Stellar Body Research Articles

A Spiral-Like Disk of Ionized Gas in IC 1459: Signature of a Merging Collision?

AbstractWe report the discovery of a large (15 kpc diameter) Hα+[NII] emission-line disk in the elliptical galaxy IC 1459, showing weak spiral structure. The line flux peaks strongly at the nucleus and is more concentrated than the stellar continuum. The major axis of the disk of ionized gas coincides with that of the stellar body of the galaxy. The mass of the ionized gas is estimated to be ~ 1 105 M⊙, less than 1% of the total mass of gas present in IC 1459. The total gas mass of 4 107 M⊙ has been estimated from the dust mass derived from a broad-band colour index image and the IRAS data. We speculate that the presence of dust and gas in IC 1459 is a signature of a merger event.

NGC 5266 - an elliptical galaxy with a dust ring

view Abstract Citations (40) References (58) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS NGC 5266: an Elliptical Galaxy with a Dust Ring Varnas, S. R. ; Bertola, F. ; Galletta, G. ; Freeman, K. C. ; Carter, D. Abstract Results of an inquiry into the nature of the southern galaxy NGC 5266 are presented. New surface photometry indicates that it is an E4 class elliptical with a narrow and slightly warped dust ring wrapping its stellar body in the plane containing its short axis. The extensive spectroscopic observations reveal a very fast cylindrical rotation of the stellar component (Vmax = 212±7 km s-1) around the short axis and smaller rotation (Vmax = 43±16 km s-1) around the long axis. The gas associated with dust rotates around the major axis of the galaxy with a velocity of 260±10 km s-1. It is shown that the true shape of the stellar component in this galaxy is probably triaxial (nearly oblate). Results from dynamical modeling of the dissipative evolution of gas disks embedded in triaxial potentials are also reported. Publication: The Astrophysical Journal Pub Date: February 1987 DOI: 10.1086/164949 Bibcode: 1987ApJ...313...69V Keywords: Astronomical Photometry; Cosmic Dust; Elliptical Galaxies; Galactic Structure; Interstellar Matter; Astronomical Models; Galactic Rotation; Interstellar Gas; Stellar Rotation; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5266; GALAXIES: INTERNAL MOTIONS; GALAXIES: PHOTOMETRY; GALAXIES: STRUCTURE; INTERSTELLAR: MATTER full text sources ADS | data products SIMBAD (4) NED (1)

Properties of Elliptical Galaxies with Dust Lanes

NGC 5128 (Cen A) has been known for many years as a peculiar elliptical, but only recently has it been recognized as the prototype of a new class of object (Bertola and Galletta 1978). This class of galaxy is characterized by an elliptical–like stellar body crossed along the minor axis by a dust lane, and was comprised initially of five objects. The class was extended in a remarkable way by Hawarden et al. (1981), who drew attention also to the existence of ellipticals with the dust lane along the major, and along intermediate axes. Ninety objects are now listed as dust lane ellipticals in the compilation by Ebneter and Balick (1985) and its updated version (Ebneter 1986).

The ultrastructure of Oscillatoria spongeliae, the blue-green algal endosymbiont of the sponge Dysidea herbacea

A number of collections of the tropical sponge Dysidea herbacea (Dictyoceratida, Dysideidae) have been made on the Great Barrier Reef, Australia and the ultrastructure of the filamentous blue-green algal endosymbiont Oscillatoria spongeliae studied in detail. Oscillatoria spongeliae occurs in the mesohyl ofthe ectosome in close association with sponge archaeocytes. Digestion of the algae occurs only rarely, but algae in various stages of digestion have been observed within archaeocytes. The sheathless filaments of O. spongeliae are from four to twenty cells long. Some of the cells of the filament are specialized as necridia, and breakage of filaments along necridial cell walls has been observed. The thylakoids are usually arranged more or less at right angles to the longitudinal cell wall and are evenly spaced around the cell. The algal cells have a typical blue-green algal cell wall and contain various inclusion bodies characteristic of these algae, suggesting that their metabolism must be similar to that of free-living blue-green algae. However, O. spongeliae has a distinctive spherical to spheroidal body with a dark central region and numerous radiating rods which is commonly found in the cytoplasm. We have called this a ‘stellar body’.On the basis of these ultrastructural observations the taxonomic status of this alga is discussed.

Gravitational Self-Lens Effect

The optical image of a luminous mass under the influence of its own gravitational field near the Schwarzschild radius, as in the case of a dense neutron star, is studied. It is found that two important deviations from the classical nonrelativistic behavior occur. First, the stellar body appears to be enlarged by a gravitational self-lens effect. In the limiting case for the star approaching the Schwarzschild radius, the disk appears to be larger by a factor approx equal 2.59. Second, the observed light intensity of the stellar disk appears to be nonunifonn. In the case of a body near the Schwarschild radius the intensity first drops towards the limb of the stellar disk and then sharply rises, forming a system of rings with high-peak intensity near the limb. (auth)

Heating of astrophysical plasma due to rotation

It is shown that low-frequency transverse MHD waves may undergo damping inside a rotating stellar body. It is suggested that rotation may affect the heating of the stellar interior.

Neutrino Theory of Stellar Collapse

At the very high temperatures and densities which must exist in the interior of contracting stars during the later stages of their evolution, one must expect a special type of nuclear processes accompanied by the emission of a large number of neutrinos. These neutrinos penetrating almost without difficulty the body of the star, must carry away very large amounts of energy and prevent the central temperature from rising above a certain limit. This must cause a rapid contraction of the stellar body ultimately resulting in a catastrophic collapse. It is shown that energy losses through the neutrinos produced in reactions between free electrons and oxygen nuclei can cause a complete collapse of the star within the time period of half an hour. Although the main energy losses in such collapses are due to neutrino emission which escapes direct observation. the heating of the body of a collapsing star must necessarily lead to the rapid expansion of the outer layers and the tremendous increase of luminosity. It is suggested that stellar collapses of this kind are responsible for the phenomena of novae and supernovae, the difference between the two being probably due to the difference of their masses.

STELLAR OBJECTS SEEN DURING THE ECLIPSE OF 1869

STELLAR OBJECTS SEEN DURING THE ECLIPSE OF 1869