如何将soql查询结果放入map<Id,String>

错误:编译错误:找到的初始值设定项类型列表无效 映射:应为具有相同键和值类型的映射,或 第7行第25列的有效SObject列表

trigger insertUpdateOwnerToSalesRep on Account (after insert, before update) {
    if (trigger.IsAfter && trigger.IsUpdate) {
        List<User> lstUser =[select id,name from User where Id in:(Trigger.NewMap).keySet()];

        //Map<Id,String> ac=new Map<Id,String>([]);
        Map<ID, String> m = new Map<ID, String>([select id,name from User where Id in:(Trigger.NewMap).keySet()]);
        for(Account ac:Trigger.New) {
            System.debug('^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\t'+ac.ownerid);
            if (ac.owner!=null) {
                User user=ac.owner;
                System.debug('!!!!!!!!!!!!!!\t'+user);
                //ac.Sales_Rep__c=ac.owner.userName;
            }
        }
    }
}