摘要:

AbstractHigh‐resolution (∼1′0…2′4) IRAS maps, optical broad‐band, and narrow‐band images as well as H 1 λ 21 cm data have been used in order to analyse the environment of two large‐scale distortions (LMC 4 and DEM 268) in the disk of the Large Magellanic Cloud. This study has revealed cone‐like structures connected to DEM 268 and LMC 4 indicating high‐velocity cloud impacts as the most probable source of the formation of these two distortions. In both cases, the tip of the cone, which is a place of increased star formation, has a shape which is typical of supersonic motion of gaseous matter through a compressible medium. Expansion velocities of the cone‐like structures of about 12 km·s−1can be derived from the H 1 λ 21 cm data. From these velocities, ages of the distortions of about 40 Myr (LMC 4) and 36 Myr (DEM 268) are estimated. The energy input for the formation of the distortions might have been provided by high velocity clouds with masses of the order of 105M⊙(assuming an initial velocity of 100 km·s−1r

ISSN:0004-6337    

DOI:10.1002/asna.2113170602

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2113170603

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe seventh part of the catalogue of Shakhbazian groups contains the positions and references of all the galaxies of the following 48 groups (north of δ>+2°30′): Shkh 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 142, 149, 150, 153, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166. For the estimation of the coordinates the Digitized Sky Survey was u

ISSN:0004-6337    

DOI:10.1002/asna.2113170604

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractStarting from the equations of hydrodynamics, which include both collisional and collisionless ideal fluids, the special case of pseudo‐arotropes with anisotropic pressure distribution along tangential or vertical direction (in respect to a “vertical” rotation axis) is considered. We find that vertical motions are equivalent to an imaginary rotation, and call “pseudo‐otation” the combination of rotation and real or imaginary peculiar circular motions. By use of a necessary condition for equilibrium, i.e. the coincidence of the boundary with an isopotential (gravitational + rotational centrifugal + real peculiar or imaginary peculiar centrifugal) surface, a new method of finding bifurcation points from axisymmetric to triaxial pseudo‐arotropic sequences – discussed in an earlier paper – is dealt with for the systems under discussion. A simple application to the special case where the isopycnic surfaces are spheroidal discloses that, on one hand, steadily pseudo‐otating, heterogeneous spheroids, cannot be equilibrium configurations and, on the other hand, the same results obtained by use of the virial technique hold when the current method can work. Then the coincidence of the boundary with an isopotential surface and the validity of the virial equations of the second order make two independent (necessary) conditions for equilibrium and both must be satisfied. Under the further assumptions of steady rotation and homeoidally or focaloidally striated distribution of matter, the configurations for which a bifurcation point must necessarily occurr, are determined. In the former alternative a connection is also established, between local (on the boundary) and global anisotropy of pressure distribution; in particular, it is found that local isotropy (on the boundary) involves global isotropy and vice versa. In both cases, the right amount of of anisotropy turns out to yield violation of a treshold for stability, ϵrot= −Erot/Epot⩽ 0.14, conjectured by Ostriker and Peebles (1973). This result gives additional support to a conclusion established in an earlier paper: it seems more germane to speak about Ostriker‐eebles conjecture for stability in connection with visible bodies of galaxies, instead of Ostriker‐eebles criterion for stability in connection

ISSN:0004-6337    

DOI:10.1002/asna.2113170605

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWe found 36 emission lines in the spectrum of the planetary nebula NGC 2438, and we determined its exc. class to be about 6–7. The nebular RVhel= 60.3 ± 3.6 km/s (5 spectra) is in agreement with RVhel= 60.8 ± 4.0 km/s of 4 cluster stars (10 spectra). We conclude that contrary to earlier statements the nebula is probably associated with the clus

ISSN:0004-6337    

DOI:10.1002/asna.2113170606

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe first successful radio astronomical results of measurements of the magnetic field of solar prominences are presented. The accuracy of polarization and magnetic field observations is 3 · · 10−4and 2 G, respectively. The observations were made by the 22‐meter radio telescope of the Crimean Astrophysical Observatory at wavelengths of 8 and 13.5 mm. It has been found that the value of the magnetic fields coincides with the optical one (from 7 to 30 G), but the image of radio polarization differs from the inte

ISSN:0004-6337    

DOI:10.1002/asna.2113170607

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2113170608

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2113170609

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2113170601

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY