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|ROSAT HRI observations of six early-type galaxies|
High-resolution ROSAT HRI soft X-ray observations of four E/S0 galaxieswere conducted by us. The data show no signs of Seyfert activity in theX-ray regime. The central emission peaks of the four galaxies, NGC533,NGC2832, NGC4104 and NGC6329, are associated with their cooling flows.The half intensity radii of the cooling flows range from 0.8 to 3.5 kpc.We find a trend (based up to now on only five objects) of the radiopower of the cores in E/S0 galaxies to increase with the size and theaccretion rates of their cooling flows. In one galaxy, NGC4921, nocentrally peaked extended gaseous envelope was found, which is mostlikely due to the fact that it is not an E/S0 galaxy, but an early-typespiral. NGC2885, the sixth galaxy in our initial sample, shows signs ofX-ray emission from an AGN. It has also been classified as a Sy-1 AGN byBade et al. (1995). However, optical imaging suggests that this galaxyis probably not an E or S0 type system either, but rather an early-typespiral galaxy. Thus, in the context of accretion rate vs. galaxy typemodels of low-luminosity AGNs, the presence of an X-ray luminous Sy-1nucleus in NGC2885 is no surprise.
|A method for reconstructing the full vector velocity field in the gaseous disks of spiral galaxies|
A method is proposed for reconstructing the full vector velocity field(i.e., the three velocity components) in the gaseous disks of spiralgalaxies from observed radial velocities. The method is based on Fourieranalysis of the observed velocity field and interpretation of theresulting Fourier harmonics in the framework of a model accounting formotion in the spiral arms. The model is based on the concept of galacticspirals as density waves. The proposed method can be used to (1) findnoncircular velocities associated with spiral-vortex structure; (2) findfundamental parameters for this structure, such as the angularrotational velocity, the corotation radius, and the location of giantanticyclones; (3) refine the rotation curves of galaxies by taking intoaccount noncircular velocities in spiral density waves, which leads to amore precise determination of the mass distribution in the galaxies; and(4) refine parameters determining the galactic plane: inclination angle,location of the center of rotation, and the position angle of the majordynamical axis of the galaxy. Knowledge of the velocity field in spiralgalaxies makes it possible to better understand galactic structures andmechanisms for their formation.
|A list of some corrections to Zwicky's Catalogue of Galaxies and Clusters of Galaxies|
|The Maxwellian alternative to the dark matter problem in galaxies|
The observed superrotation of the material at the outer edge of galaxiesis considered theoretically. Instead of explaining this motion in termsof a dark-matter halo, a Maxwellian-type interaction between masses isproposed. In this scheme, the luminous matter in the central galaxy andits motion provide the sources and vortices of a generalizedgravitational field, and a gravoinductional force generated by masscurrents leads to a new type of gravitational coupling between masses.It is shown analytically that this mechanism should have a greatereffect than Newtonian gravity at large distances from the rotatingcentral mass. Several specific problems are explored, and possibleobservational tests of the theory are discussed.
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