A spectroscopic study of the peculiar galaxy UGC 5600     

L. V. Shalyapina  A. V. Moiseev  V. A. Yakovleva 《Astronomy Letters》2002,28(7):443-453

We present our observations of the galaxy UGS 5600 with a long-slit spectrograph (UAGS) and a multipupil field spectrograph (MPFS) attached to the 6-m Special Astrophysical Observatory telescope. Radial-velocity fields of the stellar and gaseous components were constructed for the central region and inner ring of the galaxy. We proved the existence of two nearly orthogonal kinematic subsystems and conclude that UGC 5600 is a galaxy with an inner polar ring. In the circumnuclear region, we detected noncircular stellar motions and suspected the existence of a minibar. The emission lines are shown to originate in H II regions. We estimated the metallicity from the intensity ratio of the [N II]λ6583 and Hα lines to be nearly solar, which rules out the possibility that the polar ring was produced by the accretion of gas from a dwarf companion.  相似文献   

Identification of mercurian volcanism: Resolution effects and implications for MESSENGER     

S. M. MILKOVICH  J. W. HEAD  L. WILSON 《Meteoritics & planetary science》2002,37(9):1209-1222

Abstract— The possibility of volcanism on Mercury has been a topic of discussion since Mariner 10 returned images of half the planet's surface showing widespread plains material. These plains could be volcanic or lobate crater ejecta. An assessment of the mechanics of the ascent and eruption of magma shows that it is possible to have widespread volcanism, no volcanism on the surface whatsoever, or some range in between. It is difficult to distinguish between a lava flow and lobate crater ejecta based on morphology and morphometry. No definite volcanic features have been identified on Mercury. However, known lunar volcanic features cannot be identified in images with similar resolutions and viewing geometries as the Mariner 10 dataset. Examination of high‐resolution, low Sun angle Mariner 10 images reveals several features which are interpreted to be flow fronts; it is unclear if these are volcanic flows or ejecta flows. This analysis implies that a clear assessment of volcanism on Mercury must wait for better data. MESSENGER (MErcury: Surface, Space ENvironment, GEochemistry, Ranging) will take images with viewing geometries and resolutions appropriate for the identification of such features.  相似文献   

The mass ratio of Charon to Pluto from Hubble Space Telescope astrometry with the fine guidance sensors     

C.B Olkin  L.H Wasserman  O.G Franz 《Icarus》2003,164(1):254-259

The mass ratio of Charon to Pluto is a basic parameter describing the binary system and is necessary for determining the individual masses and densities of these two bodies. Previous measurements of the mass ratio have been made, but the solutions differ significantly (Null et al., 1993; Young et al., 1994; Null and Owen, 1996; Foust et al., 1997; Tholen and Buie, 1997). We present the first observations of Pluto and Charon with a well-calibrated astrometric instrument—the fine guidance sensors on the Hubble Space Telescope. We observed the motion of Pluto and Charon about the system barycenter over 4.4 days (69% of an orbital period) and determined the mass ratio to be 0.122±0.008 which implies a density of 1.8 to 2.1 g cm⁻³ for Pluto and 1.6 to 1.8 g cm⁻³ for Charon. The resulting rock-mass fractions for Pluto and Charon are higher than expected for bodies formed in the outer solar nebula, possibly indicating significant postaccretion loss of volatiles.  相似文献   

On the accretion geometry of Cyg X-1 in the low/hard state     

F. Eugenio Barrio  Chris Done  Sergei Nayakshin 《Monthly notices of the Royal Astronomical Society》2003,342(2):557-563

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The emission distribution in RR Pictoris     

L. Schmidtobreick  C. Tappert  I. Saviane 《Monthly notices of the Royal Astronomical Society》2003,342(1):145-150

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Ghosts of the Milky Way: a search for topology in new quasar catalogues     

S. J. Weatherley  S. J. Warren  S. M. Croom  R. J. Smith  B. J. Boyle  T. Shanks  L. Miller  M. P. Baltovic 《Monthly notices of the Royal Astronomical Society》2003,342(1):L9-L13

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SN 1999E: another piece in the supernova–gamma-ray burst connection puzzle     

L. Rigon  M. Turatto  S. Benetti  A. Pastorello  E. Cappellaro  I. Aretxaga  O. Vega  V. Chavushyan  F. Patat  I. J. Danziger  M. Salvo 《Monthly notices of the Royal Astronomical Society》2003,340(1):191-196

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Double–double radio galaxies: remnants of merged supermassive binary black holes     

F. K. Liu  Xue-Bing Wu  S. L. Cao 《Monthly notices of the Royal Astronomical Society》2003,340(2):411-416

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Digital photographic photometry of NGC 5253 and NGC 2915     

J. L. Sérsic  C. J. Donzelli 《Astrophysics and Space Science》1992,193(1):87-94

The surface digital photometry for NGC 5253 and NGC 2915 is given. The luminosity profiles and colour gradients are discussed and compared. It is concluded that NGC 2915 differs from NGC 5253, both in the extension and intensity of the star burst event because of the kinematical behaviour of the captured gas.CONICET, Buenos Aires, Visiting Astronomer, Cerro Tololo Inter-American Observatory, La Serena, Chile, operated by NSF  相似文献   

On the relationship between the Apollo 16 ancient regolith breccias and feldspathic fragmental breccias,and the composition of the prebasin crust in the Central Highlands of the Moon     

Randy L. Korotev 《Meteoritics & planetary science》1996,31(3):403-412

Abstract Two types of texturally and compositionally similar breccias that consist largely of fragmental debris from meteorite impacts occur at the Apollo 16 lunar site: Feldspathic fragmental breccias (FFBs) and ancient regolith breccias (ARBs). Both types of breccia are composed of a suite of mostly feldspathic components derived from the early crust of the Moon and mafic impact-melt breccias produced during the time of basin formation. The ARBs also contain components, such as agglutinates and glass spherules, indicating that the material of which they are composed occurred at the surface of the Moon as fine-grained regolith prior to lithification of the breccias. These components are absent from the FFBs, suggesting that the FFBs might be the protolith of the ARBs. However, several compositional differences exist between the two types of breccia, making any simple genetic relationship implausible. First, clasts of mafic impact-melt breccia occurring in the FFBs are of a different composition than those in the ARBs. Also the feldspathic “prebasin” components of the FFBs have a lower average Mg/Fe ratio than the corresponding components of the ARBs; the average composition of the plagioclase in the FFBs is more sodic than that of the ARBs; and there are differences in relative abundances of rare earth elements. The two breccia types also have different provenances: the FFBs occur primarily in ejecta from North Ray crater and presumably derive from the Descartes Formation, while the ARBs are restricted to the Cayley plains. Together these observations suggest that although some type of fragmental breccia may have been a precursor to the ARBs, the FFBs of North Ray crater are not a significant component of the ARBs and, by inference, the Cayley plains. The average compositions of the prebasin components of the two types of fragmental breccia are generally similar to the composition of the feldspathic lunar meteorites. With 30–31% Al₂O₃, however, they are slightly richer in plagioclase than the most feldspathic lunar meteorites (～29% Al₂O₃), implying that the crust of the early central nearside of the Moon contained a higher abundance of highly feldspathic anorthosite than typical lunar highlands, as inferred from the lunar meteorites. The ancient regolith breccias, as well as the current surface regolith of the Cayley plains, are more mafic than (1) prebasin regoliths in the Central Highlands and (2) regions of highlands presently distant from nearside basins because they contain a high abundance (～30%) of mafic impact-melt breccias produced during the time of basin formation that is absent from other regoliths.  相似文献