Two classes of elliptical galaxies are now recognised (Kormendy & Bender 1996). Luminous ellipticals rotate slowly (Davies et al. 1983and tend to have boxy isophotes. Ellipticals fainter than L∗ exhibit an increasing tendency to be rotationally supported and to possess a stellar disk component. This dichotomy led Bender, Burstein & Faber (1992) to suggest that the physical variable that controls the ultimate nature of a forming galaxy is the degree of gaseous dissipation that occurs in the final merger it experiences. Low luminosity systems experience more dissipative mergers which generate high rotation, disky end products. As bigger galaxies are formed, the mergers become increasingly stellar, producing the classical slow rotating ellipticals. They termed this the gas/stellar continuum. This global dichotomy is also reflected in the bimodality of core morphologies of the heterogeneous sample of local ellipticals observed with HST. The low luminosity disky galaxies have ‘hard’ cores with a steep slope in the luminosity profile at small radii, whereas the luminous galaxies have ‘soft’ cores with flat profiles at small radii (e.g. Faber et al. 1997).
Steep-slope field-effect transistors with AlGaN/GaN HEMT and oxide-based threshold switching device