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Scattered Nuclear Continuum and Broad Hα in Cygnus A
Fosbury, R. A. E.; Miller, J. S.; Ogle, P. M. +3 more
We have discovered scattered broad Balmer emission lines in the spectrum of Cygnus A, using the Keck II Telescope. Broad Hα appears in polarized flux from components on either side of the nucleus and, to a lesser extent, in the nucleus. The full-width at half-maximum of broad Hα is 26,000 km s-1, comparable to the widest emission lines …
Electron Densities in the Solar Polar Coronal Holes from Density-Sensitive Line Ratios of Si VIII and S X
Wilhelm, K.; Schühle, U.; Lemaire, P. +5 more
We derive electron densities as a function of height in the north and south polar coronal holes from a forbidden spectral line ratio of Si VIII. Si VIII is produced at about 8 × 105 K in ionization equilibrium. We also derive densities from a similar line ratio of S X (1.3 × 106 K). The spectra were obtained with the Solar Ul…
Interstellar Abundances in the Magellanic Clouds. I. GHRS Observations of the Small Magellanic Cloud Star Sk 108
York, D. G.; Blades, J. C.; Welty, D. E. +2 more
We present HST GHRS echelle-B and G160M spectra of the Wolf-Rayet binary Sk 108, located in the northeastern part of the main ``bar'' of the Small Magellanic Cloud. The spectra show interstellar absorption from C I, O I, Si II, Si II*, S II, P II, Cr II, Mn II, Fe II, Ni II, and Zn II. We find at least 25 interstellar components, which may be grou…
Models for Dense Molecular Cloud Cores
Neufeld, David A.; Doty, Steven D.
We present a detailed theoretical model for the thermal balance, chemistry, and radiative transfer within quiescent dense molecular cloud cores that contain a central protostar. In the interior of such cores, we expect the dust and gas temperatures to be well coupled, while in the outer regions CO rotational emissions dominate the gas cooling and …
Determination of the Sun's Seismic Radius from the SOHO Michelson Doppler Imager
Kosovichev, A. G.; Schou, J.; Dziembowski, W. A. +1 more
Dopplergrams from the Michelson Doppler Imager (MDI) instrument on board the SOHO spacecraft have been used to accurately measure frequencies of the Sun's fundamental (f) mode in the medium angular degree range, l = 88--250. The comparison of these frequencies with the corresponding frequencies of the standard solar models suggests that the appare…
Discovery of Far-Infrared Pure Rotational Transitions of CH+ in NGC 7027
Barlow, M. J.; Cernicharo, J.; González-Alfonso, E. +4 more
We report the discovery of the rotational spectrum of CH+ in the Infrared Space Observatory Long Wavelength Spectrometer (LWS) spectrum of the planetary nebula NGC 7027. The identification relies on a 1996 reanalysis of the LWS spectrum by Liu et al. and on new LWS data. The strong line at 179.62 µm (coinciding with the 212
The Asymmetric Radio Remnant of SN 1987A
Gaensler, B. M.; Manchester, R. N.; Staveley-Smith, L. +3 more
We present seven years of radio observations of SN 1987A made with the Australia Telescope Compact Array. At 1.4, 2.4, 4.8, and 8.6 GHz, the flux density of the radio remnant has increased monotonically since emission was redetected 1200 days after the explosion. On day 3200, the remnant was expanding at 2800 +/- 400 km s-1, which we in…
Nearby Young Dwarf Galaxies: Primordial Gas and Lyα Emission
Thuan, Trinh X.; Izotov, Yuri I.
We present Hubble Space Telescope UV spectrophotometry of three extremely metal-deficient blue compact dwarf (BCD) galaxies, SBS 0335-052 (Z ~ Z⊙/40), Tol 65 (Z ~ Z⊙/24), and T1214-277 (Z ~ Z⊙/23). Broad damped Lyα absorption is seen in the first two BCDs. For SBS 0335-052, the H I column density derived by fitting…
The Nuclear Stellar Core, the Hot Dust Source, and the Location of the Nucleus of NGC 1068
Genzel, R.; Maiolino, R.; Quirrenbach, A. +2 more
We present new near-infrared speckle and adaptive optics imaging and integral field spectroscopy of the nuclear region of NGC 1068. Ninety-four percent of the K-band light in the central 1" originates from a <=30 milliarcsecond diameter source whose position we determine to coincide within +/-0.15" with the apex of the cone structure seen in th…
Turbulent Velocities and Ion Temperatures in the Solar Corona Obtained from SUMER Line Widths
Wilhelm, K.; Curdt, W.; Schühle, U. +3 more
Turbulent plasma velocities and ion temperatures were determined from the line widths recorded by the Solar Ultraviolet Measurements of Emitted Radiation instrument on the Solar and Heliospheric Observatory spacecraft. From the widths of the lines of five light elements (Ne, Na, Mg, Si, and S) and a heavy element (Fe), it was possible to determine…