The origin of the closest compact elliptical galaxy (cE) M32 is a longstanding problem of galaxy formation in the Local Group. Our N-body/SPH simulations suggest a new scenario in which the strong tidal field of M31 can transform a spiral galaxy into a compact elliptical. As a low luminosity spiral galaxy plunges into the central region of M31, most of the outer stellar and gaseous components o...

The POINT-AGAPE collaboration is carrying out a search for gravitational microlensing toward M31 to reveal galactic dark matter in the form of MACHOs (Massive Astrophysical Compact Halo Objects) in the halos of the Milky Way and M31. A high-threshold analysis of 3 years of data yields 6 bright, short–duration microlensing events, which are confronted to a simulation of the observations and the ...

We present nine newly discovered globular clusters in the outer halo of M31, found by a semi-automated procedure from an INT Wide Field Camera survey of the region. The sample includes a candidate at the largest known projected galactocentric radius yet from M31.

The recent Chandra X-ray observations of the nucleus of M31, combined with earlier VLA radio and HST UV spectral measurements, provide the strictest constraints thus far available on the nature of accretion onto the supermassive black hole (called M31* hereafter) in this region. One of the two newly-detected sources within roughly an arcsec of M31* may be its X-ray counterpart. If not, the X-ra...

SN 1885 was a probable subluminous SN Ia that occurred in the bulge of the Andromeda galaxy, M31, at a projected location 1600 from the nucleus. Here we present and analyze Hubble Space Telescope images of the SN 1885 remnant seen in absorption against the M31 bulge via the resonance lines of Ca i, Ca ii, Fe i, and Fe ii. Viewed in Ca ii H and K line absorption, the remnant appears as a nearly ...

We present a photometric survey of the stellar halo of the nearest giant spiral galaxy, Andromeda (M31), using Suprime-Cam on the Subaru Telescope. A detailed analysis of V I color-magnitude diagrams of the resolved stellar population is used to measure properties such as line-of-sight distance, surface brightness, metallicity, and age, and these are used to isolate and characterize different c...

It is widely believed that dark matter exists within galaxies and clusters of galaxies. Under the assumption that this dark matter is composed of the lightest, stable supersymmetric particle, assumed to be the neutralino, the feasibility of its indirect detection via observations of a diffuse gamma-ray signal due to neutralino annihilations within M31 is examined. To this end, first the dark ma...

By applying a digital ltering technique to 1550 deg 2 of the POSS-II in the vicinity of M31, we found two previously unidentiied very low surface brightness dwarf galaxies which we designate And V and VI. Follow-up imaging with the KPNO 4-m telescope resolved these into stars easily. The V-and I-band images of And V indicate a distance similar to that of M31, and {1.5. All evidence stro...

We discuss the results of the MEGA microlensing campaign towards M31. Our analysis is based on an analytical evaluation of the microlensing rate, taking into account the observational efficiency as given by the MEGA collaboration. In particular, we study the spatial and time duration distributions of the microlensing events for several mass distribution models of the M31 bulge. We find that onl...

Abstract We analyze about 12 years of Fermi -LAT data in the direction Andromeda galaxy (M31). robustly characterize its spectral and morphological properties against systematic uncertainties related to modeling Galactic diffuse emission. perform this work by adapting exploiting potential SkyFACT adaptive template fitting algorithm. reconstruct γ-ray image M31 a template-independent way, we sho...