A 1940 self-portrait by famed Mexican artist Frida Kahlo has sold for $54.7m (41.8m, A$84.7m) at a New York art auction, setting a new top sale price for a work by any female artist. El sueno (La cama), or The Dream (The Bed), which depicts Kahlo asleep in a bed with a smiling skeleton wrapped in dynamite on the canopy above her, sold on Thursday night at a Sotheby's auction of surrealist art after four minutes of bidding.