A call here is entirely dependent on how large Biggy's calling range is.  Amazingly, if we can expect Biggy to call with ATC a shove is actually a losing move.

While A9 is roughly a 60% favorite against a random holding (60.773% to be exact), the fact is Biggy simply has too big of a stack - even if we manage to double up we would still be at a 5:3 disadvantage chip-wise, and then of course there's the remote chance of the short stack doubling/tripling up back into the game.

If we were to narrow villain's calling range to any pair, any ace, and any two paint, we are reducing our win rate when the hand plays out to just below 50%, but because villain will have one of these holdings so few times it is actually profitable to shove - the money we pick up when villain folds more than accounts for when he calls and we have to get a little lucky.

This hand ultimately comes down to how tight of a calling range villain has, however this hand is more interesting because in a SnG you should generally err on the side of aggression in the end-game.  In this case, you should err on the side of caution due to villain's massive chip lead and the jump in payout between 2nd and 3rd.