APPARENT AND TRUE FLATTENING DISTRIBUTION OF ELLIPTIC GALAXIES

CCD photometry of 204 objects from the literature has been used to produce a new distribution of the flattening of elliptical galaxies. All flattenings are referred to the effective isophote. Our distribution is remarkably different from previous ones essentially because of the deficiency of low-ellipticity objects. The rectification algorithm by Lucy has been used to deproject the distribution on the basis of hypotheses that the objects are oblate, and prolate, but neither of these hypotheses can explain the lack of round objects which are observed. This gives the first statistical evidence that ellipticals cannot constitute a population of purely biaxial objects. Among other possibilities, the presence of a small degree of triaxiality in a single galaxy population, and the existence of two different populations, are discussed.