Search Publications
An Empirical Ultraviolet Template for Iron Emission in Quasars as Derived from I Zwicky 1
Vestergaard, M.; Wilkes, B. J.
We present an empirical template spectrum suitable for fitting and subtracting/studying the Fe II and Fe III emission lines in the rest frame ultraviolet spectra of quasars and active galactic nuclei, the first empirical ultraviolet iron template to cover the full range of 1250-3090 Å. Iron emission is often a severe contaminant in optical-ultravi…
The Distribution of Thermal Pressures in the Interstellar Medium from a Survey of C I Fine-Structure Excitation
Tripp, Todd M.; Jenkins, Edward B.
We used the Space Telescope Imaging Spectrograph (STIS) with its smallest entrance aperture (0.03" wide slit) and highest resolution echelle gratings (E140H and E230H) to record the interstellar absorption features for 10 different multiplets of neutral carbon at a resolving power of λ/Δλ=200,000 in the UV spectra of 21 early-type stars. Our objec…
CHIANTI-An Atomic Database for Emission Lines. IV. Extension to X-Ray Wavelengths
Young, P. R.; Del Zanna, G.; Dere, K. P. +1 more
CHIANTI provides a database of atomic energy levels, wavelengths, radiative transition probabilities, and electron excitation data for a large number of ions of astrophysical interest. It also includes a suite of Interactive Data Language programs to calculate optically thin synthetic spectra and to perform spectral analysis and plasma diagnostics…
NICMOS Observations of High-Redshift Radio Galaxies: Witnessing the Formation of Bright Elliptical Galaxies?
Pentericci, L.; Fosbury, R.; Röttgering, H. J. A. +3 more
We present the results of a near-infrared imaging program of a sample of 19 radio galaxies with redshift between 1.7 and 3.2, using the NICMOS Camera 2 on the Hubble Space Telescope (HST). The galaxies were observed in H band, which, for 18 of the 19 targets, samples the rest-frame optical emission longward of the 4000 Å break. For many sources th…
The MACHO Project: Microlensing Detection Efficiency
Alcock, C.; Allsman, R. A.; Alves, D. R. +21 more
The MACHO project is a search for dark matter in the form of massive compact halo objects (MACHOs). The project has photometrically monitored over forty million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and Galactic bulge in search of rare gravitational microlensing events caused by these otherwise invisible objects.…
A Search for Signatures of Quasar Evolution: Comparison of the Shapes of the Rest-Frame Optical/Ultraviolet Continua of Quasars at z>3 and z~0.1
Elvis, Martin; Bechtold, Jill; Elston, Richard +1 more
For 15 bright (V<17.5), high-redshift (z>3) quasars, we have obtained infrared spectra and photometry, and optical spectrophotometry and photometry, which we use to construct their spectral energy distributions (SEDs) from λrest~1285-5100 Å. High-resolution spectroscopy for seven enable measurements of their continua shortward of …
IUE Absorption-Line Observations of the Moderately and Highly Ionized Interstellar Medium toward 164 Early-Type Stars
Sembach, Kenneth R.; Savage, Blair D.; Meade, Marilyn R.
We present measurements of Galactic interstellar Al III, Si IV, and C IV absorption recorded in high-resolution archival ultraviolet spectra of 164 hot early-type stars observed by the International Ultraviolet Explorer (IUE) satellite. The objects studied were drawn from the list of hot stars scheduled to be observed with the Far Ultraviolet Spec…
Physical Conditions in the Foreground Gas of Reflection Nebulae: NGC 2023, vdB 102, and NGC 7023
Federman, S. R.; Lambert, David L.; Yan, M. +2 more
High-resolution optical spectra of HD 37903 and HD 147009, which illuminate the reflection nebulae NGC 2023 and vdB 102, were obtained for comparison with our results for HD 200775 and NGC 7023. Ground-based measurements of the molecules CH, C2, and CN and the atoms Na I and K I were analyzed to extract physical conditions in the foregr…
New Rest Wavelength Determinations for Seven Mid-Infrared Fine-Structure Lines by ISO-SWS
Lutz, D.; Beintema, D. A.; Feuchtgruber, H.
Observations of the planetary nebulae NGC 6302, NGC 6543, and NGC 7027 by the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO) have been used to determine rest wavelengths of spectral lines. We report on improved accuracies for wavelengths of seven mid-infrared ionic fine-structure lines. Based on observations made…
Emission-Line Ratios for [N II] in Gaseous Nebulae and a Comparison between Theory and Observation
Feibelman, W. A.; Keenan, F. P.; Aller, L. H. +1 more
R-matrix calculations of electron impact excitation rates among the 2s22p2 3P, 1D, 1S, and 2s2p3 5S levels of N II are presented. These results are used in conjunction with other recent calculations of electron impact excitation rates and Einstein A-coefficients for N II …