At this vulnerability, partner would open 1♠ with 10 or more HCP. In addition, you play NAMYATS, with the following requirements:
8 1/2 to 9 playing tricks.
No more than one side suit with two quick losers.
So, partner has less than 10 HCP and his hand does not meet our requirements for a NAMYATS opener. By the way, if he opened NAMYATS, his HCP holding would be irrelevant.
Do you pass, move towards slam or bid slam?
Edit: Nonvul (the hand diagram would have a red field under the compass directions if one or both sides were vulnerable).