Dry (i.e. dissipationless) merging has been proposed as the main driver of
the observed size evolution of early-type galaxies (ETGs). The actual role of
this mechanism is questioned by the tightness of the local stellar mass-size
relation of ETGs. Combining this observed scaling law with simple merging
models, which should bracket cosmologically motivated merging histories, we
draw the following conclusions: 1) local massive ETGs can have assembled at
most ~45% of their stellar mass via dry mergers; 2) extreme fine tuning is
required for this to be the case.Comment: 4 pages, 1 figure, 1 table. To appear in "Advances in Computational
Astrophysics: methods, tools and outcomes", ASP Conference Series, R.
Capuzzo-Dolcetta, M. Limongi and A. Tornamb\`e ed
