Search Publications
Probing Cosmology with the X-Ray Forest
Canizares, Claude R.; Fang, Taotao
There is a growing consensus that in the present universe most baryons reside in galaxy clusters and groups in the form of highly ionized gas at temperatures of 106-108 K. The H-like and He-like ions of the heavy elements can produce absorption features-the so-called ``X-ray forest''-in the X-ray spectrum of a background quas…
On the Nature of Andromeda IV
Gallagher, J. S.; Wyse, Rosemary F. G.; Ferguson, Annette M. N.
Lying at a projected distance of 40' or 9 kpc from the center of M31, Andromeda IV is an enigmatic object first discovered during van den Bergh's search for dwarf spheroidal companions to M31. Since it is bluer, more compact, and has a higher surface brightness than other known dwarf spheroidals, it has been suggested that And IV is either a relat…
Latitudinal dependence of outflow velocities from O VI Doppler dimming observations during the Whole Sun Month
Kohl, John L.; Noci, Giancarlo; Gibson, Sarah E. +4 more
Empirical determinations of outflow velocities in the solar corona provide a much needed constraint, along with density and temperature determinations, of the acceleration and heating mechanisms in the extended corona. Much progress has been made on density determinations from white light polarized brightness observations but outflow velocities ha…
Comparison of far-ultraviolet emission lines formed in coronal holes and the quiet Sun
Solanki, S. K.; Wilhelm, K.; Brković, A. +5 more
We present an analysis of 26 far-ultraviolet emission lines belonging to 19 atoms and ions observed on both sides of the boundary of polar coronal holes as well as other quiet Sun areas along the limb. The observations were made with the SUMER instrument (Solar Ultraviolet Measurements of Emitted Radiation) onboard the Solar and Heliospheric Obser…
ISO-LWS spectroscopy of Centaurus A: extended star formation
Spinoglio, L.; Lord, S. D.; Stacey, G. J. +9 more
We present the first full FIR spectrum of Centaurus A (NGC 5128) from 43 - 196.7 µm. The data was obtained with the ISO Long Wavelength Spectrometer (LWS). We conclude that the FIR emission in a 70 \arcsec beam centred on the nucleus is dominated by star formation rather than AGN activity. The flux in the far-infrared lines is ~ 1% of the to…
Far Ultraviolet Spectroscopic Explorer Spectroscopy of the O VI Resonance Doublet in Sand 2 (WO)
Sonneborn, G.; Hillier, D. J.; Willis, A. J. +9 more
We present Far Ultraviolet Spectroscopic Explorer spectroscopy of Sand 2, an LMC WO-type Wolf-Rayet star, revealing the O VI resonance P Cygni doublet at 1032-1038 Å. These data are combined with Hubble Space Telescope Faint Object Spectrograph ultraviolet and Mount Stromlo 2.3 m optical spectroscopy and analyzed using a spherical, non-LTE, line-b…
Gasdynamics in the LINER Galaxy NGC 5005: Episodic Fueling of a Nuclear Disk
Sakamoto, Kazushi; Baker, Andrew J.; Scoville, Nick Z.
We report high-resolution CO(1-0) observations in the central 6 kpc (1') of the LINER galaxy NGC 5005 with the Owens Valley Radio Observatory millimeter array. Molecular gas is distributed in three components-a ring at a radius of about 3 kpc, a strong central condensation, and a stream to the northwest of the nucleus but inside the 3 kpc ring. Th…
Solar Cycle Variation in Solar f-Mode Frequencies and Radius
Basu, Sarbani; Antia, H. M.; Pintar, J. +1 more
Using data from the Global Oscillation Network Group (GONG) covering the period from 1995 to 1998, we study the change with solar activity in solar f-mode frequencies. The results are compared with similar changes detected from the Michelson Doppler Imager (MDI) data. We find variations in f-mode frequencies which are correlated with solar activit…
Slowdown of the Solar Wind in the Outer Heliosphere and the Interstellar Neutral Hydrogen Density
Wang, C.; Richardson, J. D.; Gosling, J. T.
Voyager 2 and Ulysses were at nearly the same latitude in the southern heliosphere at the beginning of 1999 and their radial separation was about 55 AU. The effect of pickup ions should be profound at Voyager's position, especially, the deceleration of the solar wind flow. This unique opportunity allows us to investigate the effect of pickup ions …
Distribution of Supergranular Sizes
Singh, Jagdev; Raju, K. P.; Srikanth, R.
A gradient-based method of tessellation was applied to SOHO Dopplergrams and to Ca II K filtergrams in order to study the cellular pattern of the solar surface, in specific the geometric relationship between the tessellation and the chromospheric network/supergranulation. We found that for zero spatial smoothing and low temporal averaging the abov…