We analyze the structural parameters of the largest-available sample of spatially resolved extragalactic globular clusters. The images of M31 GCs were found in a search of HST archival data, described in a companion paper. We measure the ellipticities and position angles of the clusters and conclude that the ellipticities are consistent with being caused by rotation. We find that most clusters’...

We present images and a color–magnitude diagram for And V, a new dwarf spheroidal companion to M31 that was found using a digital filtering technique applied to 1550 deg of the second Palomar Sky Survey. And V resolves into stars easily in follow-up 4-m V and I-band images, from which we deduce a distance of 810 ± 45 kpc using the tip of the red giant branch method. Within the uncertainties, th...

We have been monitoring M31 with HRC and ACIS onboard Chandra regularly in the past two years. By combining eight Chandra ACIS-I observations taken between 1999 to 2001, we have identified 204 X-ray sources within the central ∼ 17 ′ ×17 ′ region of M31, with a detection limit of ∼ 1.6 × 10 35 erg s −1. Of these 204 sources, 21 are identified with globular clusters, 2 with supernova remnants (on...

We study the possibility that an extended cosmic-ray leptonic and/or hadronic halo is at origin of large-scale gamma-ray emission detected from Andromeda Galaxy (M31). consider a broad ensemble non-homogeneous diffusion scenarios and injection sources. find electrons protons could be, very likely are, responsible for part, or all, M31, including out to more than 100 kpc center galaxy. also simu...

We present detailed analysis of three globular cluster X-ray sources in the XMM-Newton extended survey of M31. The X-ray counterpart to the M31 globular cluster Bo 45 (XBo 45) was observed with XMM-Newton on 2006 December 26. Its combined pn+MOS 0.3–10 keV lightcurve exhibited a r.m.s variability of ∼10%, and its 0.3–7.0 keV emission spectrum was well described by an absorbed power law with pho...

This paper is the third in the series of papers on M81 globular clusters. In this paper, we present spatial and metal abundance properties of 95 M81 globular clusters, which comprise nearly half of all the M81 globular cluster system. These globular clusters are divided into two M81 metallicity groups by a KMM test. Our results show that, the metal-rich clusters did not demonstrate a centrally ...

The dynamical evolution of the globular cluster systems in galaxies is predicted, based on the standard dynamical theory normalized to the example of the Milky Way. The major processes varying with the galactocentric distance are the tidal shocks and dynamical friction. Our simple model explains, on a quantitative basis, the observed diierences of the inner and outer populations of globular clu...

We investigate the influence of blending on the Cepheid distance scale. Blending is the close association of a Cepheid with one or more intrinsically luminous stars. High-resolution HST images are compared to our ground-based data, obtained as part of the DIRECT project, for a sample of 22 Cepheids in the M31 galaxy. The average (median) V -band flux contribution from luminous companions which ...

We construct a Galacto-Local Group rotation curve, combining the Galactic rotation curve with a diagram, where galacto-centric radial velocities of outer globular clusters and member galaxies of the Local Group are plotted against their galacto-centric distances. The high-velocity ends of this pseudo rotation curve within a radius R ∼ 150 kpc are well traced by a rotation curve calculated for t...

We present photometry from Hubble Space Telescope (HST )/Wide Field Planetary Camera 2 parallel imagery of a remote M31 field at a projected distance of ∼ 34 kpc from the nucleus near the SW major axis. This field is near the globular cluster G1, and near one of the candidate tidal plumes identified by Ferguson et al. (2002). The F606W (V ) and F814W (I) images were obtained in parallel with Sp...