AQo gets raised on A hight flop

[gopnik]

I am switching from limit, so, please bear with me if my questions are boring.

Unknown villain.

PokerStars No-Limit Hold'em, $0.50 BB (8 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

SB ($37.45)
BB ($26.40)
UTG ($40.95)
UTG+1 ($45.05)
Hero ($27.90)
MP2 ($49.25)
CO ($59.85)
Button ($33.20)

Preflop: Hero is MP1 with A[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">1 fold</font>, UTG+1 calls $0.50, <font color="#CC3333">Hero raises to $1.5</font>, <font color="#666666">2 folds</font>, Button calls $1.50, <font color="#666666">1 fold</font>, BB calls $1, UTG+1 calls $1.

Flop: ($6.25) A[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
BB checks, UTG+1 checks, <font color="#CC3333">Hero bets $3</font>, <font color="#CC3333">Button raises to $6</font>, BB folds, UTG+1 folds, Hero?


What's my plan?