Search Publications
The ACS Fornax Cluster Survey. II. The Central Brightness Profiles of Early-Type Galaxies: A Characteristic Radius on Nuclear Scales and the Transition from Central Luminosity Deficit to Excess
Jordán, Andrés; Infante, Leopoldo; Tonry, John L. +9 more
We analyze brightness profiles for 143 early-type galaxies in the Virgo and Fornax Clusters, observed with the Advanced Camera for Surveys on the Hubble Space Telescope. Sérsic models are found to provide accurate representations of the global profiles with a notable exception: the observed profiles deviate systematically inside a characteristic `…
Simultaneous Multiwavelength Observations of the Low/Hard State of the X-Ray Transient Source SWIFT J1753.5-0127
D'Avanzo, P.; Frontera, F.; Goldoni, P. +11 more
We report the results of simultaneous multiwavelength observations of the X-ray transient source SWIFT J1753.5-0127 performed with INTEGRAL, RXTE, NTT, REM, and VLA on 2005 August 10-12. The source, which underwent an X-ray outburst since 2005 May 30, was observed during the INTEGRAL Target of Opportunity program dedicated to new X-ray novae locat…
Interaction between a Fast Rotating Sunspot and Ephemeral Regions as the Origin of the Major Solar Event on 2006 December 13
Zhang, Jun; Li, Leping; Song, Qiao
The major solar event on 2006 December 13 is characterized by the approximately simultaneous occurrence of a heap of hot ejecta, a great two-ribbon flare, and an extended Earth-directed coronal mass ejection. We examine the magnetic field and sunspot evolution in NOAA AR 10930, the source region of the event, while it transited the solar disk cent…
The Discovery of Cepheids and a Distance to NGC 5128
Ajhar, Edward A.; Stetson, Peter B.; Tonry, John L. +3 more
We discuss a new distance to NGC 5128 (Centaurus A) based on Cepheid variables observed with the Hubble Space Telescope. Twelve F555W (V) and six F814W (I) epochs of cosmic-ray-split WFPC2 observations were obtained. A total of 56 bona fide Cepheids were discovered, with periods ranging from 5 to ~50 days; five of these are likely Population II Ce…
A Connection between Bulge Properties and the Bimodality of Galaxies
Drory, Niv; Fisher, David B.
The global colors and structure of galaxies have recently been shown to follow a bimodal distribution: a ``red sequence'' populated prototypically by early-type galaxies, and a ``blue cloud'' whose typical objects are late-type disk galaxies. Intermediate-type (Sa-Sbc) galaxies populate both regions. It has been suggested that this bimodality refl…
Constraints on Thermal X-Ray Radiation from SAX J1808.4-3658 and Implications for Neutron Star Neutrino Emission
Wijnands, R.; Heinke, C. O.; Jonker, P. G. +1 more
Thermal X-ray radiation from neutron star soft X-ray transients in quiescence provides the strongest constraints on the cooling rates of neutron stars and thus on the interior composition and properties of matter in the cores of neutron stars. We analyze new (2006) and archival (2001) XMM-Newton observations of the accreting millisecond pulsar SAX…
A New Measurement of the Stellar Mass Density at z~5: Implications for the Sources of Cosmic Reionization
Bunker, A. J.; Stark, D. P.; Ellis, R. S. +2 more
We present a new measurement of the integrated stellar mass per comoving volume at redshift 5 determined via spectral energy fitting drawn from a sample of 214 photometrically selected galaxies with z'850LP<26.5 in the southern GOODS field. Following recent procedures introduced by Eyles et al., we estimate stellar masses …
Constraining the Equation of State of Supranuclear Dense Matter from XMM-Newton Observations of Neutron Stars in Globular Clusters
Webb, Natalie A.; Barret, Didier
We report on the detailed modeling of the X-ray spectra of three likely neutron stars. The neutron stars, observed with XMM-Newton, are found in three quiescent X-ray binaries in the globular clusters: ω Cen, M13, and NGC 2808. Whether they are accreting at very low rates or radiating energy from an accretion-heated core, their X-ray spectra are e…
First Space-Based Microlens Parallax Measurement: Spitzer Observations of OGLE-2005-SMC-001
Bennett, D. P.; Griest, K.; Reach, W. T. +20 more
We combine Spitzer and ground-based observations to measure the microlens parallax of OGLE-2005-SMC-001, the first such space-based determination since S. Refsdal proposed the idea in 1966. The parallax measurement yields a projected velocity v∼~230 km s-1, the typical value expected for halo lenses, but an order of magnitude smaller th…
The PN.S Elliptical Galaxy Survey: Data Reduction, Planetary Nebula Catalog, and Basic Dynamics for NGC 3379
Freeman, K. C.; Capaccioli, M.; Napolitano, N. R. +9 more
We present results from Planetary Nebula Spectrograph (PN.S) observations of the elliptical galaxy NGC 3379 and a description of the data reduction pipeline. We detected 214 planetary nebulae, of which 191 are ascribed to NGC 3379 and 23 to the companion galaxy NGC 3384. Comparison with data from the literature shows that the PN.S velocities have …