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541.
D. F. Roscoe 《Journal of Astrophysics and Astronomy》1997,18(4):407-414
One of the largest rotation curve data bases of spiral galaxies currently available is that provided by Persic& Salucci (1995;
hereafter, PS) which has been derived by them from unreduced rotation curve data of 965 southern sky spirals obtained by Mathewson,
Ford& Buchhorn (1992; hereafter, MFB). Of the original sample of 965 galaxies, the observations on 900 were considered by
PS to be good enough for rotation curve studies, and the present analysis concerns itself with these 900 rotation curves.
The analysis is performed within the context of the hypothesis that velocity fields within spiral discs can be described by
generalized power-laws. Rotation curve data was found to impose an extremely strong and detailed correlation between the free
parameters of the power-law model, and this correlation accounts for virtually all the variation in the pivotal diagram. In
the process, the analysis reveals completely unexpected structure which indicates that rotation curves can be partitioned
into well-defined discrete subclasses. 相似文献
542.
The extraordinary brightness of comet Hale-Bopp (C/1995 O1) offered the rare opportunity to investigate its ion tail by observations
over a wide range of wavelengths. For the first time, ion emission lines could be detected in the radio domain, originating
from H3O+, HCO+ and CO+ ions. Observations in the extreme ultraviolet range showed O+ emissions. Optical imaging observations show a spectacular detail of structures in the ion tail. The combined measurements
of the ion spatial distribution and dynamic provide a wealth of information which needs to be understood in terms of models
of the comet-solar wind interaction and ion-neutral molecule reactions in the coma.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
543.
L. L. Kitchatinov 《Astronomy Letters》2002,28(9):626-631
We propose a solution to one of the oldest problems in the solar-dynamo theory: explaining the equatorward drift of magnetic activity in the solar cycle. The well-known suggestion that the dynamo waves propagate along the surfaces of constant angular velocity is shown to be restricted to an isotropic medium. Allowance for the rotation-induced anisotropy in turbulent diffusion leads to an equatorward deviation of the wave phase velocity from the isorotational surface. Estimates for the dynamo waves are illustrated with two-dimensional numerical models in a spherical geometry. The model with anisotropic diffusion also shows an equatorward drift of the toroidal magnetic field when the rotation is radially uniform. 相似文献
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545.
During CO observations of new Southern objects with the 15-m SEST mm telescope (Cerro La Silla, Chile) we have found that the globule connected with the object CLN127-128 rotates with an angular velocity 4.3 · 10-14 s-1, which corresponds to the velocity of extremely fast rotating globules. The object CLN127-128 is a chain of three stars; two of them are connected with bright nebulae, and the third is a suspected Herbig Ae/Be star. All three stars are bright in near IR, which is specific for the existence of circumstellar shells (or disks) around them. The specific angular momentum of the globule confirms that it is in virial equilibrium. Besides the finding of a rotating globule, CO observations suggest the presence of a blue-shifted outflow from CLN127-128 with a velocity of -1.1 km/s (in the system connected with the globule). 相似文献
546.
晚型星系金属丰度与自转速度的关系 总被引:1,自引:0,他引:1
星系物质化学组成的研究不仅对于理解有关星系形成和演化的各种物理过程具有重要意义,而且还可以对星系形成和演化的各种理论模型提供重要的约束。随着观测技术及理论工作水平的不断提高,利用星系的大量观测资料来系统地研究星系化学组成与星系宏观性质之间的关系将成为可能。星系金属丰度与光度之间的强相关性以及晚型星系金属丰度与自转速度的关系即是其中最有意义的内容之一。全面回顾了星系金属丰度与星系宏观观测性质间关系的研究历史,重点评述了晚型星系金属丰度与自转速度关系的最新研究进展,详细讨论了目前对此类关系的物理解释及其对星系形成和演化模型的影响。 相似文献
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550.
During the last two minutes before closest approach of Deep Space 1 to Comet 19P/Borrelly, a long exposure was made with the short-wavelength infrared (SWIR) imaging spectrometer. The observation yielded 46 spectra covering 1.3-2.6 μm; the footprint of each spectrum was ∼160 m × width of the nucleus. Borrelly's highly variegated and extremely dark 8-km-long nucleus exhibits a strong red slope in its short-wavelength infrared reflection spectrum. This slope is equivalent to J-K and H-K colors of ∼0.82 and ∼0.43, respectively. Between 2.3-2.6 μm thermal emission is clearly detectable in most of the spectra. These data show the nucleus surface to be hot and dry; no trace of H2O ice was detected. The surface temperature ranged continuously across the nucleus from ?300 K near the terminator to a maximum of ∼340 K, the expected sub-solar equilibrium temperature for a slowly rotating body. A single absorption band at ∼2.39 μm is quite evident in all of the spectra and resembles features seen in nitrogen-bearing organic molecules that are reasonable candidates for compositional components of cometary nuclei. However as of yet the source of this band is unknown. 相似文献