Search Publications
The Relationship between the High-Energy Continuum and Emission Lines in Quasars: A Low-Redshift Sample
Green, Paul J.
Photoionization models dictate that many prominent quasar emission lines are sensitive to both the luminosity and shape of the quasars high- energy continuum-primarily the extreme ultraviolet (EUV) and soft X-ray continuum. Unfortunately, the EUV band is severely obscured by Galactic absorption. Using data from the adjacent UV and soft X-ray bandp…
Far-Ultraviolet Spectra of Broad Absorption Line QSOs and Constraints on Models for the Ionization Structure and Metallicity of the BAL-Region Gas
Turnshek, David A.; Weymann, Ray J.; Kopko, Michael, Jr. +3 more
Hubble Space Telescope Faint Object Spectrograph G270H spectra of four moderate-to high-redshift broad absorption line (BAL) QSOs are presented. In addition, evidence is discussed that indicates that the gas that gives rise to the BALs has nonuniform ionization and enhanced abundances. In the context of a photoionization model, ionization paramete…
The Elemental Composition of the Galactic Cosmic-Ray Source: ULYSSES High-Energy Telescope Results
Duvernois, M. A.; Thayer, M. R.
The nucleosynthetic origin of the galactic cosmic-ray sources (GCRS) is a matter of some considerable interest (e.g., Leske; Connell & Simpson; DuVernois et al.). Any understanding of this origin requires an accurate determination of the source elemental abundances. These abundances are determined by comparing the Ulysses High-Energy Telescope…
Biconical Radiation Field and Outflow in NGC 1068: Location of the Hidden Nucleus
Arribas, S.; Mediavilla, E.; Garcia-Lorenzo, B.
Bidimensional spectroscopy of the circumnuclear region (central 10" x 8") of the Seyfert 2 galaxy NGC 1068 has been performed by means of an optical fiber system. The 95 spectra obtained simultaneously include the [N II] λλ6548, 6583, Hα, and [S II] λλ6716,6731 emission lines. In the inner regions, the velocity field obtained by cross-correlating …
The Composition of the Diffuse Interstellar Medium
Fitzpatrick, Edward L.
Recent Goddard High Resolution Spectrograph measurements of Si, S, Cr, Mn, Fe, and Zn in interstellar clouds along lines of sight in the Galactic disk and into the lower halo are discussed. The gas-phase abundance of S relative to H in the interstellar clouds appears to be indistinguishable from the solar value. For the other elements, we find wel…
Discovery of Photospheric Sulfur and Phosphorus in ORFEUS Spectra of the Hot White Dwarfs G191-B2B and MCT O455-2812
Bowyer, Stuart; Vennes, Stephane; Chayer, Pierre +1 more
High-dispersion observations of the far-ultraviolet (FUV) spectra of the hot DA white dwarfs G191-B2B and MCT 0455-2812 reveal the presence of two previously undetected elements in white dwarf photospheres: sulfur and phosphorus. The spectra, obtained with the Berkeley EUV/FUV spectrometer and the ORFEUS telescope aboard the space platform Astro-S…
Physical Conditions in Low Ionization Regions of the Orion Nebula
Martin, P. G.; Crotts, A.; O'Dell, C. R. +12 more
We reexamine the spectroscopic underpinnings of recent suggestions that [O I] and [Fe II] lines from the Orion H II region are produced in gas where the iron-carrying grains have been destroyed and the electron density is surprisingly high. Our new observations show that previous detections of [O I] 5577 were dominated by telluric emission. Our li…
Luminosity Functions of Elliptical Galaxies at Z <1.2
Im, Myungshin; Griffiths, Richard E.; Ratnatunga, Kavan U. +1 more
The luminosity functions of E/S0 galaxies are constructed in three different redshift bins (0.2 < z < 0.55, 0.55 < z < 0.8, 0.8 < z < 1.2), using the data from the Hubble Space Telescope (HST) Medium Deep Survey and other HST surveys. These independent luminosity functions show the brightening in the luminosity of E/S0s by about …
Intercombinations and Allowed Transitions in O IV
Judge, P. G.; Brekke, P.; Brage, Tomas
We report on large-scale ab initio multiconfiguration Hartree-Fock calculations for important multiplets including the UV 0.01 multiplet, 2s22p2PJ-2s2p2 4Pj', in O IV. The resulting transition probabilities should be accurate to ±5%-10% for intersystem lines and 1% or better for per…
On the Nature of the Outer Rings around SN 1987A
Panagia, N.; Kirshner, R. P.; Garnavich, P. M. +3 more
We present recent Hubble Space Telescope (HST) Faint Object Spectrograph and ground-based spectroscopic observations of SN 1987A and its surroundings and discuss them in conjunction with HST Faint Object Camera and Wide Field Planetary Camera 2 narrowband imaging. We have determined the following properties of the outer rings around SN 1987A: (1) …