Fixed subgroups in Artin groups

We study fixed subgroups of automorphisms of any large-type Artin group A_{\Gamma} . We define a natural subgroup \operatorname{Aut}_{\Gamma}(A_{\Gamma}) of \operatorname{Aut}(A_{\Gamma}) , and for every \gamma \in \operatorname{Aut}_{\Gamma}(A_{\Gamma}) , we find the isomorphism type of \operatorname{Fix}(\gamma) and a generating set for a finite index subgroup. We show that \operatorname{Fix}(\gamma) is a finitely generated Artin group, with a uniform bound on the rank in terms of the number of vertices of \Gamma . Finally, we provide a natural geometric characterisation of the subgroup \operatorname{Aut}_{\Gamma}(A_{\Gamma}) , which informally is the maximal subgroup of \operatorname{Aut}(A_{\Gamma}) leaving the Deligne complex of A_{\Gamma} invariant.