The oldest and most metal-poor Milky Way stars form a kinematically hot halo, which motivates the two major formation scenarios for our galaxy: extended hierarchical accretion and rapid collapse. RR Lyrae stars are excellent tracers of old and metal-poor populations. We measured the kinematics of 43 RR Lyrae stars in the inner regions of the nearby Large Magellanic Cloud (LMC) galaxy. The veloc...

Ongoing star formation in the Milky Way requires continuous gaseous fuel from accretion. Previous work has suggested that the accretion of dwarf galaxies could provide the needed gas for this process. In this work we investigate whether dwarf galaxy accretion is consistent with the radial profile of star formation observed in the Milky Way, which is strongly concentrated toward the center of th...

Measuring the proper motions and geometric distances of galaxies within the Local Group is very important for our understanding of its history, present state and future. Currently, proper motion measurements using optical methods are limited only to the closest companions of the Milky Way. However, given that VLBI provides the best angular resolution in astronomy and phasereferencing techniques...

We present a new model of the three-dimensional distribution of molecular gas in the Milky Way Galaxy, based on CO line data. Our analysis is based on a gas-flow simulation of the inner Galaxy using smoothed-particle hydrodynamics (SPH) using a realistic barred gravitional potential derived from the observed COBE/DIRBE near-IR light distribution. The gas model prescribes the gas orbits much bet...

We investigate the properties of Giant Molecular Clouds (GMCs) in the molecule-rich galaxy M64 (NGC 4826). In M64, the mean surface density of molecular gas is 2N (H 2) ∼ 10 22 over a 2 kpc region, equal to the surface densities of individual GMCs in the Milky Way. We observed the J = 1 → 0 transitions of CO, 13 CO, and HCN. The line ratio W CO /W 13CO for 200 pc < R gal < 800 pc is comparable ...