On inverse semigroup $C^{\ast }$-algebras and crossed products

We describe the $C^{\ast }$-algebra of an $E$-unitary or strongly 0-$E$-unitary inverse semigroup as the partial crossed product of a commutative $C^{\ast }$-algebra by the maximal group image of the inverse semigroup. We give a similar result for the $C^{\ast }$-algebra of the tight groupoid of an inverse semigroup. We also study conditions on a groupoid $C^{\ast }$-algebra to be Morita equivalent to a full crossed product of a commutative $C^{\ast }$-algebra with an inverse semigroup, generalizing results of Khoshkam and Skandalis for crossed products with groups.