ar X iv : a st ro - p h / 98 11 41 6 v 1 2 6 N ov 1 99 8 Elliptical Galaxies : Detailed Structure , Scaling Relations and Formation

The last decade of research on elliptical galaxies has produced a wealth of new information concerning both their detailed structure and their global scaling relations. We review the old and new results about isophote shapes and subcomponents (Sect. 1.), scaling relations of global parameters and redshift evolution (Sect. 2.), and the ages, metallicities (Sect. 3.) and abundance ratios (Sect. 4.). Finally, we confront the observations with hierarchical formation scenarios of elliptical galaxies (Sect. 5.). The picture emerging from this variety of observational evidence is broadly consistent with the merging scenario of hierarchical structure formation models, but the stellar population properties of ellipticals pose some challanges. The formation of ellipticals must have always involved some dissipation. The gas fraction at the last major merger event presumably has strong influence on their present day properties. Most elliptical galaxies are old systems, but disky ellipticals might be younger than boxy objects and have more extended star formation histories. The small scatter and the redshift variations of the scaling relation are compatible with passive evolution. The high Mg/Fe overabundances of luminous (boxy) ellipticas point to a rapid star formation episode, while low-luminosity objects have values of Mg/Fe nearly solar, allowing for an extended star formation history. 1. Isophote shapes, sub-components and kinematics Isophote shapes have proven to be an easily measurable indicator for the internal kinematics and core structure of ellipticals as well as for their radio and X-ray properties (e.g., Bender 1988a, 1997, Bender et al. 1989, Faber et al. 1997, Beuing et al. 1998). Boxy ellipticals are characterized by anisotropy and shallow cores, and by stronger than average radio and X-ray emission. Disky ellipticals contain faint stellar disks, are rotationally flattened, have power-law inner density profiles and show little or no radio and X-ray emission. The disk-to-bulge ratios of disky ellipticals can be as high as 0.3 and overlap those of S0-galaxies (Rix & White 1990, Scorza & Bender 1995). Generally, the spheroids are rotationally supported and the angular momenta of disks and bulges are parallel to each other indicating that the disks were not randomly accreted at late times (Bender et al. 1993, Scorza & Bender 1995). The high density power-law centers of disky Es (Faber et al. 1997) and the fact these