Did prominent byzantine families existed in Syria and Egypt after Arabian conquest?
But of course. There was no mass expulsion nor any ethnic cleanising. Prominent Roman families remained where they lived, but of course slowly converted to Islam in due course. But the Arab conquerors were keen to use what they found, be it economically, politically and in governing.
Do you know any reserarches on this theme?
Several, but I'm not at home right know. I'll have a look this evening.
I would suggest: Framing the Early Middle Ages by Chris Wickham or the Inheritence of Rome also by Chris Wickham