We report the existence of spiral arms in the recently formed gaseous and dusty disk of the closest giant elliptical , NGC 5128 ( Centaurus A ) , using high resolution ^ { 12 } CO ( 2–1 ) observations of the central 3′ ( 3 kpc ) obtained with the Submillimeter Array ( SMA ) .
This provides evidence that spiral-like features can develop within ellipticals if enough cold gas exists .
We elucidate the distribution and kinematics of the molecular gas in this region with a resolution of 4 \farcs 4 \times 1 \farcs 9 ( 80 pc \times 40 pc ) .
The spiral arms extend from the circumnuclear gas at a radius of 200 pc to at least 1 kiloparsec .
The general properties of the arms are similar to those in spiral galaxies : they are trailing , their width is \sim 500 \pm 200 pc , and the pitch angle is \sim 20 ^ { o } .
From independent estimates of the time when the HI-rich galaxy merger occurred , we infer that the formation of spiral arms occured on a time scale of less than \sim 10 ^ { 8 } yr .
The formation of spiral arms increases the gas density and thus the star formation efficiency in the early stages of the formation of a disk .