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Rocket Observations of Far-Ultraviolet Dust Scattering in NGC 2023
Feldman, Paul D.; Burgh, Eric B.; McCandliss, Stephan R.
The reflection nebula NGC 2023 was observed by a rocket-borne long-slit imaging spectrograph in the 900-1400 Å bandpass on 2000 February 11. A spectrum of the star, as well as that of the nebular scattered light, was recorded. Through the use of a Monte Carlo modeling process, the scattering properties of the dust were derived. The albedo is low, …
Optical and Near-Infrared Structural Properties of Cluster Galaxies at z ~ 0.3
Capaccioli, M.; La Barbera, F.; Merluzzi, P. +2 more
Structural parameters (half-light radius re, mean effective surface brightness <µ>e, and Sersic index n, parameterizing the light profile shape) are derived for a sample of galaxies in the rich cluster AC 118 at z=0.31, so far the largest (N=93) sample of galaxies at intermediate redshift with structural parameter…
Chandra Observations of Galaxy Cluster A2218
Garmire, Gordon P.; Canizares, Claude; Bautz, Mark W. +1 more
We present results from two observations (combined exposure of ~17 ks) of galaxy cluster A2218 using the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory that were taken on 1999 October 19. Using a Raymond-Smith single-temperature plasma model corrected for galactic absorption, we find a mean cluster temperature of kT=6.9+/…
Quiescent Solar Prominences and Magnetic-Energy Storage
Low, B. C.; Fan, Y.; Fong, B.
Analytical solutions are presented to describe the hydromagnetic support of quiescent solar prominences treated as cold plasma sheets in the characteristic normal and inverse configurations. The solar corona is modeled to be axisymmetric outside a unit sphere, with the prominence sheet lying in the equatorial plane extending from the sphere out to…
Molecular Gas in Candidate Double-barred Galaxies. I. The Diverse Morphology and Dynamics of NGC 2273 and NGC 5728
Wilson, Christine D.; Petitpas, Glen R.
Double bars have been proposed as a means of transporting molecular gas past inner Lindblad resonances into the nuclear regions, where it can fuel active or starburst nuclei. Thus far, the existence of double bars has been determined predominantly through analysis of near-infrared images, which can tell us little about the dynamics and inflow rate…
Resonance Line Profile Calculations Based on Hydrodynamical Models of Cataclysmic Variable Winds
Kallman, Timothy R.; Drew, Janet E.; Hartley, Louise E. +1 more
We describe a method of calculating synthetic line profiles using a generalized version of the Sobolev approximation. We apply this method to calculate line profiles predicted by the models of two-dimensional line-driven winds from luminous disks due to Proga, Stone, & Drew. We describe the main properties of the model line profiles and compar…
Measurements of Three-dimensional Coronal Magnetic Fields from Coordinated Extreme-Ultraviolet and Radio Observations of a Solar Active Region Sunspot
Landi, Enrico; Brosius, Jeffrey W.; Gopalswamy, N. +3 more
We observed NOAA Active Region 8108 around 1940 UT on 1997 November 18 with the Very Large Array and with three instruments aboard the NASA/ESA Solar and Heliospheric Observatory satellite, including the Coronal Diagnostic Spectrometer, the EUV Imaging Telescope, and the Michelson Doppler Imager. We used the right-hand and left-hand circularly pol…
Analytic and Numerical Models for the Knots along the HH 111 Jet
Velázquez, P. F.; Raga, A. C.; Noriega-Crespo, A. +2 more
We consider a model for HH 111 as a jet ejected with a sawtooth, time-dependent ejection velocity. Such a variability is suggested by the position-velocity (PV) diagrams obtained from Hubble Space Telescope observations. We calculate both analytic and numerical models describing the flow resulting from such an ejection velocity time variability. A…
Hubble Space Telescope Imaging in the Chandra Deep Field-South. II. WFPC2 Observations of an X-Ray Flux-limited Sample from the 1 Million Second Chandra Catalog
Grogin, Norman A.; Koekemoer, Anton M.; Marconi, A. +10 more
We present Hubble Space Telescope/WFPC2 observations of a well-defined sample of 40 X-ray sources with X-ray fluxes above the detection threshold of the full 1 Ms Chandra Deep Field-South (CDF-S). The sensitivity and spatial resolution of our HST observations are sufficient to detect the optical counterparts of 37 of the X-ray sources, yielding in…
Dusty Acoustic Turbulence in the Nuclear Disks of Two LINER Galaxies NGC 4450 and NGC 4736
Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Eberwein, Kate S.
The structure of dust spirals in the nuclei of the SAab-type LINER galaxies NGC 4450 and NGC 4736 is studied using archival Hubble Space Telescope Planetary Camera images. The spirals are typically only several hundredths of a magnitude fainter than the neighboring disks, so unsharp-mask techniques are used to highlight them. The ambient extinctio…