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 photometric parameters describing elliptical galaxies and the bulges of early-type spiral galaxies. The three parameters that define the plane are obtained by fitting the Sersic form to the brightness distribution obtained from near-infrared K-band images. We find, from the range covered by their shape parameters, that the elliptical galaxies form a more homogeneous population than the bulges. Known correlations like the Kormendy relation are projections of the photometric plane. The existence of the plane has interesting implications for bulge formation models.