We use deep images taken with the Advanced Camera for Surveys on board the Hubble Space Telescope of the disk galaxy NGC 891, to search for globular cluster candidates. This galaxy has long been considered to be a close analog in size and structure to the Milky Way and is nearly edge-on, facilitating studies of its halo population. These extraplanar ACS images, originally intended to study the ...

We provide new nucleosynthesis yields depending on metallicity and energy (i.e., (normal supernovae and hypernovae), and show the evolution of heavy element abundances from C to Zn in the solar neighborhood. We then show the chemodynamical simulation of the Milky Way Galaxy and discuss the G-dwarf problem. We finally show the cosmological simulation and discuss the galaxy formation and chemical...

We have discovered a new Galactic satellite galaxy in the constellation of Sagittar-ius. The Sagittarius dwarf galaxy subtends an angle of 10 degrees on the sky, lies at a distance of 24 kpc and is comparable in size and luminosity to the largest dwarf spheroidal, Fornax. The new galaxy has many features in common with the other eight Galactic dwarf spheroidal systems: including an extended low...

The stellar populations of the stellar halo and of the thick disk of the Milky Way reveal much about the merging history that our Galaxy, a typical large disk galaxy, has experienced. Our current understanding, described here, implies a rather quiet evolution for the disk, back to redshifts of order 2.

We present first results from a spectroscopic survey of ∼ 2000 F/G stars 0.5–5kpc from the Galactic plane, obtained with the 2dF facility on the AAT. These data show the mean rotation velocity of the thick disk about the Galactic center a few kpc from the plane is very different than expectation, being ∼ 100km/s, rather than the predicted ∼ 180km/s. We propose that our sample is dominated by st...

A wealth of recent observational studies shows the dark matter in the Milky Way to have the following fundamental properties: 1) there is no detectable dark matter associated with the Galactic disk – the dark matter is distributed in a purely halo distribution with local volume density near the Earth ≈ 0.3GeV/cc ≡ 0.01M⊙pc; 2) The stellar mass function is both universal and convergent at low ma...