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The Composition and Distribution of Dust along the Line of Sight toward the Galactic Center
Lutz, D.; van Dishoeck, E. F.; Whittet, D. C. B. +5 more
We discuss the composition of dust and ice along the line of sight to the Galactic center (GC) based on analysis of mid-infrared spectra (2.4-13 µm) from the Short Wavelength Spectrometer on the Infrared Space Observatory (ISO). We have analyzed dust absorption features arising in the molecular cloud material and the diffuse interstellar med…
Intervening O VI Quasar Absorption Systems at Low Redshift: A Significant Baryon Reservoir
Tripp, Todd M.; Jenkins, Edward B.; Savage, Blair D.
Far-UV echelle spectroscopy of the radio-quiet QSO H1821+643 (zem=0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) at ~7 km s-1 resolution, reveals four definite O VI absorption-line systems and one probable O VI absorber at 0.15<zabs<0.27. The four definite O VI absorbers are located nea…
The Hubble Space Telescope Survey of BL Lacertae Objects. II. Host Galaxies
Urry, C. Megan; O'Dowd, Matthew; Scarpa, Riccardo +3 more
We have used the Hubble Space Telescope (HST) WFPC2 camera to survey 132 BL Lac objects comprising seven complete radio-, X-ray-, and optically selected samples. We obtained useful images for 110 targets spanning the redshift range 0<~z<~1.3. These represent an unbiased subsample of the original 132 since they were snapshots selected to fill…
Axisymmetric, Three-Integral Models of Galaxies: A Massive Black Hole in NGC 3379
Gebhardt, Karl; Richstone, Douglas; Kormendy, John +8 more
We fit axisymmetric three-integral dynamical models to NGC 3379 using the line-of-sight velocity distribution obtained from Hubble Space Telescope FOS spectra of the galaxy center and ground-based long-slit spectroscopy along four position angles, with the light distribution constrained by WFPC2 and ground-based images. We have fitted models with …
The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Young Clusters
Luhman, K. L.; Schneider, Glenn; Young, Erick T. +5 more
We have obtained images of the Trapezium Cluster (140''×140'' 0.3 pc×0.3 pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Combining these data with new ground-based K-band spectra (R=800) and existing spectral types and photometry, we have constructed an H-R diagram and used it …
Photochemistry of Saturn's Atmosphere. I. Hydrocarbon Chemistry and Comparisons with ISO Observations
Bézard, Bruno; Lellouch, Emmanuel; Moses, Julianne I. +3 more
To investigate the details of hydrocarbon photochemistry on Saturn, we have developed a one-dimensional diurnally averaged model that couples hydrocarbon and oxygen photochemistry, molecular and eddy diffusion, radiative transfer, and condensation. The model results are compared with observations from the Infrared Space Observatory (ISO) to place …
ISO-SWS spectra of galaxies: Continuum and features
Lutz, D.; Genzel, R.; Sturm, E. +5 more
We present an inventory of mid-infrared spectral features detected in high resolution (R ~ 1500) ISO-SWS 2.4-45mu m spectra of the galaxies
Leptons in near earth orbit
Usoskin, I.; Laitinen, T.; Valtonen, E. +199 more
The lepton spectra in the kinetic energy ranges 0.2 to 40 GeV for e- and 0.2 to 3 GeV for e+ were measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at altitudes near 380km. >From the origin of the leptons two distinct spectra were observed: a higher energy spectrum and a substantial secon…
Rigidity dependence of cosmic ray proton latitudinal gradients measured by the Ulysses spacecraft: Implications for the diffusion tensor
Potgieter, M. S.; Heber, B.; Burger, R. A.
The latitudinal gradient of cosmic ray protons observed by Ulysses during September 1994 to July 1995 is small, and it increases as function of rigidity up to ~2 GV and then decreases. Although previous drift models could reproduce the observed small positive gradient for an A>0 solar polarity cycle, they produced a maximum at a rigidity well b…
A Lack of Planets in 47 Tucanae from a Hubble Space Telescope Search
Edmonds, P. D.; Cochran, W. D.; Sarajedini, A. +21 more
We report results from a large Hubble Space Telescope project to observe a significant (~34,000) ensemble of main-sequence stars in the globular cluster 47 Tucanae with a goal of defining the frequency of inner orbit, gas giant planets. Simulations based on the characteristics of the 8.3 days of time series data in the F555W and F814W Wide Field P…