Postdoc salaries/taxes in California (Caltech) for foreigner I have seen some confusing information online. I am looking into postdoc positions at Caltech (Pasadena, CA). From my understanding, the annual salaries are somewhere in the 55k - 60 k range. What kind of taxes apply, though? I've seen conflicting information, and am quite confused.
Here it seems that some of Caltech are exempt from federal tax, but I am not sure if this applies to postdoc researchers.
Also, how does one being a foreigner (with a work VISA) affect taxation?
The National Postdoc Association has an Overview of Tax Issues for Postdocs that may be a good starting point.

Here it seems that some of Caltech are exempt from federal tax, but I am not sure if this applies to postdoc researchers.

This just means that Caltech itself is exempt from paying income tax. By default (that is, unless there's a tax treaty), a postdoc receiving money to cover living expenses will pay tax on their income. In California there would be both federal and state income tax.

Also, how does one being a foreigner (with a work VISA) affect taxation?

This can depend on whether there is a relevant tax treaty or not, and how long they've been present inside US borders. See e.g. International Postdoc Survival Guide - Beginner's Guide to Income Taxes for International Postdocs for resources.