Detection of a large massive circumstellar disk around a high-mass young stellar object in the Carina Nebula

Context. The characterization of circumstellar disks around young stellar objects can provide important information about the process of star formation and the possible formation of planetary systems.
Aims: We investigate the spatial structure and the spectral energy distribution of a newly discovered edge-on circumstellar disk around an optically invisible young stellar object that is embedded in a dark cloud in the Carina Nebula.
Methods: The disk object was serendipitously discovered in our deep near-IR imaging survey of the Carina Nebula obtained with HAWK-I at the ESO VLT. Whereas the object was detected as an apparently point-like source in earlier infrared observations, only the superb image quality (FWHM ≈ 0.5'') of the HAWK-I data could reveal, for the first time, the peculiar morphology of the object. It consists of a very red point-like central source that is surrounded by a roughly spherical nebula, which is intersected by a remarkable dark lane through the center. We construct the spectral energy distribution of the object from 1 μm to 870 μm and perform a detailed radiative transfer modeling of the spectral energy distribution and the source morphology.
Results: The observed object morphology in the near-IR images clearly suggests a young stellar object that is embedded in an extended, roughly spherical envelope and surrounded by a large circumstellar disk with a diameter of ≈5500 AU that is seen nearly edge-on. The radiative transfer modeling shows that the central object is highly luminous and thus must be a massive young stellar object, most likely in the range 10-15 M_⊙. The circumstellar disk has a mass of about 2 M_⊙.
Conclusions: The disk object in Carina is one of the most massive young stellar objects for which a circumstellar disk has been detected so far. The size and mass of the disk are very large compared to the corresponding values found for most other similar objects. These results support the assumption that 10-15 M_⊙ stars can form via accretion from a circumstellar disk.

The near-infrared observations for this project were collected with the HAWK-I instrument on the VLT at Paranal Observatory, Chile, under ESO program 60.A-9284(K).