Search Publications
RX J0911+05: A Massive Cluster Lens at z=0.769
Kneib, Jean-Paul; Hjorth, Jens; Cohen, Judith G.
We report the detection of a massive high-redshift cluster of galaxies near the quadruple quasar RX J0911+05, using the Low-Resolution Imaging Spectrograph instrument on the Keck II telescope. The cluster is found to have a mean redshift of z=0.7689+/-0.002 and a velocity dispersion of σ=836+180-200 km s-1, based o…
Signatures of the Rise of Cycle 23
Kosovichev, A. G.; Schou, J.; Dziembowski, W. A. +1 more
During the rise of Cycle 23, we have found a sizable, systematic evolution of the Solar and Heliospheric Observatory/Michelson Doppler Imager solar oscillation frequencies implying significant changes in the spherically symmetric structure of the Sun's outer layers as well as in its asphericity up to a P18 Legendre distortion. We conduc…
Seeing Galaxies through Thick and Thin. I. Optical Opacity Measures in Overlapping Galaxies
Conselice, Christopher J.; White, Raymond E., III; Keel, William C.
We describe the use of partially overlapping galaxies to provide direct measurements of the effective absorption in galaxy disks, independent of assumptions about internal disk structure. The nonoverlapping parts of the galaxies and symmetry considerations are used to reconstruct, via differential photometry, how much background galaxy light is lo…
On the Emergence and Discovery of Hot Spots in SNR 1987A
Crotts, Arlin P. S.; Lawrence, Stephen S.; Heathcote, Steve +3 more
We present the discovery of several new regions of interaction between the ejecta and equatorial circumstellar ring of SN 1987A, an interaction leading to a much-expanded development of the supernova remnant. We also trace the development of the first such ``hot spot,'' discovered in 1997, back to 1995. Later hot spots seem to have emerged by earl…
On the Helium Content of Galactic Globular Clusters via the R-Parameter
Djorgovski, S. G.; Zoccali, M.; Rich, R. M. +3 more
We estimate the empirical R-parameter in 26 Galactic globular clusters covering a wide metallicity range, imaged by Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The improved spatial resolution permits a large fraction of evolved stars to be measured and permits accurate assessment of radial population gradients and completene…
Water in Emission in the Infrared Space Observatory Spectrum of the Early M Supergiant Star µ Cephei
Tsuji, Takashi
We report a detection of water in emission in the spectrum of the M2 supergiant star µ Cephei (M2 Ia) observed by the Short-Wavelength Spectrometer on board Infrared Space Observatory (ISO) and now released in the ISO archives. The emission first appears in the 6 µm region (ν2 fundamental bands) and then in the 40 µm r…
Young Stellar Populations around SN 1987A
Kirshner, Robert P.; Panagia, Nino; Romaniello, Martino +1 more
We present the first results of a study of the stellar population in a region of 30 pc radius around SN 1987A, based on an analysis of multiband Hubble Space Telescope (HST) WFPC2 images. The effective temperature, radius and, possibly, reddening of each star were determined by fitting the measured broadband magnitudes to the ones calculated with …
The Host Galaxy of the Lensed Quasar Q0957+561
Peng, C. Y.; Keeton, C. R.; Kochanek, C. S. +6 more
Infrared images of the Q0957+561 gravitational lens obtained with the Hubble Space Telescope show two large (~5") lensed images of the zs=1.41 quasar host galaxy. Parts of the host galaxy are doubly imaged, like the quasar, while other parts are quadruply imaged. The distortions of the host galaxy offer the best probe yet of the global …
On the Constancy of the Solar Diameter
Kuhn, J. R.; Bush, R. I.; Emilio, M. +1 more
Why does the solar luminosity vary and could it change on human timescales by enough to affect terrestrial climate? As important as these questions are, we lack answers because we do not understand the physical mechanisms responsible for the solar irradiance cycle. Progress here depends on discovering how changes in the solar interior affect energ…
Development of Coronal Mass Ejections: Radio Shock Signatures
Vourlidas, Angelos; Howard, Russel; Pick, Monique +1 more
We present observational imaging evidence for the existence of metric radio bursts closely associated with the front edge of coronal mass ejections (CMEs). These radio bursts drift in frequency similarly to type II bursts. They are weak and usually go undetected on spectrograph data. We find the same measured projected velocity for the displacemen…