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Deuterium and the Local Interstellar Medium Properties for the Procyon and Capella Lines of Sight
Ayres, Thomas R.; Savage, Blair D.; Brown, Alexander +3 more
We present Goddard High-Resolution Spectrograph observations of the interstellar H I and D I Lyα lines and the Mg II and Fe II resonance lines formed along the lines of sight toward the nearby stars Procyon (3.5 pc, l = 214°, b = 13°) and Capella (12.5 pc, l = 163°, b = 5°). New observations of Capella were obtained at orbital phase 0.80, when the…
The Intermediate Stellar Mass Population in R136 Determined from Hubble Space Telescope Planetary Camera 2 Images
Holtzman, Jon A.; Lynds, Roger; Light, Robert M. +3 more
We have analyzed Hubble Space Telescope (HST) images of the compact, luminous star cluster R136 in the LMC that were taken with the refurbished HST and new Wide Field/Planetary Camera. These images allow us to examine the stellar population in a region of unusually intense star formation at a scale of 0.01 pc. We have detected stars to 23.5 in F55…
The Southern High-Speed Stream: Results from the SWICS Instrument on Ulysses
Livi, S.; Balsiger, H.; Geiss, J. +8 more
The high-speed solar wind streaming from the southern coronal hole was remarkably uniform and steady and was confined by a sharp boundary that extended to the corona and chromosphere. Charge state measurements indicate that the electron temperature in this coronal hole reached a maximum of about 1.5 million kelvin within 3 solar radii of the sun. …
The D/H and ^18^O/^16^O ratios in water from comet P/Halley.
Eberhardt, P.; Krankowsky, D.; Hodges, R. R. +1 more
From a detailed evaluation of the ion currents measured by the Neutral Mass Spectrometer (NMS) on the Giotto spaceprobe in the 17.5amu/e to 21.5amu/e mass range inside the contact surface of P/Halley we derive the cometary ion densities for masses 18amu/e to 21amu/e. From these we calculate the deuterium and ^18^O abundances in the H_3_O^+^ ion to…
The morphological identification of the rapidly evolving population of faint galaxies
Ellis, Richard; Glazebrook, Karl; Griffiths, Richard +1 more
The excess numbers of blue galaxies at faint magnitudes are a long-standing cosmological puzzle. We present new number-magnitude counts as a function of galactic morphology from the first deep fields of the Cycle 4 Hubble Space Telescope Medium Deep Survey project. From a sample of 301 galaxies we define counts for elliptical, spiral and irregular…
Spectral Classification of Galaxies: an Orthogonal Approach
Calzetti, D.; Kinney, A. L.; Connolly, A. J. +2 more
Classification of galaxy spectral energy distributions in terms of orthogonal basis functions provides an objective means of estimating the number of significant spectral components that comprise a particular galaxy type. We apply the Karhunen-Loeve transform to derive a spectral eigensystem from a sample of ten galaxy spectral energy distribution…
Radiative Levitation in Hot White Dwarfs: Equilibrium Theory
Chayer, P.; Fontaine, G.; Wesemael, F.
We present the results of detailed calculations of radiative levitation in hot white dwarfs using the extensive and homogeneous atomic data given in TOPBASE. Radiative accelerations and equilibrium abundances have been computed for C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, and Fe on grids of pure hydrogen and pure helium stellar envelope models. The…
The Evolution of C/O in Dwarf Galaxies from Hubble Space Telescope FOS Observations
Terlevich, E.; Terlevich, R.; Garnett, D. R. +5 more
We present UV observations of seven H II regions in low-luminosity dwarf irregular galaxies and the Magellanic Clouds obtained with the Faint Object Spectrograph on the Hubble Space Telescope (HST) in order to measure the C/O abundance ratio in the interstellar medium (ISM) of those galaxies. We measure both O III] 1666 A and C III] 1909 A in our …
A new model for the infrared emission of quasars
Rowan-Robinson, Michael
The optical-UV continua of 75 PG quasars are modelled to test two extreme hypotheses: (a) the range of continuum shapes observed is the result of different amounts of reddening of a single underlying continuum, and (b) the range of continuum slopes is entirely intrinsic, due to accretion discs being viewed at different inclinations. Although (a) i…
Energetic Particle Experiment ERNE
Valtonen, E.; Peltonen, P.; Eronen, T. +12 more
The Energetic and Relativistic Nuclei and Electron (ERNE) experiment will investigate the solar atmosphere and the heliosphere by detecting particles produced in various kinds of energy release processes. ERNE is at the upper end in energy among the SOHO particle instruments. The instrument will measure the energy spectra of elements in the range …