Search Publications
Measurements of the Cosmological Parameters Ω and Λ from the First Seven Supernovae at z >= 0.35
Filippenko, A. V.; Goldhaber, G.; Goobar, A. +21 more
We have developed a technique to systematically discover and study high-redshift supernovae that can be used to measure the cosmological parameters. We report here results based on the initial seven of more than 28 supernovae discovered to date in the high-redshift supernova search of the Supernova Cosmology Project. We find an observational dispe…
Evolution since z = 0.5 of the Morphology-Density Relation for Clusters of Galaxies
Smail, Ian; Ellis, Richard S.; Dressler, Alan +6 more
Using traditional morphological classifications of galaxies in 10 intermediate-redshift (z ~ 0.5) clusters observed with WFPC2 on the Hubble Space Telescope, we derive relations between morphology and local galaxy density similar to that found by Dressler for low-redshift clusters. Taken collectively, the ``morphology-density'' relationship, T - Σ…
Measurements of Flow Speeds in the Corona Between 2 and 30 R⊙
Llebaria, A.; St. Cyr, O. C.; Michels, D. J. +16 more
Time-lapse sequences of white-light images, obtained during sunspot minimum conditions in 1996 by the Large Angle Spectrometric Coronagraph on the Solar and Heliospheric Observatory, give the impression of a continuous outflow of material in the streamer belt, as if we were observing Thomson scattering from inhomogeneities in the solar wind. Pursu…
A Composite HST Spectrum of Quasars
Kriss, Gerard A.; Zheng, Wei; Davidsen, Arthur F. +2 more
We construct a composite quasar spectrum from 284 HST FOS spectra of 101 quasars with redshifts z > 0.33. The spectrum covers the wavelengths between 350 and 3000 Å in the rest frame, with a peak S/N level of ~130 per Å at ~1200 Å. Since ~90% of the sample quasars have redshift z < 1.5, the spectrum is suitable for studying the wavelength re…
Hubble Space Telescope Images of a Sample of 20 Nearby Luminous Quasars
Schneider, Donald P.; Bahcall, John N.; Kirhakos, Sofia +1 more
Observations with the Wide-Field Camera of the Hubble Space Telescope (HST) are presented for a representative sample of 20 intrinsically luminous quasars with redshifts smaller than 0.30. These observations show that luminous quasars occur in diverse environments that include ellipticals as bright as the brightest cluster galaxies (two), apparent…
Keck Spectroscopy of Redshift z ~ 3 Galaxies in the Hubble Deep Field
Illingworth, Garth D.; Faber, S. M.; Gronwall, Caryl +6 more
We have obtained spectra with the 10 m Keck telescope of a sample of 24 galaxies having colors consistent with star-forming galaxies at redshifts 2 <~ z <~ 4.5 in the Hubble deep field (HDF). Eleven of these galaxies are confirmed to be at high redshift (zmed = 3.0), one is at z = 0.5, and the other 12 have uncertain redshifts but…
The Homogeneity of Spheroidal Populations in Distant Clusters
Smail, Ian; Ellis, Richard S.; Dressler, Alan +4 more
The small scatter observed for the (U-V) colors of spheroidal galaxies in nearby clusters of galaxies provides a powerful constraint on the history of star formation in dense environments. However, with local data alone, it is not possible to separate models where galaxies assembled synchronously over redshifts 0 < z < 1 from ones where gala…
The Evolution of the Global Star Formation History as Measured from the Hubble Deep Field
Dickinson, Mark; Connolly, A. J.; Szalay, A. S. +2 more
The Hubble Deep Field (HDF) is the deepest set of multicolor optical photometric observations ever undertaken, and it offers a valuable data set with which to study galaxy evolution. Combining the optical WFPC2 data with ground-based near-infrared photometry, we derive photometrically estimated redshifts for HDF galaxies with J < 23.5. We demon…
The Supermassive Black Hole of M87 and the Kinematics of Its Associated Gaseous Disk
Marconi, A.; Capetti, A.; Crane, P. +3 more
We have obtained long-slit observations of the circumnuclear region of M87 at three different locations, with a spatial sampling of 0.028" using the Faint Object Camera f/48 spectrograph on board HST. These data allow us to determine the rotation curve of the inner ~1" of the ionized gas disk in [O II] λ3727 to a distance as close as 0.07" (~=5 pc…
LBDS 53W091: An Old, Red Galaxy at z = 1.552
Windhorst, Rogier; Dey, Arjun; Spinrad, Hyron +4 more
The weak radio source LBDS 53W091 is associated with a very faint (R ~ 24.5) red (R - K ~ 5.8) galaxy. Long spectroscopic integrations with the W. M. Keck telescope have provided an absorption-line redshift, z = 1.552 +/- 0.002. The galaxy has a rest frame ultraviolet spectrum very similar to that of an F6 V star, and a single-burst old stellar po…