The optical depth to microlensing toward M31 due to known stars in the disk of M31 itself is τ ∼ 2 × 10 −7 e −r/d where d is the disk scale length and r is the distance along the major axis. Thus, there can be significant lensing toward the M31 disk even if M31 contains no dark compact objects. The optical depth has a strong dependence on azimuthal angle: at fixed radius τ ∝ [1 + (h/d) tan i co...

Using metallicities from the literature, combined with the Revised Bologna Catalogue of photometric data for M31 clusters and cluster candidates (the latter of which is the most comprehensive catalogue of M31 clusters currently available, including 337 confirmed globular clusters – GCs – and 688 GC candidates), we determine 443 reddening values and intrinsic colours, and 209 metallicities for i...

We present results from an ongoing Keck spectroscopic survey of red giant stars in a field located along the major axis of M31, ≈ 34 kpc in projection from the nucleus and near the luminous globular cluster G1. We use multislit LRIS spectroscopy to measure the Ca ii nearinfrared triplet in 41 stars ranging in apparent magnitude from 20 < I < 22. Of these, 23 stars are found to have radial veloc...

We observed 21 polarized background radio sources in the field of M31 at 1.365 GHz and 1.652 GHz, and determined their rotation measures (RMs). The RM data show that the regular magnetic field of the disk probably extends from about 5 kpc to 25 kpc from the center with similar structure. The RMs obtained from the polarized emission from M31 at λ6 cm and λ11 cm indicate that M31 might have a wea...

We present results from an ongoing Keck spectroscopic survey of red giant stars in a field located along the major axis of M31, ≈ 34 kpc in projection from the nucleus and near the luminous globular cluster G1. We use multislit LRIS spectroscopy to measure the Ca ii nearinfrared triplet in 41 stars ranging in apparent magnitude from 20 < I < 22. Of these, 23 stars are found to have radial veloc...

We report on the discovery of three new dwarf galaxies in the Local Group. These galaxies are found in new CFHT/MegaPrime g, i imaging of the southwestern quadrant of M31, extending our extant survey area to include the majority of the southern hemisphere of M31’s halo out to 150 kpc. All these galaxies have stellar populations which appear typical of dwarf spheroidal (dSph) systems. The first ...

We have studied the properties of a sample of 67 very blue and likely young massive clusters in M31 extracted from the Bologna Revised Catalog of globular clusters, selected according to their color [(B − V )o ≤ 0.45] and/or to the strength of their Hβ spectral index (Hβ ≥ 3.5 Å). Their existence in M31 has been noted by several authors in the past; we show here that these Blue Luminous Compact...

The spatial distribution of the Galactic satellite system plays an important role in Galactic dynamics and cosmology, where its successful reproduction is a key test of simulations of galaxy halo formation. Here, we examine its representative nature by conducting an analysis of the 3-dimensional spatial distribution of the M31 subgroup of galaxies, the next closest system to our own. We begin b...

We present the discovery of two new dwarf galaxies, Andromeda XXI and Andromeda XXII, located in the surroundings of the Andromeda and Triangulum galaxies (M31 and M33). These discoveries stem from the first year data of the Pan-Andromeda Archaeological Survey (PAndAS), a photometric survey of the M31/M33 group conducted with the Megaprime/MegaCam wide-field camera mounted on the Canada-France-...

We present a progress report on Washington photometry of several hundred new globular cluster (GC) candidates in M31 which were recently found from our new CCD survey of GCs. Washington CMT1 filters we used are very efficient to survey extragalactic GCs and to estimate the metallicity of GCs. Preliminary color-magnitude diagrams and color-color diagrams of the new GC candidates and known GCs in...