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

Abstract

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-minus free-free opacity, as in Mira variables, require a central star with >10^5 Lsun, 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.

16 pages, 1 table, 3 figures

References in corpus (1)

• OH maser disc and outflow in the Orion-BN/KL region

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• An ionized outflow in Orion-KL source I?
• Synthetic Polarization Maps of an Outflow Zone from Magnetohydrodynamic Simulations