On a solution operator for differential equations of infinity order on convex sets

Let $Q$ be a convex (not necessarily bounded) set in $\mathbb C$ with the nonempty interior which has a countable neighborhood base of convex domains; $A(Q)$ be the space of germs of all analytic functions on $Q$ with its natural inductive limit topology. Necessary and sufficient conditions under which a fixed nonzero differential operator of infinite order with constant coefficients which acts in $A(Q)$ has a continuous linear right inverse are established. This criterion is obtained in terms of the existence of a special family of subharmonic functions.