A near-infrared photometric plane for elliptical galaxies and bulges of spiral galaxies

We report the existence of a single plane in the space of global photometri c parameters describing elliptical galaxies and the bulges of early-type sp iral galaxies. The three parameters that define the plane are obtained by f itting the Sersic form to the brightness distribution obtained from near-in frared K-band images. We find, from the range covered by their shape parame ters, that the elliptical galaxies form a more homogeneous population than the bulges. Known correlations like the Kormendy relation are projections o f the photometric plane. The existence of the plane has interesting implica tions for bulge formation models.