  As a framework for handling low Mach number limits we consider a notion of
measure-valued solution of the incompressible Euler system which explicitly
formulates the usually suppressed dependence on the pressure variable. We
clarify in which sense such a measure-valued solution is generated as a low
Mach limit and state sufficient conditions for this convergence. For the
special case of pressure-free solutions we are able to give such sufficient
conditions only on the incompressible solution itself. As a necessary condition
for low Mach limits we obtain a Jensen-type inequality. The same necessary
condition actually holds true for limits of weak solutions or vanishing
viscosity limits. We illustrate that this Jensen inequality is not trivially
fulfilled. Since measure-valued solutions in the classical sense are always
generated by weak solutions, this shows that our solution concept contains more
information and low Mach limits lead to a partial selection criterion for
incompressible solutions.
