Imaging the Ionized Disk of the High-Mass Protostar Orion–I

We have imaged the enigmatic radio source-I (Orion–I) in the Orion-KL nebula with the VLA at 43 GHz with 34 mas angular resolution. The continuum emission is highly elongated and is consistent with that expected from a nearly edge-on disk. The high brightness and lack of strong molecular lines from Orion– I can be used to argue against emission from dust. Collisional ionization and H free-free opacity, as in Mira variables, require a central star with > ∼ 10 5 L⊙, which is greater than infrared observations allow. However, if significant local heating associated with accretion occurs, lower total luminosities are possible. Alternatively, photo-ionization from an early B-type star and p/e bremsstrahlung can explain our observations, and Orion–I may be an example of ionized accretion disk surrounding a forming massive star. Such accretion disks may not be able to form planets efficiently. Subject headings: infrared: stars — ISM: individual (Orion Kleinmann-Low) — stars: individual (I,IRc 2) — stars: formation — planetary systems: formation