THE NATURE OF ELONGATED ELLIPTICALS

We have analyzed the isophotal shapes of a sample of 63 elongated elli ptical galaxies, previously classified E4, 5, 6 or 7. We sorted them a ccording to their isophotal class, defined by the type of deviations f rom perfectly elliptical isophotal contours. These deviations are expe cted to appear clearly, because of the very favorable orientation of t hese galaxies. We find the following results, after exclusion of 6 non -elliptical galaxies: A large percentage (56%) of elongated E's are di sky objects with pointed isophotes, while only 35% have either boxy or irregular isophotes, in equal proportions, and the remaining 6 galaxi es (10%) are difficult to classify. Furthermore, 38% of disky E's also show slightly boxy spheroids. In almost all the galaxies of the sampl e, there is an angular range where the deviations are of the disk-type . The four galaxies not showing this effect are among the roundest one s of the sample, which suggests that projection effects hide detailed structures of this kind in many ellipticals. The correlations already reported in the literature between isophotal class and radio, X-ray em ission and kinematical behavior are confirmed. In particular, there is a clear-cut correlation between velocity anisotropy and isophotal sha pe. The most elongated Hubble types tend to be disky E's. Boxy/irregul ar E's rarely exceed ellipticities of 0.45 while the maximum elliptici ty of half of the disky E's exceeds this value. These results confirm the dichotomy of E's, which fall roughly into two classes, disky and b oxy/irregular ellipticals. They also show a physical continuity betwee n disky E's and SO's and suggest that the Hubble types are strongly co rrelated with disk-to-bulge ratios throughout the Hubble sequence, eve n at its early-type end (round E's), for which the disk is hidden by o rientation effects. Galaxies escaping the correlations are the boxy/ir regular E's, resulting probably from strong merging processes.