by strong tidal fields of giant galaxies, SGN can remain intact. The stripped SGN can be observed as bright GCs around the giant galaxies. The color-magnitude relation of metal-poor GCs (referred to as “the blue tilt”) recently discovered for bright galaxies is similar to that of SGN, which suggests that the origin of the blue tilt is closely associated with the formation processes of SGN of gas-rich, low-mass dwarfs in the high redshift universe.

Many clues about the galaxy assembly process lurk in the faint outer regions of galaxies. Although quantitative study of these parts has been severely limited in the past, breakthroughs are now being made thanks to the combination of wide-area star counts, deep HST imagery and 8-m class spectroscopy. I highlight here some recent progress made on deciphering the fossil record encoded in the outskirts of our nearest large neighbours, M31 and M33.

I present a brief review of some of the mid-infrared properties of interacting galaxies as these were revealed using observations from the Infrared Space Observatory and Spitzer Space Telescope over the last decade. The variation of the infrared spectral energy distribution in interacting galaxies can be used as an extinction free tracer not only of the location of the star formation activity but also of the physical mechanism dominating their energy production.‡.

Deep surveys conducted during the past decades have shown that galaxies in the distant universe are generally of more irregular shapes, and are disky in appearance and in their star formation rate, compared to galaxies in similar environments in the nearby universe. Given that the merger rate between z= 2 and the local universe is far from adequate to account for this observed morphological transformation rate, an internal mechanism for the morphological transformation of galaxies is to be sought, whose operation can be further aided by environmental factors. The secular evolution mechanism, especially with the discovery of a collisionless dissipation mechanism for stars within the secular evolution paradigm, has provided just such a framework for understanding the morphological evolution of galaxies across the Hubble time. In this paper we will summarize the past theoretical results on the dynamical mechanisms for secular evolution, and highlight new results in the analysis of the observational data, which confirmed that density waves in physical galaxies possess the kind of characteristics which could produce theáobserved rates of morphological transformation for both cluster and field galaxies.