how to emit events from a factory

Inject $rootScope instead of $scope and then emit it on the $rootScope.

myApp.factory('myFactory', ['$rootScope', function ($rootScope) {
    $rootScope.$emit("myEvent", myEventParams);
}]);

Factories don’t have access to the current controller/directive scope because there isn’t one. They do have access to the root of the application though and that’s why $rootScope is available.