Detection of Star Formation in the Unusually Cold Giant Molecular Cloud G216-2.5

The giant molecular cloud G216-2.5, also known as Maddalena's cloud or the Maddalena-Thaddeus cloud, is distinguished by an unusual combination of high gas mass (1-6 × 10⁵ M _sun), low kinetic temperatures (10 K), and the lack of bright far-IR emission. Although star formation has been detected in neighboring satellite clouds, little evidence for star formation has been found in the main body of this cloud. Using a combination of mid-IR observations with the IRAC and Multiband Imaging Photometer for Spitzer instruments onboard the Spitzer Space Telescope, and near-IR images taken with the Flamingos camera on the KPNO 2.1 m telescope, we identify a population of 41 young stars with disks and 33 protostars in the center of the cloud. Most of the young stellar objects are coincident with a filamentary structure of dense gas detected in CS (2 → 1). These observations show that the main body of G216 is actively forming stars, although at a low stellar density comparable to that found in the Taurus cloud.

Based on observations made with ESO telescopes at the La Silla Observatory.