We have obtained radial velocity measurements for 51 new globular clusters around the Sombrero galaxy. These measurements were obtained using spectroscopic observations from the AAOmega spectrograph on the Anglo-Australian Telescope and the Hydra spe
ctrograph at WIYN. Combined with our own past measurements and velocity measurements obtained from the literature we have constructed a large database of radial velocities that contains a total of 360 confirmed globular clusters. Previous studies analyses of the kinematics and mass profile of the Sombrero globular cluster system have been constrained to the inner ~9 (~24 kpc or ~5 effective radii), but our new measurements have increased the radial coverage of the data, allowing us to determine the kinematic properties of M104 out to ~15 (~41 kpc or ~9 effective radii). We use our set of radial velocities to study the GC system kinematics and to determine the mass profile and V-band mass-to-light profile of the galaxy. We find that the V-band mass-to-light ratio increases from 4.5 at the center to a value of 20.9 at 41 kpc (~9 effective radii or 15), which implies that the dark matter halo extends to the edge of our available data set. We compare our mass profile at 20 kpc (~4 effective radii or ~7.4) to the mass computed from x-ray data and find good agreement. We also use our data to look for rotation in the globular cluster system as a whole, as well as in the red and blue subpopulations. We find no evidence for significant rotation in any of these samples.
We present the results of a deep, wide-field search for transiting `Hot Jupiter (HJ) planets in the globular cluster omega Centauri. As a result of a 25-night observing run with the ANU 40-inch telescope at Siding Spring Observatory, a total of 109,7
26 stellar time series composed of 787 independent data points were produced with differential photometry in a 52x52 (0.75 deg^2) field centered on the cluster core, but extending well beyond. Taking into account the size of transit signals as a function of stellar radius, 45,406 stars have suitable photometric accuracy (<=0.045 mag to V=19.5) to search for transits. Of this sample, 31,000 stars are expected to be main sequence cluster members. All stars, both cluster and foreground, were subjected to a rigorous search for transit signatures; none were found. Extensive Monte Carlo simulations based on our actual data set allows us to determine the sensitivity of our survey to planets with radii ~1.5R_Jup, and thus place statistical upper limits on their occurrence frequency F. Smaller planets are undetectable in our data. At 95% confidence, the frequency of Very Hot Jupiters (VHJs) with periods P satisfying 1d<P<3d can be no more than F_VHJ < 1/1040 in omega Cen. For HJ and VHJ distributed uniformly over the orbital period range 1d<P<5d, F_VHJ+HJ < 1/600. Our limits on large, short-period planets are comparable to those recently reported for other Galactic fields, despite being derived with less telescope time.
