We use a Monte Carlo technique together with a simple model for the distribution of dust in M31 to investigate the observability and spatial distribution of classical novae in M31. By comparing our model positions of novae to the observed positions, we conclude that most M31 novae come from the disk population, rather than from the bulge population as has been thought. Our results indicate that...

We present several different statistical methods to determine the transverse velocity vector of M31. The underlying assumptions are that the M31 satellites on average follow the motion of M31 through space, and that the galaxies in the outer parts of the Local Group on average follow the motion of the Local Group barycenter through space. We apply the methods to the line-of-sight velocities of ...

Two independent sets of Chandra and HST images of the nuclear region of M31 allow registration of X-ray and optical images to ∼ 0.1. This registration shows that none of the bright (∼ 10erg s) X-ray sources near the nucleus is coincident with the central super-massive black hole, M31*. A 50ks Chandra HRC image shows 2.5σ evidence for a faint (3×10erg s), apparently resolved source which is cons...

The distance to the centroid of the M31 globular cluster system is determined by fitting theoretical isochrones to the observed red-giant branches of fourteen globular clusters in M31. The mean true distance modulus of the M31 globular clusters is found to be µ 0 = 24.47 ± 0.07 mag. This is consistent with distance moduli for M31 that have been obtained using other distance indicators.

We use a Monte Carlo technique together with a simple model for the distribution of dust in M31 to investigate the observability and spatial distribution of classical novae in M31. By comparing our model positions of novae to the observed positions, we conclude that most M31 novae come from the disk population, rather than from the bulge population as has been thought. Our results indicate that...

We determine the velocity vector of M31 with respect to the Milky Way and use this to constrain the mass of the Local Group, based on Hubble Space Telescope proper-motion measurements of three fields presented in Paper I. We construct N -body models for M31 to correct the measurements for the contributions from stellar motions internal to M31. This yields an unbiased estimate for the M31 center...

We have completed an intensive monitoring program of two fields on either side of the center of M31, and report here on the results concerning microlensing of stars in M31. These results stem from a three-year study (the VATT/Columbia survey) of microlensing and variability of M31 stars, emphasizing microlensing events of 3 day to 2 month timescales and likely due to masses in M31. These observ...

We provide a set of microlensing optical depth maps for M31. Optical depths towards Andromeda were calculated on the basis of a four component model of the lens and source populations: disk and bulge sources lensed by bulge, M31 halo and Galactic halo lenses. We confirm the high optical depth and the strong optical depth gradient along the M31 minor axis due to a dark halo of lenses and also di...

A velocity dispersion has been measured for the luminous globular cluster M31 037-B327, claimed to be the most massive star cluster in the Local Group and to be a young “super star cluster” that has survived to an old age. M31 037-B327 has a mass comparable to that of M31 G1 but not significantly larger. Although near the upper end for the mass distribution of globular clusters, it is not an un...

We present Keck 10-meter / LRIS spectra of candidate red giants in the halo of M31, located at a projected radius of R = 19 kpc on the minor axis. These spectroscopic targets have been selected using a combination of UBRI-based and morphological screening to eliminate background galaxies. Radial velocity measurements are used to separate M31 halo giants from foreground Milky Way dwarf stars, M3...