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Local Interstellar Medium Properties and Deuterium Abundances for the Lines of Sight toward HR 1099, 31 Comae, β Ceti, and β Cassiopeiae
Wood, Brian E.; Linsky, Jeffrey L.; Dempsey, Robert C. +2 more
We analyze Goddard High-Resolution Spectrograph data to infer the properties of local interstellar gas and the deuterium/hydrogen (D/H) ratio for lines of sight toward four nearby late-type stars--HR 1099, 31 Comae, β Ceti, and β Cassiopeiae. The data consist of spectra of the hydrogen and deuterium Lyα lines, and echelle spectra of the Mg II h an…
Peculiar Multimodality on the Horizontal Branch of the Globular Cluster NGC 2808
Rich, R. Michael; Renzini, Alvio; Piotto, Giampaolo +6 more
We present distributions of colors of stars along the horizontal branch (HB) of the globular cluster NGC 2808, from Hubble Space Telescope Wide Field Planetary Camera 2 imaging in B, V, and an ultraviolet filter (F218W). This cluster's HB is already known to be strongly bimodal, with approximately equal-sized HB populations widely separated in the…
The Hubble Space Telescope Extragalactic Distance Scale Key Project. VII. The Discovery of Cepheids in the Leo I Group Galaxy NGC 3351
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +20 more
We report of the discovery and properties of Cepheid variable stars in the barred spiral galaxy NGC 3351 which is a member of the Leo I group of galaxies. NGC 3351 is one of 18 galaxies being observed as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale which aims to determine the Hubble constant to 10% accur…
Hubble Space Telescope Ultraviolet Observations of the Cores of M3 and M13
Ferraro, Francesco R.; Paltrinieri, Barbara; Fusi Pecci, Flavio +3 more
We present preliminary results from Hubble Space Telescope (HST)/WFPC2 observations of the central regions of the of the Galactic globular clusters M13 and M3. The clusters are almost identical in most respects, including chemical composition, but there are dramatic differences in both the horizontal-branch (HB) and blue straggler populations. The…
High Carbon in I Zwicky 18: New Results from Hubble Space Telescope Spectroscopy
Garnett, D. R.; Skillman, E. D.; Dufour, R. J. +1 more
We present new measurements of the gas-phase C/O abundance ratio in both the northwest (NW) and southeast (SE) components of the extremely metal-poor dwarf irregular galaxy I Zw 18, based on ultraviolet spectroscopy of the two H II regions using the Faint Object Spectrograph on the Hubble Space Telescope. We determine values of log C/O = -0.63 +/-…
Lyman-Alpha Absorption and the D/H Ratio in the Local Interstellar Medium
Vidal-Madjar, A.; Audouze, J.; Landsman, W. +5 more
Using the Goddard High Resolution Spectrograph onboard the Hubble Space Telescope, we have observed Lyα absorption against stellar chromospheres along six lines of sight, with additional observations of the Mg II H and K lines along five of the lines of sight and Fe II absorption along four of the lines of sight. We found absorption near the proje…
HST and Merlin Observations of 3C 264--A Laboratory for Jet Physics and Unified Schemes
Baum, Stefi A.; O'Dea, Christopher P.; Sparks, William B. +10 more
We present new HST optical continuum and emission line WFPC2 images and MERLIN radio observations of 3C 264 at ~0.1" resolution. The jet is well resolved in both the optical and radio images. In addition, we report the discovery of an apparent optical ``ring'' at a projected radius of ~300-400 pc. The ring is most likely the manifestation of absor…
A New Measurement of the Electron Density in the Local Interstellar Medium
Wood, Brian E.; Linsky, Jeffrey L.
Using the echelle-A grating of the Goddard High-Resolution Spectrograph, we have observed the C II λλ1335, 1336 emission lines of the nearby (d = 13.3 pc) star system Capella (G8 III + G1 III). Interstellar C II absorption features are detected within both stellar emission lines. The ground-state and excited-state C II column densities derived fro…
Hubble Space Telescope Imaging of z >= 0.4 Quasar Host Galaxies Selected by Quasar Radio and Optical Properties
Foltz, Craig B.; Hooper, Eric J.; Impey, Chris D.
A sample of 16 quasars selected from the Large Bright Quasar Survey in the redshift range 0.4 < z < 0.5 has been imaged in the R band with the Planetary Camera on the WFPC2 instrument of the Hubble Space Telescope. The host galaxy magnitudes are mostly similar to or brighter than L*, and the host luminosity is positively correlated with the …
Multiwavelength Observations of 3C 273 in 1993-1995
McHardy, I.; Ghisellini, G.; McBreen, B. +30 more
We present the results of the multiwavelength campaigns on 3C 273 in 1993-1995. During the observations in late 1993, this quasar showed an increase of its flux for energies >=100 MeV from about 2.1 × 10-7 photons cm-2 s-1 to approximately 5.6 × 10-7 photons cm-2 s-1 during a rad…