• methods: statistical;
  • galaxies: evolution;
  • galaxies: formation;
  • galaxies: fundamental parameters


Early-type galaxies are characterized by many scaling relations. One of them, the so-called Fundamental Plane, is a relatively tight correlation between three variables and has resisted a clear physical understanding, despite many years of intensive research. Here, we show that the correlation between the three variables of the Fundamental Plane can be the artefact of the effect of another parameter influencing all, so that the Fundamental Plane may be understood as a confounding correlation. Indeed, the complexity of the physics of galaxies and of their evolution suggests that the main confounding parameter must be related to the level of diversification reached by the galaxies. Consequently, many scaling relations for galaxies are probably evolutionary correlations.