Astronomical observations and synthesis of ellipsoidal triaxial structures. I. Geometrical considerations.

Simonneau, E.; Varela, A. M.; Muñoz-Tuñon, C.
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Nuovo Cimento B, Vol. 113B, No. 7, p. 927 - 944

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Isophotal analyses developed in recent years (CCD images and numerical mapping techniques) have revealed that triaxial structures are frequently present in bulges of spirals and in elliptical galaxies. In the first case, these non-axisymmetric oval structures have been proposed as the corresponding sources of the energy necessary to maintain the existence of spiral waves and as a mechanism for re-supplying gas in the inner zones of the galaxy to produce regions of star formation. The photometric diagnostic of these triaxial distributions either from a misalignment between the axes of the ellipse projected by the disc and that of the bulge or from the differential twisting of the elliptical bulge isophotes, required different astronomical techniques. The authors present a complete geometric analysis of both, the direct problem: synthesis of these isophotal contours from a bulge ellipsoidal structure, and the inverse one: the diagnostic of the bulge structure from the measured isophotal parameters.