Do readers consider the passive voice as more authoritative? In the middle of the last century (roughly from the 20s-70s) the passive voice dominated scientific writing; or should it be said that scientific writing was dominated by the passive voice? 

Nowadays, there is pushback against the passive voice with (noted scientists like) Robert May saying that "these days, use of the passive voice in a research paper is, more often than not, the hallmark of second rate work." Moore (2000) even argues (from anecdotal evidence) that your scientific work might have less impact if you rely on the passive voice (among other factors of poor rhetoric).

However, the passive voice is still preferred (or at least used) by many scientists. This is occasionally explained by the assertion that the passive voice is more objective or seems more authoritative. Is there any empirical literature on this?

Does a text appear more objective or authoritative if it is written in the passive voice? Does it appear more 'scientific'? Does it affect the impact of the work (or proxies like citation count)? Is this effect context (say, science vs. law vs. politics, etc) dependent?
Short answer
I haven't found scientific literature on it. Non-scientific sources generally do seem to acknowledge that the passive voice radiates authority.  

Background
To answer the question if there's scientific research on this topic - I wasn't able to find anything of value on an, admittedly, quite cursory Google Scholar search. 

In fact, given the high element of subjectivity in 'finding a text sounding authoritative', I think this question may be more suitable for Writing.SE. However, since the question is heavily upvoted, and since it does indeed touch on the Psychological Sciences, I'll give my two-cents worth based on two non-scientific, non-peer-reviewed book quotes and a regular website entry.

Online Writing Training says:


  One of the main reasons why the passive voice gets such a bad name is that many [] writers overuse it to make their writing seem more formal and authoritative. The result is often turgid, difficult-to-read prose. Take this example


Lebrun Jean-luc says in his book Scientific Writing 2.0: A Reader And Writer's Guide


  [The] passive voice [] give[s] the paper a more authoritative disembodies voice,...


As a last example, William M. Vatavuk states in his book Marketing Yourself with Technical Writing: A Guide for Today's Professionals:


  Maybe technical writers feel that  that the passive voice is more formal, more professional sounding, and that it gives their writing a more authoritative ring...


I think that last quote is important: people feel that way, but it's entirely a subjective thing; some may find the passive voice boring, others may regard it as authoritative.