Search Publications
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 …
A Strong Correlation between Circumnuclear Dust and Black Hole Accretion in Early-Type Galaxies
Storchi-Bergmann, Thaisa; Simões Lopes, Ramiro D.; de Fátima Saraiva, Maria +1 more
We present a detailed investigation of the incidence of circumnuclear dust structure in a large, well-matched sample of early-type galaxies with and without active galactic nuclei (AGNs). All 34 early-type AGN hosts in our sample have circumnuclear dust, while dust is only observed in 26% (9) of a pair-matched sample of 34 early-type, inactive gal…
Constraints on Neutron Star Properties from X-Ray Observations of Millisecond Pulsars
Bogdanov, Slavko; Grindlay, Jonathan E.; Rybicki, George B.
We present a model of thermal X-ray emission from hot spots on the surface of a rotating compact star with an unmagnetized light-element atmosphere. An application to ROSAT, Chandra, and XMM-Newton X-ray observations of the nearest known rotation-powered millisecond pulsar (MSP) PSR J0437-4715 reveals that the thermal emission from this pulsar is …
Characterization of Gravitational Microlensing Planetary Host Stars
Anderson, Jay; Gaudi, B. Scott; Bennett, David P.
The gravitational microlensing light curves that reveal the presence of extrasolar planets generally yield the planet-star mass ratio and separation in units of the Einstein ring radius. The microlensing method does not require the detection of light from the planetary host star. This allows the detection of planets orbiting very faint stars, but …
Nonthermal Velocities in Solar Active Regions Observed with the Extreme-Ultraviolet Imaging Spectrometer on Hinode
Young, P. R.; Mason, H. E.; Culhane, J. L. +6 more
We discuss nonthermal velocities in an active region as revealed by the Extreme-Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. The velocities are derived from spectral line profiles in the extreme-ultraviolet (EUV) from a strong line of Fe XII at 195.12 Å by fitting each line profile to a Gaussian function. We compare maps of the…