We present a study of the properties of the star-cluster systems around pseudo-bulges of late-type spiral galaxies using a sample of 11 galaxies with distances from 17 to 37 Mpc. Star clusters are identified from multiband HST ACS and WFPC2 imaging data by combining detections in 3 bands (F435W and F814W with ACS and F606W with WFPC2). The photometric data are then compared to population synthe...

The GRAPE-4, the world's fastest computer in 1995-1997, has produced some major scientific results through a wide diversity of large-scale simulations in astrophysics. Applications have included planetary formation, the evolution of star clusters and galactic nuclei, and the formation of galaxies and clusters of galaxies.

The GRAPE-4, the world's fastest computer in 1995-1997, has produced some major scientific results, through a wide diversity of large-scale simulations in astrophysics. Applications have ranged from planetary formation, through the evolution of star clusters and galactic nuclei, to the formation of galaxies and clusters of galaxies.

We investigated the color and morphology of optically selected galaxies in the region of clusters at z ∼ 1.2 near to the radio galaxy 3C 324 using archived data taken with the Hubble Space Telescope. The faint galaxies selected at the HST F702W band that contribute to the surface-density excess of the region have wide ranges of color, size, and morphology, which are not likely to be due to cont...

Most observations of the projected half-light radii of metal-rich globular clusters in a variety of galaxies have shown them to be ∼ 20% smaller than those of their metal-poor counterparts. We show using multi-mass isotropic Michie-King models that the combined effects of mass segregation and the dependence of main sequence lifetimes on metallicity can account for this difference, under the ass...

Star formation is slow, in the sense that the gas consumption time is much longer than the dynamical time. It is also inefficient; essentially all star formation in local galaxies takes place in giant molecular clouds (GMCs), but the fraction of a GMC converted to stars is very small, ∼ 5%. While there is some disagreement over the lifespan of GMCs, there is a consensus that it is no more than ...

We present new data on the globular cluster system of the elliptical galaxy NGC 3923 which show that it has the most globular clusters per unit luminosity of any noncluster elliptical yet observed, with SN = 6:4 1:4. NGC 3923 is also among the brightest ellipticals outside of a galaxy cluster for which the number of globular clusters has been determined. Our observation of a large number of clu...

A simple model is constructed to evaluate the change of star formation rate of a disk galaxy due to environmental e†ects in clusters of galaxies. Three e†ects are investigated : (1) tidal force from the potential well of the cluster, (2) increase of external pressure when the galaxy plows into the intracluster medium, and (3) high-speed encounters between galaxies. General analysis indicates th...

We study gravitational instabilities in disks, with special attention to the most massive clumps that form because they are expected to be the progenitors of globular-type clusters. The maximum unstable mass is set by rotation and depends only on the surface density and orbital frequency of the disk. We propose that the formation of massive clusters is related to this largest scale in galaxies ...