There is only silence after Xarz's words, a silence that, for him, seems like a long time. He knows that every second ticking by is a wait for the judgment from the man in front of him. This is actually a gamble he has taken himself, choosing to surrender to Aldrian rather than attempting to escape on his own.
There are a few reasons why he did not choose to escape after betraying Rulleus. The first is that he is not even confident he could escape from Aldrian. If he chose to flee, then Aldrian would see him in an even more negative way and would undoubtedly kill him in the end.
It is better to show his 'sincerity' through surrender, which holds a higher probability of survival.
