[Lonesome in Massachussets]

It's called argumentum ad verecundiam, "appeal to authority", a potential form of logical fallacy. It's not necessarily a logical fallacy, courts accept expert testimony all the time. If I get medical advice from my doctor and from my sister-in-law, I tend to trust my doctor more. If I discover that my doctor is taking Hawaiian vacations paid for by the company making the medication he is prescribing, I might reconsider.

If some crackpot mathematics professor from Pisa tells me that the sun and the stars in the heavenly vault stand still, and the earth whirls around the poles while circling the sun, against the opinion of my own senses and that of the best astrologers and contrary to Holy Scripture, I might not be inclined to accept his view.

[allmendream]

Yes, an authority on a subject has to convince based upon an explanation of the evidence not “because I am an authority”.

If a well regarded historian says something is the most likely explanation based upon documents A, B and C - he is not making an argument from authority - he IS an authority - but he is making an argument based upon the evidence.

Those without any expertise who want to hold a contrary view DESPITE the evidence are likely to make the fallacious argument that he is simply making an argument from authority. But they are wrong to do so.