In Ra, what happens if a player calls out Ra to start an auction and everyone else declines to bid?

In Mr. Reiner Knizia's timeless auction masterpiece Ra: when it is my turn to act, I voluntarily announce "Ra!" to forcibly open the auction. Going clockwise to all the other players, everyone chooses to pass. My question is: at this point, must I make a bid and take all the tiles on the board, or can I get them for free?