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...