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Physical Conditions in the Inner Narrow-Line Region of the Seyfert 2 Galaxy NGC 1068
Crenshaw, D. Michael; Kraemer, Steven B.; Ruiz, José R.
The physical conditions in the inner narrow-line region (NLR) of the Seyfert 2 galaxy NGC 1068 are examined using ultraviolet and optical spectra and photoionization models. The spectra are Hubble Space Telescope archive data obtained with the Faint Object Spectrograph (FOS). We selected spectra of four regions, taken through the 0.3" FOS aperture…
``Baade's Red Sheet'' Resolved into Stars with Hubble Space Telescope in the Blue Compact Dwarf Galaxy VII Zw 403
Hopp, Ulrich; Schulte-Ladbeck, Regina E.; Crone, Mary M.
Hubble Space Telescope Wide Field Planetary Camera 2 observations of the nearby blue compact dwarf galaxy VII Zw 403 (=UGC 6456) resolve single stars down to MI~-2.5, deep enough to identify red giants. This population has a more uniform spatial distribution than the young main-sequence stars and supergiants, forming the structure known…
Hubble Space Telescope Wide Field Planetary Camera 2 Observations of HH 1-2
Hester, J. Jeff; Stapelfeldt, Karl R.; Scowen, Paul A.
We present Hubble Space Telescope Wide Field Planetary Camera 2 images of the bipolar Herbig-Haro complex HH 1-2 in three emission lines (Hα, [S ii], and [O iii]) and one continuum band (F702W). In addition to showing the complex morphology of these objects, the WFPC2 data allow us to resolve the cooling and recombination regions behind radiative …
A Cepheid distance to the Fornax cluster and the local expansion rate of the Universe
Illingworth, Garth D.; Madore, Barry F.; Freedman, Wendy L. +13 more
Both galaxy distances and velocities are required for the determination of the expansion rate of the Universe, as described by the Hubble constant H0. The radial velocities of galaxies arise not just from this expansion but also from random components and large-scale flows. To reach out to distances dominated by the overall cosmic expan…
Measuring Plasma Parameters With Thermal Noise Spectroscopy
Moncuquet, Michel; Issautier, Karine; Meyer-Vernet, Nicole +4 more
This paper describes the basic principles, the unique features and the limitations of thermal noise spectroscopy as a tool for in situ diagnostics in space plasmas. This technique is based on the analysis of the electrostatic field spectrum produced by the quasi-thermal fluctuations of the electrons and ions, which can be measured with a sensitive…
The Opacity of Nearby Galaxies from Colors and Counts of Background Galaxies. I. The Synthetic Field Method and Its Application to NGC 4536 and NGC 3664
Ferguson, Henry C.; Calzetti, Daniela; Panagia, Nino +3 more
We describe a new direct method for determining the opacity of foreground galaxies that does not require any a priori assumptions about the spatial distribution or the reddening law of the obscuring material. The method is to measure the colors and counts of background galaxies that can be identified through the foreground system. The method is ca…
Mass determination of astrometric binaries with Hipparcos. III. New results for 28 systems
Mignard, F.; Martin, C.; McAlister, H. A. +1 more
This paper is the third of a series devoted to the determination of stellar masses from Hipparcos data. This is a continuation of Martin et al. (1997), who introduced the theory and assessed the performance of the method from simulated data, and of a second paper with the first results for 46 systems, ( te[Martin & Mignard 1998]{Mar98}). The o…
On Chromospheric Heating Mechanisms of ``Basal Flux'' Stars
Judge, P. G.; Carpenter, K. G.
Several pieces of evidence have been pieced together over recent years to support the notion that the chromospheric emission measured from stars with convection zones results in part from the upward propagation and dissipation of acoustic waves. One argument, based on a statistical analysis of available UV data of such stars across the H-R diagram…
Alfven wave transmission and particle acceleration in parallel shock waves
Vainio, R.; Schlickeiser, R.
We study Alfven wave transmission through parallel shocks. First, the paper corrects for mistakes made in a previous study by Campeanu & Schlickeiser on the same subject. It is shown, contrary to CS, that first-order Fermi acceleration by multiple shock crossings is generally more effective than stochastic acceleration in the downstream region…
The interstellar extinction in the solar neighbourhood. I. Statistical approach
Egret, D.; Vergely, J. -L.; Koeppen, J. +1 more
Assuming some specific distribution of the interstellar clouds, we interpret the projected stellar extinction in terms of mean extinction by cloud as well as cloud density on the line of sight. Individual stellar extinctions are derived from Stroemgren photometry and from accurate distances based on Hipparcos parallaxes. Extinction profiles as a f…