100NL: Flush on paired board river

[Aero1441]

SB: $96.75
BB: $105.20
UTG: $37.90
Hero (CO): $103.15
BTN: $36.00

Pre-Flop: 6 [img]/images/graemlins/heart.gif[/img] 5 [img]/images/graemlins/heart.gif[/img] dealt to Hero (CO)
UTG folds, Hero raises to $3.50, BTN folds, SB calls, BB folds

Flop: ($8.00) 4 [img]/images/graemlins/diamond.gif[/img] T [img]/images/graemlins/heart.gif[/img] 9 [img]/images/graemlins/heart.gif[/img] (2 Players)
SB checks, Hero bets $5.00, SB calls

Turn: ($18.00) 8 [img]/images/graemlins/diamond.gif[/img] (2 Players)
SB checks, Hero checks,

River: ($18.00) 8 [img]/images/graemlins/heart.gif[/img] (2 Players)
SB bets $18.00, Hero ?

Can someone please give me advice as to what to do on the river here? Do I get value from raising here? Or will I only get called by better hands and should I just call?