Search Publications
The Metallicity of Low-Redshift Lyalpha Forest Clouds
Tytler, David; Barlow, Thomas A.
Using archival Hubble Space Telescope (HST) Faint Object Spectrograph spectra of 15 quasars, we measure an average metallicity for Lyalpha forest absorption clouds between redshifts of 0.3 and 0.8. A composite spectrum of all Lyalpha systems shows an average rest equivalent width of ~0.06 Å for C iv lambda1548.20. This is a factor of 10 larger tha…
Accuracy of Current Density Determination
Robert, Patrick; Dunlop, Malcolm W.; Roux, Alain +1 more
Cassini uvis observations of Saturns rings
Colwell, Joshua E.; Esposito, Larry W.; McClintock, William E.
The Cassini Ultra-violet Imaging Spectrograph (UVIS) is part of the remote sensing payload of the Cassini Orbiter spacecraft. Its science objectives include investigation of the chemistry, clouds, and energy balance of the Titan and Saturn atmospheres ; neutrals in the magnetosphere ; D/H ratio for Titan and Saturn ; and structure and evolution of…
Spectral analysis of the high-gravity extreme helium star LSIV+6 deg2
Jeffery, C. S.
The optical spectrum of the early B hydrogen-deficient star LSIV+6 deg2 has been analysed. With T_eff=31000K, logg=4.05, n_H~10^-4 and n_c~0.1 (relative abundances by number), it is the hottest high-gravity extreme helium star (EHe) yet studied. The Hei spectrum shows all predicted permitted and forbidden transitions in absorption. LSIV+6 deg2 is …
Detection of further UV-bright high-redshift QSOs
Reimers, D.; Hagen, H. -J.; Rodriguez-Pascual, P. +1 more
We present successful UV observations with IUE of several newly discovered high-redshift QSOs from the Hamburg QSO Surveys. In addition to three previously discovered QSOs three new objects have been found to have lines of sight transparent to wavelengths as short as 1200 { Angstroms}: HS 0747+4259 (z = 1.9, V = 15.8); HS 1147+6556 (z = 2.21, V = …
Early-Type Galaxies in the Hubble Deep Field: The <mu_e>-r_e Relation and the Lack of Large Galaxies at High Redshift
Fasano, Giovanni; Cristiani, Stefano; Arnouts, Stephane +1 more
We present the results of detailed surface photometry of a sample of early-type galaxies in the Hubble Deep Field (HDF). Effective radii, surface brightnesses, and total V_606 magnitudes have been obtained, as well as U_300, B_450, I_814, J, H, and K colors, which are compared with the predictions of chemical spectrophotometric models of populatio…
Luminosity Functions for Globular Clusters
D'Antona, Francesca; Ventura, Paolo; Silvestri, Fabio +1 more
We present theoretical mass-luminosity relations and luminosity functions (LFs) for globular cluster stars, from luminosities above the horizontal branch down to the minimum luminosity of hydrogen-burning stars. The LFs are available for metal mass fraction Z from Z = 10-4 to Z = 4 × 10-3, in the Johnson V band and in the Bes…
The Geometric Spreading of Coronal Plumes and Coronal Holes
Wu, S. T.; Poletto, G.; Suess, S. T. +2 more
The geometric spreading in plumes and in the interplume region in coronal holes is calculated, using analytic and numerical theoretical models, between 1.0 and 5.0 R⊙. We apply a two-scale approximation that permits the rapid local spreading at the base of plumes (fl) to be evaluated separately from the global spreading (f
High-Velocity Lyα Emission from SNR 1987A
Pun, Chun S. J.; Sonneborn, George; Borkowski, Kazimierz J. +2 more
The high-velocity Lyα emission from SN 1987A observed with the Space Telescope Imaging Spectrograph (STIS) evidently comes from a reverse shock formed where the outer envelope of SN 1987A strikes ionized gas inside the inner circumstellar ring. The observations can be explained by a simple kinematic model, in which the Lyα emission comes from hydr…
Global Context of the Galileo-E6 Observations of Jupiter's White Ovals
Simon, Amy A.; Belton, Michael J. S.; Gierasch, Peter J. +3 more
Galileo Solid State Imaging (SSI) data taken during the E6 orbit on February 19, 1997 offer a brief, high-resolution glimpse of Jupiter's White Ovals. These data can be used to infer relative cloud heights and systematic rotations over a small area of latitude and longitude (approximately 20° by 30°) around the White Ovals. To fully understand the…