Related papers: The MW is an exceptionnally quiet galaxy: implicat…
As the nearest large spiral galaxy, M31 provides a unique opportunity to learn about the structure and evolutionary history of this galaxy type in great detail. Among the many observing programs aimed at M31 are microlensing studies, which…
We present internal velocity dispersions and precise radial velocities for 200 globular clusters (GCs) in M31 that are derived using new high-resolution spectra from MMT/Hectochelle. Of these, 163 also have King model structural parameters…
We examine the star-forming history (SFH) of the M31 disk during the past few hundred Myr. The luminosity functions (LFs) of main sequence stars at distances R_GC > 21 kpc (i.e. > 4 disk scale lengths) are matched by models that assume a…
Recent work by several groups has established the properties of the dwarf satellites to M31. We reexamine the reported kinematics of this group employing a fresh technique we have developed previously. By calculating the distribution of a…
We explore the possibility that extended disks, such as that recently discovered in M31, are the result of a single dwarf (10^9--10^10 Msun) satellite merger. We carry out N-body simulations of dwarf NFW halos with embedded spheriodal…
In hierarchical cosmological models, galaxies grow in mass through the continual accretion of smaller ones. The tidal disruption of these systems is expected to result in loosely bound stars surrounding the galaxy, at distances that reach…
We use a semi-analytic model of halo formation to study the dynamical history of giant field galaxies like the Milky Way. We find that in a concordance LCDM cosmology, most isolated disk galaxies have remained undisturbed for 8-10 Gyr, such…
The Local Group galaxy M33 exhibits a regular spiral structure and is close enough to permit high resolution analysis of its kinematics, making it an ideal candidate for rotation curve studies of its inner regions. Previous studies have…
(abridged) The Milky Way (MW) and Andromeda (M31) galaxies possess rotating planes of satellites. Their formation has not been explained satisfactorily yet. It was suggested that the MW and M31 satellites are ancient tidal dwarf galaxies,…
Cosmic rays, along with stellar radiation and magnetic fields, are known to make up a significant fraction of the energy density of galaxies such as the Milky Way. When cosmic rays interact in the interstellar medium, they produce gamma-ray…
We compare and contrast the stellar structures of isolated Local Group dwarf galaxies, as traced by their oldest stellar populations, with the satellite dwarf galaxies of the Milky Way and M31. All Local Group dwarfs with Mv < -6 and…
We present evidence to support an earlier indication that the Galaxy is embedded in an extended, highly inclined, triaxial halo outlined by the spatial distribution of companion galaxies to the Milky Way. Signatures of this spatial…
A Tully-Fisher (TF) relation from H-alpha rotation curves of 19 luminous, star-forming galaxies reveals there is little evidence for evolution in the mass-to-light ratio (M/L) of these galaxies to z~0.3. The near-infrared Tolman…
The center of the Milky Way galaxy (MW) is an extreme environment which contains a massive black hole surrounded by a very dense star cluster, two other adjacent star clusters, and a giant molecular cloud which would serve as an incubator…
We use observational properties of galaxies accumulated in the Updated Nearby Galaxy Catalog to derive a dark matter mass of luminous galaxies via motions of their companions. The data on orbital-to-stellar mass ratio are presented for 15…
We exploit the gravitational potential of massive cluster lenses to probe the emission line properties of six z=1 galaxies which appear as highly magnified luminous arcs. Using the GMOS integral field spectrograph together with detailed…
In previous work on galaxy clusters, several authors reported a discovery of an unusual population of galaxies, which have spiral morphologies, but do not show any star formation activity. These galaxies are called ``passive spirals'', and…
We report the discovery of an ultrafaint dwarf (UFD) galaxy, Pegasus W, located on the far side of the Milky Way-M31 system and outside the virial radius of M31. The distance to the galaxy is 915 (+60/-91) kpc, measured using the luminosity…
Gamma-ray haloes can exist around galaxies due to the interaction of escaping galactic cosmic rays with the surrounding gas. We have searched for such a halo around the nearby giant spiral Andromeda galaxy M31 using almost 7 years of Fermi…
Grand rotation curves (GRC) within ~400 kpc of M31 and the Milky Way were constructed by combining disk rotation velocities and radial velocities of satellite galaxies and globular clusters. The GRC for the Milky Way was revised using the…