is there a proof of Jewish Christians in 1st and 2nd century AD?
I'd like to know whether there are proofs for the historicity of Acts accounts describing the Church in Jerusalem as vibrant and growing right after the Pentecost.
When I'm reading the historical websites, it appears that most if not all info is gleaned from the Church Fathers who are in disagreement with these believers.
And, very strangely, it appears that the Jewish believers in Christ met in synagogues (the very places of worship for non Messianic Jews). Which makes me wonder about the authenticity of the persecutions accounts. How could the non Messianic worship with the Christian Jews while persecuting them?
Also, why are there no Epistles to the Jewish Churches? Why are there no epistle to the Church in Jerusalem? Church in Galatia? Church in Samaria? And in between?
Are there PhD scholars who studied early Jewish Christianity?