2006ApJ...642..933H

The three-carbon keto ring cyclopropenone (c-H₂C₃O) has been detected largely in absorption with the 100 m Green Bank Telescope (GBT) toward the star-forming region Sagittarius B2(N) by means of a number of rotational transitions between energy levels that have energies less than 10 K. Previous negative results from searches for interstellar c-H₂C₃O by other investigators attempting to detect rotational transitions that have energy levels ∼10 K or greater indicate no significant hot core component. Thus, we conclude that only the low-energy levels of c-H₂C₃O are populated because the molecule state temperature is low, suggesting that c-H₂C₃O resides in a star-forming core halo region that has a widespread arcminute spatial scale. Toward Sagittarius B2(N), the GBT was also used to observe the previously reported, spatially ubiquitous, three-carbon ring cyclopropenylidene (c-C₃H₂ ), which has a divalent carbon that makes it highly reactive in the laboratory. The presence of both c-C₃H₂and c-H₂C₃O toward Sagittarius B2(N) suggests that gas-phase oxygen addition may account for the synthesis of c-H₂C₃O from c-C₃H₂. We also searched for but did not detect the three-carbon sugar glyceraldehyde (CH₂OHCHOHCHO).