Search Publications
Elemental composition of the inner source pickup ions
Geiss, J.; Schwadron, N. A.; Zurbuchen, T. H. +2 more
Observations of the composition of inner source pickup ions in the solar wind, from the Solar Wind Ion Composition Spectrometer on Ulysses, are presented. The composition is similar to that of the solar wind and, in particular, contains volatile elements such as neon. These observations suggest strongly, and perhaps conclusively, that inner source…
The ortho:para-H_2 ratio in C- and J-type shocks
Pineau des Forêts, G.; Cabrit, S.; Flower, D. R. +1 more
We have computed extensive grids of models of both C- and J-type planar shock waves, propagating in dark, cold molecular clouds, in order to study systematically the behaviour of the ortho:para-H_2 ratio. Careful attention was paid to both macroscopic (dynamical) and microscopic (chemical reactions and collisional population transfer in H_2) aspec…
Spatial Variability in the Ratio of Interstellar Atomic Deuterium to Hydrogen. II. Observations toward γ2 Velorum and ζ Puppis by the Interstellar Medium Absorption Profile Spectrograph
Tripp, Todd M.; Jenkins, Edward B.; Vidal-Madjar, Alfred +4 more
High-resolution far-ultraviolet spectra of the early-type stars γ2 Vel and ζ Pup were obtained to measure the interstellar deuterium abundances in these directions. The observations were made with the Interstellar Medium Absorption Profile Spectrograph (IMAPS) during the ORFEUS-SPAS II mission in 1996. IMAPS spectra cover the wavelength…
Mid-infrared ISO spectroscopy of NGC 4945
Lutz, D.; Tielens, A. G. G. M.; Moorwood, A. F. M. +2 more
We have observed the central region of the nearby starburst galaxy NGC 4945 with the mid-infrared spectrometers SWS and PHT-S aboard ISO. We do not find any evidence for the existence of the powerful AGN, inferred from hard X-ray observations. The upper limits on our AGN tracers [ion {Ne}{v}] 14.32 mu m&24.3 mu m and [ion {Ne}{vi}] 7.65 mu m i…
Infrared imaging and spectroscopy of the Luminous Blue Variables Wra 751 and AG Car
Waters, L. B. F. M.; Morris, P. W.; Barlow, M. J. +6 more
We present ground-based infrared imaging and ISO spectroscopy of the luminous blue variables Wra 751 and AG Car. The images show in both cases a detached shell with a roughly circular distribution of emission. The infrared images of AG Car coincide very well with the optical images. The optical (Hα ) image of Wra 751 is different from the infrared…
Infrared observations of hot gas and cold ice toward the low mass protostar Elias 29
de Graauw, Th.; Ceccarelli, C.; van Dishoeck, E. F. +5 more
We have obtained the full 1-200 µm spectrum of the low luminosity (36 Lsolar) Class I protostar Elias 29 in the ρ Ophiuchi molecular cloud. It provides a unique opportunity to study the origin and evolution of interstellar ice and the interrelationship of interstellar ice and hot core gases around low mass protostars. We see abund…
Gravitational Lensing of Distant Supernovae in Cold Dark Matter Universes
Madau, Piero; Porciani, Cristiano
Ongoing searches for supernovae (SNe) at cosmological distances have recently started to provide large numbers of events with measured redshifts and apparent brightnesses. Compared to quasars or galaxies, Type Ia SNe represent a population of sources with well-known intrinsic properties and could be used to detect gravitational lensing even in the…
B Stars as a Diagnostic of Star Formation at Low and High Redshift
Heckman, Timothy M.; Leitherer, Claus; de Mello, Duília F.
We have extended the evolutionary synthesis models by Leitherer et al. by including a new library of B stars generated from the IUE high-dispersion spectra archive. We present the library and show how the stellar spectral properties vary according to luminosity classes and spectral types. We have generated synthetic UV spectra for prototypical you…
Hipparcos parallaxes for Mira-like long-period variables
Feast, Michael; Whitelock, Patricia
This paper concerns the calibration of the K period-luminosity relation for Mira variables using Hipparcos parallaxes. K magnitudes are available for 255 Mira-like variables which were observed by Hipparcos. Period-luminosity zero-points are evaluated for various subgroups of data. The best solution for oxygen-rich Miras, which uses 180 stars, omi…
Ultraviolet Galaxy Counts from Space Telescope Imaging Spectrograph Observations of the Hubble Deep Fields
Ferguson, Henry C.; Brown, Thomas M.; Gardner, Jonathan P.
We present galaxy counts in the near-ultraviolet (NUV; 2365 Å) and far-ultraviolet (FUV; 1595 Å) obtained from Space Telescope Imaging Spectrograph observations of portions of the Hubble Deep Field-North (HDF-N), the Hubble Deep Field-South (HDF-S), and a parallel field near the HDF-N. All three fields have deep (AB>29) optical imaging, and we …