We investigated the galaxy morphology of 6 Abell clusters at z = 0:0784 - 0:145 based on deep images obtained using MegaCam on the CFHT. For hundreds of galaxies in our data, we classified their mor- phology based on criteria related to secular or merger related evolution. We found that the morphological mixture of galaxies varies considerably from cluster to cluster. This article contains a general description of our deep imaging campaign and preliminary results for galaxy morphologies in cluster environments.

The galaxy cluster is an important object for investigating the large scale structure and evolution of galaxies. Recent wide and deep near-IR surveys provide an opportunity to search for galaxy clusters in the high redshift universe. We have identified candidate clusters of 0.8< z <1.2 from the 25 deg2 SA22 field using an optical-near-IR dataset from merged UKIDSS DXS, IMS and CFHTLS catalogs. Using these candidates, we investigate the star forming activity of member galaxies. Consequently, at z ~1, the star forming activity of cluster galaxies is not distinguishable from those of field galaxies, which is different from members in local clusters. This means the environmental effect becomes more important for M* > 1010M⊙ galaxies at z <1.

Galaxies can be "pre-processed" in the low-density outskirts by ambient medium in the filaments or tidal interactions with other galaxies while falling into the cluster. In order to probe how early on and by which mechanisms galaxies can be affected before they enter high-density cluster environments, we are carry- ing out an atomic hydrogen (H i) imaging study of a sample of galaxies selected from three filamentary structures around the Virgo cluster. Our sample consists of 14 late-type galaxies, which are potentially interacting with their surroundings. The Hi observations have been done using the Westerbork Synthesis Radio Telescope, the Giant Metrewave Radio Telescope, and the Jansky Very Large Array with column density sensitivity of ≈ 3-5 X 1019 cm-2 in 3σ per channel, which is low enough to detect faint Hi features in the outer disks of galaxies. In this work, we present the Hi data of two galaxies that were observed with GMRT. We examine the Hi morphology and kinematics to find the evidence for gas-gas and/or tidal interactions, and discuss which mechanism(s) could be responsible for pre-processing in these cases.

We present 12CO (2-1) data for four spiral galaxies (NGC 4330, NGC 4402, NGC 4522, NGC 4569) in the Virgo cluster that are undergoing different ram pressure stages. The goal is to probe the detailed molecular gas properties under strong intra-cluster medium (ICM) pressure using high-resolution millime- ter data taken with the Submillimeter Array (SMA). Combining this with Institut de RadioAstronomie Millimetrique (IRAM) data, we also study spatially resolved temperature and density distributions of the molecular gas. Comparing with multi-wavelength data (optical, Hi, UV , Hα), we discuss how molecular gas properties and star formation activity change when a galaxy experiences Hi stripping. This study suggests that ICM pressure can modify the physical and chemical properties of the molecular gas sig- nificantly even if stripping does not take place. We discuss how this affects the star formation rate and galaxy evolution in the cluster environment.

By probing nuclear regions and the overall properties of AGN hosts as a function of their environments, we aim to observationally examine how AGN activities are related to their surroundings. We have selected a representative sample of AGN hosts in the Virgo cluster. The selected galaxies are located in a range of density regions showing various morphologies in 1.4 GHz continuum emission. High-resolution obser- vations with the Korean VLBI Network (KVN) allow us to access the inner region of the AGN without suffering from dust extinction and synchrotron self-absorption. Since a number of our targets are too weak to be detected at K-band (22 GHz) within their coherence time, we applied phase referencing to calibrate fast atmospheric phase uctuations.

We classified Abell clusters using the magnitude differences between two or three bright member galaxies and investigated how such classification was correlated with the properties of brightest cluster galaxies (BCGs). S-type BCGs being clearly brighter than the rest of the member galaxies were likely to be red, luminous, and evolved as early type galaxies. On the other hand, T-type BCGs being not dominant at all were less luminous than early type galaxies. A small fraction of BCGs was currently forming stars, and all of the star-forming BCGs were T-type BCGs. Active galactic nuclei were most frequent for S-type BCGs. Through these quantitative analyses of the BCG properties, we discussed the possible scenario of BCG formation and the differences between S-type and T-type of BCGs.

We identify a strong lensing galaxy in the cluster IRC 0218 that is spectroscopically confirmed to be at z = 1:62, making it the highest-redshift strong lens galaxy known. The lens is one of the two brightest cluster galaxies and lenses a background source galaxy into an arc and a counterimage. With Hubble Space Telescope (HST) grism and Keck/LRIS spectroscopy, we measure the source redshift to be zS = 2:26. Using HST imaging, we model the lens mass distribution with an elliptical power-law prole and account for the effects of the cluster halo and nearby galaxies. The Einstein radius is θE = 0.38+0.02-0.01" (3.2+0.2 -0.1 kpc) and the total enclosed mass is Mtot(< θE) = 1.8+0.2 -0.1 X 1011 M⊙. We estimate that the cluster environment contributes ~ 10% of this total mass. Assuming a Chabrier IMF, the dark matter fraction within θE is fChab DM = 0.3+0.1 -0.3, while a Salpeter IMF is marginally inconsistent with the enclosed mass (fSalp DM = -0.3+0.2 -0.5).