25NL; AJ vs unkown SB; how would you play this?

[vanoff]

Party Poker - No Limit Hold'em Cash Game - $0.10/$0.25 Blinds - 5 Players - (LegoPoker HH Converter)

SB: $18.80
BB: $25.01
UTG: $28.60
<font color="black">Hero (CO): $40.80</font>
BTN: $21.05

<font color="black">Preflop:</font> Hero is dealt A[img]/images/graemlins/club.gif[/img] J[img]/images/graemlins/diamond.gif[/img] (5 Players)
UTG folds, <font color="red">Hero raises to $1.00</font>, BTN folds, SB calls $0.90, BB folds

<font color="black">Flop:</font> ($2.25) T[img]/images/graemlins/heart.gif[/img] 3[img]/images/graemlins/club.gif[/img] 5[img]/images/graemlins/diamond.gif[/img] (2 Players)
<font color="red">SB bets $1.00</font>, <font color="red">Hero raises to $3.50</font>, SB calls $2.50

<font color="black">Turn:</font> ($9.25) A[img]/images/graemlins/heart.gif[/img] (2 Players)
<font color="red">SB bets $2.00</font>, <font color="red">Hero raises to $7.00</font>, SB calls $5.00

<font color="black">River:</font> ($23.25) K[img]/images/graemlins/heart.gif[/img] (2 Players)
SB checks, Hero??

How would you guys play this hand vs an unknown who just sat down?