Using a simple model of molecular cloud evolution, we have quantitatively estimated the change of star formation rate (SFR) of a disk galaxy falling radially into the potential well of a cluster of galaxies. The SFR is affected by the ram-pressure from the intracluster medium (ICM). As the galaxy approaches the cluster center, the SFR increases to twice the initial value, at most, in a cluster ...

By constructing a large, uniform galaxy cluster catalog from the SDSS data, we have found that cluster galaxies evolve both spectrally and morphologically. By studying the morphology– cluster-centric-radius relation, we have found two characteristic environments where galaxy morphologies change dramatically. We found passive spiral galaxies in the infalling region of clusters. They are likely t...

We present here the results of a detailed study of the X-ray properties of the cluster of galaxies Abell 3128 (z = 0.06), based on the analysis of deep (100 ks) XMM-Newton data. The most obvious feature of the X-ray morphology of A3128 is the presence of two X-ray peaks separated by ∼12. By detecting the redshifted Fe K line, we find that the Northeast (NE) X-ray peak observed toward A3128 is a...

We simulate the result of orbital decay for a dwarf satellite galaxy in a disk galaxy potential. The peeling-off of the satellite by the strong tidal field within the disk of the host galaxy quickly reduces the satellite’s mass, and drasticly slows down the decaying of the orbit. The result is generally a cluster on a large halo orbit, like the M54 cluster of the Sagittarius galaxy in the Milky...

We present deep observations taken with the HST Advanced Camera for Surveys of the central massive galaxy in a forming cluster at z = 2.2. The galaxy hosting the powerful radio source MRC 1138–262 is associated with one of the most extensive merger systems known in the early universe. Our HST/ACS image shows many star-forming galaxies merging within a ∼200 kpc region that emits both diffuse lin...

Radio, optical and X-ray observations of the powerful radio galaxy PKS 1138–262 at z = 2.156 have suggested that this galaxy is a massive galaxy in the center of a forming cluster. We have imaged 1138–262 and the surrounding 38 square arcminute field with the Very Large Telescope in a broad band and a narrow band encompassing the redshifted Lyα emission. We detect 50 objects with rest equivalen...

The proto-galaxy, cB58, was discovered in the CNOC survey of cluster redshifts. Absorption features reveal that this system is at a redshift of z = 2 : 72, implying an absolute magnitude of M v 26, and a star-formation rate of 4700M yr 1 , making it the most \active" star-forming galaxy. This proto-galaxy is observed to lie close (6 00) to a central cluster galaxy at z = 0 : 373. The X-ray prop...

We simulate the result of orbital decay for a dwarf satellite galaxy in a disk galaxy potential. The peeling-off of the satellite by the strong tidal field within the disk of the host galaxy quickly reduces the satellite’s mass, and drastically slows down the decaying of the orbit. The result is generally a cluster on a large halo orbit, like the M54 cluster of the Sagittarius galaxy in the Mil...

Radio, optical and X-ray observations of the powerful radio galaxy PKS 1138–262 at z = 2.156 have suggested that this galaxy is a massive galaxy in the center of a forming cluster. We have imaged 1138–262 and the surrounding 38 square arcminute field with the Very Large Telescopea in a broad band and a narrow band encompassing the redshifted Lyα emission. We detect 50 objects with rest equivale...

There has been plenty of observational evidence of cluster galaxy evolution such as the Butcher-Oemler effect and the morphology-density relation. However, it has been difficult to identify the origin of the cluster galaxy evolution. It has been simply difficult to trace the complicated process of galaxy evolution with several giga years of timescale, using the observation which only brings us ...