Search Publications
Infrared Space Observatory Long Wavelength Spectrometer Observations of a Cold Giant Molecular Cloud Core near the Galactic Center
Menten, Karl M.; Lis, D. C.
We have used the Long Wavelength Spectrometer aboard the Infrared Space Observatory in the grating mode to map the far-infrared continuum emission (45-175 µm) toward the massive giant molecular cloud core GCM 0.25+0.11 located near the Galactic center. Graybody models of the observed far-infrared spectral energy distribution indicate that th…
Jet-induced Shocks in 3C 171: An Intermediate-Redshift Analog of High-Redshift Radio Galaxies
Tadhunter, C. N.; Axon, D. J.; Robinson, A. +2 more
We present spectroscopic observations of the extended emission-line region (EELR) aligned with the radio axis of the powerful radio galaxy 3C 171. The results obtained from a detailed analysis of the observational data show that shocks induced by jet-cloud interactions have a dramatic effect on the extended line-emitting gas. The evidence for shoc…
Hyperfine Induced Transitions as Diagnostics of Isotopic Composition and Densities of Low-Density Plasmas
Judge, Philip G.; Jönsson, Per; Brage, Tomas +5 more
The J = 0 --> J' = 0 radiative transitions, usually viewed as allowed through two-photon decay, may also be induced by the hyperfine (HPF) interaction in atoms or ions having a nonzero nuclear spin. We compute new and review existing decay rates for the nsnp 3PoJ --> ns2 1SJ'=0
Reobservation of Close QSO Groups: The Size Evolution and Shape of Lyα Forest Absorbers
Crotts, Arlin P. S.; Fang, Yihu
In order to study the size and shape of the absorbers that lie in front of the QSOs, in particular the Lyα forest, we present an analysis of 785 absorption lines in the spectra of five QSOs in close groupings: a pair (LB 9605: 1517+2357 at z = 1.834 and LB 9612: 1517+2356 at z = 1.903, with a separation of 102" between them) and a triplet (KP 76: …
The Local ISM and Its Interaction with the Winds of Nearby Late-Type Stars
Wood, Brian E.; Linsky, Jeffrey L.
We present new Goddard High-Resolution Spectrograph (GHRS) observations of the Lyα and Mg II absorption lines seen toward the nearby stars 61 Cyg A and 40 Eri A. We use these data to measure interstellar properties along these lines of sight and to search for evidence of circumstellar hydrogen walls, which are produced by collisions between the st…
Dust Spirals and Acoustic Noise in the Nucleus of the Galaxy NGC 2207
Elmegreen, B. G.; Brinks, E.; Elmegreen, D. M. +6 more
Observations with the Hubble Space Telescope reveal an irregular network of dust spiral arms in the nuclear region of the interacting disk galaxy NGC 2207. The spirals extend from ~50 to ~300 pc in galactocentric radius, with a projected width of ~20 pc. Radiative transfer calculations determine the gas properties of the spirals and the inner disk…
The ISO-SWS 2.4-45.2 Micron Spectrum Toward Orion IR c2
Cernicharo, José; Vandenbussche, Bart; van Dishoeck, Ewine F. +4 more
The complete infrared spectrum from 2.4 to 45.2 µm toward the prototypical massive star-forming region Orion IRc2 is presented, obtained with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO) at a resolving power λ/Δλ~1300-2500. A wealth of emission and absorption features is found, including H2…
Boron in Very Metal Poor Stars
Lambert, David L.; Edvardsson, Bengt; Rebolo, Rafael +3 more
We have observed the B I 2497 A line to derive the boron abundances of two very metal-poor stars selected to help in tracing the origin and evolution of this element in the early Galaxy: BD +23 3130 and HD 84937. The observations were conducted using the Goddard High Resolution Spectrograph on board the Hubble Space Telescope. A very detailed abun…
Hubble Space Telescope WFPC2 Color-Magnitude Diagrams of Halo Globular Clusters in M33: Implications for the Early Formation History of the Local Group
Sarajedini, Ata; Schommer, Robert; Geisler, Doug +1 more
We have constructed color-magnitude diagrams for 10 globular clusters in the halo of the nearby spiral galaxy M33 based on Hubble Space Telescope Wide Field Planetary Camera 2 observations in the F555W (~V) and F814W (~I) filters. These data reveal the morphology of the horizontal branch (HB) and allow us to estimate the cluster metallicity using …
Anomalous Cooling of the Massive White Dwarf in U Geminorum Following a Narrow Dwarf Nova Outburst
Szkody, Paula; Sion, Edward M.; Cheng, F. H. +4 more
We obtained Hubble Space Telescope Goddard High-Resolution Spectrograph medium-resolution (G160M grating), phase-resolved spectroscopic observations of the prototype dwarf nova U Geminorum during dwarf nova quiescence, 13 days and 61 days following the end of a narrow outburst. The spectral wavelength ranges were centered on three different line r…