History is not a science, and there are no history "authorities" in any hierarchical sense. There are many individual practitioners of history (the "discipline") and there are various national and international societies (the American Historical Association, for example) but they do not generally weigh in on "confirming historical facts." (They might, occasionally, issue a "professional statement," but these are usually about things like the conduct of professionalism, not individual facts.) And there are of course institutions that organize, fund, and reward historical work, and you can think of these as a form of "authority," but they do not have anything like legal power or even professional power. They cannot get you fired, they cannot get you hired; at most they can control who gets their funding and who does not.

Historians disagree on facts and interpretations all the time. Neither history (nor science) couches its arguments on "authority," but on evidence and argument, under the (perhaps naive) belief that it is the argument by experts over these things that determines, ultimately, what is most likely to be true.

There have been grave disagreements over both content and method in history over the years, including over who has the "authority" to even speak as a historian. But there is no centralized authority; even these professional organizations are simply made up of other historians.

For a very nice discussion of the disputes about all of this in the American context, see esp. Peter Novick, That Noble Dream: The 'Objectivity Question' and the American Historical Profession, which is all about how historians have parsed over the questions of objectivity and "facts," and the roles that various institutions and organizations have played in this.

Authority in the context of historical research is never absolute. Every written source has its biases and historiography; every artifact has its provenance, route of transmission; every scientific measurement its interpretation. When historians talk about "the authority" of a given work, it is usually based on its primacy as a valued source; it does not mean that a given source is always correct in all accounts.

Everything, in other words, is subject to evaluation and re-evaluation. There is no single ultimate authority, although there are many individuals who because of their wealth of knowledge and long study of a given subject are widely respected in their interpretation and presentation of the evidence.

To take an example from my personal field of study, S. T. Joshi is widely considered an authority on H. P. Lovecraft, and his most extensive biography I Am Providence (2011) is considered the most authoritative biography of Lovecraft yet written. That does not mean that Joshi knows everything about Lovecraft, or that everything written in the book is always and forever correct. There is always the possibility that some new batch of letters, documents, or other evidence might come to light that revises how we think about Lovecraft. Yet Joshi is extremely knowledgable on Lovecraft, has studied his life and works in-depth for decades, and the narrative of his life presented in I Am Providence is well-supported by primary and secondary sources.