An Ionized Outflow in Orion-KL Source I?

Melvyn Wright;Tomoya Hirota;Jan Forbrich;Richard Plambeck;John Bally;Ciriaco Goddi;Adam Ginsburg;Brett McGuire

2023-01-01

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Abstract

We present images at 6 and 14 GHz of Source I (SrcI) in the Kleinmann-Low Nebula in Orion. At higher frequencies, from 43 to 340 GHz, images of this source are dominated by thermal emission from dust in a 100 au diameter circumstellar disk, but at 6 and 14 GHz the emission is elongated along the minor axis of the disk, aligned with the SiO bipolar outflow from the central object. Gaussian fits to the 6, 14, 43, and 99 GHz images find a component along the disk minor axis whose flux and length vary with frequency consistent with free-free emission from an ionized outflow. The data favor a broad outflow from a disk wind, rather than a narrow ionized jet. SrcI was undetected in higher-resolution 5 GHz e-MERLIN observations obtained in 2021. The 5-6 GHz structure of SrcI may be resolved out by the high sidelobe structure of the e-MERLIN synthesized beam, or be time variable.