A new look at simple inhomogeneous chemical evolution

A rudimentary, one-zone, closed-box model for inhomogeneous chemical evolut ion is offered as an alternative reference model, distinct from the Simple Model, in the limit off no mixing. The metallicity distribution functions ( MDFs) of Galactic halo and bulge stars can be matched by varying a single e volutionary parameter, ne. Q is the filling factor of contaminating regions , and n is the number of star-forming generations. Therefore, Q and n have equivalent roles, and combinations of n and Q yield systems with different metallicities at any given age. The model also revises the interpretation o f observed MDFs. Unevolved systems probe the metallicity distribution f(z) of parent enrichment events; for example, the high-metallicity tail of the halo distribution agrees with a power-law f(z).