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Far-Ultraviolet Spectroscopy of the Intergalactic and Interstellar Absorption toward 3C 273
Sembach, Kenneth R.; Savage, Blair D.; Shull, J. Michael +2 more
We present Far Ultraviolet Spectroscopic Explorer observations of the molecular, neutral atomic, weakly ionized, and highly ionized components of the interstellar and intergalactic material toward the quasar 3C 273. We identify Lyβ absorption in eight of the known intergalactic Lyα absorbers along the sight line with rest-frame equivalent widths W…
Heavy X-Ray Absorption in Soft X-Ray-weak Active Galactic Nuclei
Brandt, W. N.; Elvis, M.; Gallagher, S. C. +4 more
Recent ROSAT studies have identified a significant population of active galactic nuclei (AGNs) that are notably faint in soft X-rays relative to their optical fluxes. Are these AGNs intrinsically X-ray weak or are they highly absorbed? Brandt, Laor, & Wills have systematically examined the optical and UV spectral properties of a well-defined s…
The Resolved Stellar Populations in NGC 1705
Leitherer, Claus; Greggio, L.; Tosi, M. +4 more
We present HST photometry of the resolved stellar population in the dwarf irregular galaxy NGC 1705. The galaxy has been observed with both WFPC2 and NICMOS, and successful images have been obtained in the F555W, F814W, F110W, and F160W bands. The optical fields cover most of the galaxy, while the infrared field (NIC2) maps only its central region…
Cluster as a wave telescope - first results from the fluxgate magnetometer
Balogh, A.; Glassmeier, K. -H.; Buchert, S. +9 more
The four Cluster spacecraft provide an excellent opportunity to study spatial structures in the magnetosphere and adjacent regions. Propagating waves are amongst the interesting structures and for the first time, Cluster will allow one to measure the wave vector of low-frequency fluctuations in a space plasma. Based on a generalized minimum varian…
A Spatially Resolved, Semiempirical Model for the Extended Atmosphere of α Orionis (M2 Iab)
Harper, Graham M.; Brown, Alexander; Lim, Jeremy
We have constructed a detailed mean density and temperature model for the extended outer atmosphere of the O-rich supergiant Betelgeuse (α Ori [M2 Iab]), which extends from 1.0 to 10.0 stellar radii. A one-dimensional model is based on fitting NRAO1 VLA centimeter visibility data, and two-dimensional models are constructed using the intensity cont…
Oxygen in the Very Early Galaxy
Basri, Gibor; Israelian, Garik; Rebolo, Rafael +4 more
Oxygen abundances in a sample of ultra-metal-poor subdwarfs have been derived from measurements of the oxygen triplet at 7771-5 Å and OH lines in the near-UV performed in high-resolution and high signal-to-noise ratio spectra obtained with WHT/UES, Keck I/HIRES, and VLT/UVES. Our Fe abundances were derived in LTE and then corrected for non-LTE (NL…
The star cluster system of the 3-Gyr-old merger remnant NGC 1316: clues from optical and near-infrared photometry
Minniti, Dante; Maraston, Claudia; Goudfrooij, Paul +1 more
The giant merger remnant galaxy NGC 1316 (Fornax A) is an ideal probe for studying the long-term effects of a past major merger on star cluster systems, given its spectroscopically derived merger age of ~3Gyr which we reported in a recent paper. Here we present new ground-based, large-area optical and near-IR imaging of star clusters in NGC 1316. …
The Redshift and the Ordinary Host Galaxy of GRB 970228
Bloom, J. S.; Djorgovski, S. G.; Kulkarni, S. R.
The gamma-ray burst of 1997 February 28 (GRB 970228) ushered in the discovery of the afterglow phenomenon. Despite intense study of the nearby galaxy, however, the nature of this galaxy and the distance to the burst eluded the community. Here we present the measurement of the redshift of the galaxy, the putative host galaxy of GRB 970228, and, bas…
Helium-like triplet density diagnostics. Applications to CHANDRA-LETGS X-ray observations of Capella and Procyon
Schmitt, J. H. M. M.; Kaastra, J. S.; Burwitz, V. +6 more
Electron density diagnostics based on the triplets of helium-like C v, N vi, and O vii are applied to the X-ray spectra of Capella and Procyon measured with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra X-ray Observatory. New theoretical models for the calculation of the line ratios between the forbidden (f), interc…
Cusped Mass Models of Gravitational Lenses
Keeton, C. R.; Kochanek, C. S.; Muñoz, J. A.
Recent observations of galaxy luminosity profiles and dark matter simulations find luminosity and mass distributions characterized by central cusps rather than finite core radii. We introduce and implement a set of cusped ellipsoidal lens models that include limits similar to the Jaffe, Hernquist, η and NFW models and apply them to the gravitation…