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A 20,000 Msolar Black Hole in the Stellar Cluster G1
Ho, Luis C.; Gebhardt, Karl; Rich, R. M.
We present the detection of a 2.0+1.4-0.8×104 Msolar black hole (BH) in the stellar cluster G1 (Mayall II), based on data taken with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. G1 is one of the most massive stellar clusters in M31. The central velocity dispersion (25 km …
Re-examining the X-ray versus spin-down luminosity correlation of rotation powered pulsars
Mereghetti, S.; Possenti, A.; Cerutti, R. +1 more
The empirical relation between the X-ray luminosity (in the 2-10 keV band) and the rate of spin-down energy loss Lsd of a sample of 39 pulsars is re-examined considering recent data from ASCA, RXTE, BeppoSAX, Chandra, and XMM-Newton and including statistical and systematic errors. The data show a significant scatter around an average co…
The Internal Structure and Formation of Early-Type Galaxies: The Gravitational Lens System MG 2016+112 at z = 1.004
Treu, Tommaso; Koopmans, Léon V. E.
We combine our recent measurements of the velocity dispersion and the surface brightness profile of the lens galaxy D in the system MG 2016+112 (z=1.004) with constraints from gravitational lensing to study its internal mass distribution. We find the following: (1) dark matter accounts for more than 50% of the total mass within the Einstein radius…
A New Spectral Classification System for the Earliest O Stars: Definition of Type O2
Walborn, Nolan R.; Parker, Joel Wm.; Drissen, Laurent +7 more
High-quality, blue-violet spectroscopic data are collected for 24 stars that have been classified as type O3 and that display the hallmark N IV and N V lines. A new member of the class is presented; it is the second known in the Cyg OB2 association, and only the second in the northern hemisphere. New digital data are also presented for several of …
Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15. II. Kinematic Analysis and Dynamical Modeling
Gerssen, Joris; van der Marel, Roeland P.; Gebhardt, Karl +3 more
We have used the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) to obtain high spatial resolution spectroscopy of the central region of the dense globular cluster M15. The observational strategy and data reduction were described in Paper I of this series. Here we analyze the extracted spectra with a cross-correlati…
The M 81 group of galaxies: New distances, kinematics and structure
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +7 more
We present Hubble Space Telescope/WFPC2 images of the galaxies NGC 2366, NGC 2976, NGC 4236, IC 2574, DDO 53, DDO 82, DDO 165, Holmberg I, Holmberg II, Holmberg IX, K52, K73, BK3N, Garland, and A0952+69 in the M 81 complex. Their true distance moduli, derived from the brightness of the tip of the red giant branch, lie in the range of 27fm 52 (NGC …
Interacting Coronal Mass Ejections and Solar Energetic Particles
Kaiser, M. L.; Howard, R. A.; Gopalswamy, N. +5 more
We studied the association between solar energetic particle (SEP) events and coronal mass ejections (CMEs) and found that CME interaction is an important aspect of SEP production. Each SEP event was associated with a primary CME that is faster and wider than average CMEs and originated from west of E45°. For most of the SEP events, the primary CME…
The Palomar/MSU Nearby Star Spectroscopic Survey. IV. The Luminosity Function in the Solar Neighborhood and M Dwarf Kinematics
Hawley, Suzanne L.; Gizis, John E.; Reid, I. Neill
We have used new astrometric and spectroscopic observations to refine the volume-complete sample of M dwarfs defined in previous papers in this series. With the addition of Hipparcos astrometry, our revised VC2 sample includes 558 main-sequence stars in 448 systems. Analysis of that data set shows no evidence of any systematic kinematic…
Measuring the redshift evolution of clustering: the Hubble Deep Field South
Colombi, S.; Matarrese, S.; Fontana, A. +6 more
We present an analysis of the evolution of galaxy clustering in the redshift interval 0<=z<=4.5 in the Hubble Deep Field South (HDF-South). The HST optical data are combined with infrared ISAAC/VLT observations, and photometric redshifts are used for all the galaxies brighter than IAB<=27.5. The clustering signal is obtained in…
Planetary Nebulae as Standard Candles. XII. Connecting the Population I and Population II Distance Scales
Ciardullo, Robin; Durrell, Patrick R.; Feldmeier, John J. +3 more
We report the results of [O III] λ5007 surveys for planetary nebulae (PNe) in six galaxies: NGC 2403, NGC 3115, NGC 3351, NGC 3627, NGC 4258, and NGC 5866. Using on-band/off-band [O III] λ5007 images, as well as images taken in Hα, we identify samples of PNe in these galaxies and derive their distances using the planetary nebula luminosity functio…