Galois representations associated with unitary groups over Q

We show that a cuspidal automorphic representation pi = circle times(l <=infinity) pi(l) of a unitary similitude group GU(a, b)(/Q) with archimedean component pi(infinity) in a regular discrete series has an associated (a + b)-dimensional p-adic Galois representation with Frobenius eigenvalues given by the local base change parameters for all primes l such that pi(l) and GU(a, b) are unramified.