I'm an undergraduate student (United States) majoring in X, applying to PhD programs with a research focus in subfields Y and Z.
I conjecture that the best universities for Y and the best universities for Z are not necessarily the same, and I want to narrow down my PhD applications to universities that are known for one or both of these subfields.
None of the professors at my university's X department do much research in either Y or Z, and they seem to not have the greatest idea where I should apply - I usually get generic answers like Prestigious University U, which may or may not be what I'm looking for.
The other concern is that I've taken a few graduate classes regarding Y and Z, but in no way am I fluent in the fields, nor have I done direct research in these fields. As such, it would be difficult for me to attempt to read research papers about Y and Z to try to back out which universities produce the best work.
How might I go about finding the strongest programs in Y and Z?