Abstract
Abstract The Orion Kleinmann-Low nebula (Orion KL) is notoriously complex and exhibits a range of physical and chemical components. We conducted high-angular-resolution (subarcsecond) observations of 13CH3OH ν = 0 (∼0.″3 and ∼0.″7) and CH3CN ν 8 = 1 (∼0.″2 and ∼0.″9) line emission with the Atacama Large Millimeter/submillimeter Array (ALMA) to investigate Orion KL’s structure on small spatial scales (≤350 au). Gas kinematics, excitation temperatures, and column densities were derived from the molecular emission via a pixel-by-pixel spectral line fitting of the image cubes, enabling us to examine the small-scale variation of these parameters. Subregions of the Hot Core have a higher excitation temperature in a 0.″2 beam than in a 0.″9 beam, indicative of possible internal sources of heating. Furthermore, the velocity field includes a bipolar ∼7–8 km s−1 feature with a southeast–northwest orientation against the surrounding ∼4–5 km s−1 velocity field, which may be due to an outflow. We also find evidence of a possible source of internal heating toward the Northwest Clump, since the excitation temperature there is higher in a smaller beam versus a larger beam. Finally, the region southwest of the Hot Core (Hot Core-SW) presents itself as a particularly heterogeneous region bridging the Hot Core and Compact Ridge. Additional studies to identify the (hidden) sources of luminosity and heating within Orion KL are necessary to better understand the nebula and its chemistry.
Highlights
Molecules are useful tools for characterizing the physical structure of dense interstellar environments (e.g., Herbst & van Dishoeck 2009; Ginsburg et al 2017; Moscadelli et al 2018; Gieser et al 2019; Law et al 2021)
The velocity field exhibits an elongated structure centered on the Hot Core millimeter/submillimeter emission peak, which has been reported to be the site of an edge-on disk
This elongated structure, which is perpendicular to the edge-on disk, may be a lowvelocity outflow with an LSR velocity of ∼7–8 km s−1, which is slightly higher than the ambient velocity
Summary
Molecules are useful tools for characterizing the physical structure of dense interstellar environments (e.g., Herbst & van Dishoeck 2009; Ginsburg et al 2017; Moscadelli et al 2018; Gieser et al 2019; Law et al 2021). The results of high-angular-resolution imaging of Orion KL have generally focused on distinct regions or line emission peaks Such observations at various spatial scales are imperative to understanding the physical and chemical conditions of star-forming regions, and they reveal that there is still much to uncover in Orion KL. The angular resolutions (from 0 9 down to 0 2) were deliberately chosen to enable observations of small-scale, subregion variations in the chemical and physical conditions at the expense of resolving out extended emission that is already widespread in the existing literature Combining both molecular tracers in a single analysis is needed to characterize the wide range of environments in Orion KL, especially in light of the longstanding observations that nitrile and oxygen-bearing organic emission lines are kinematically and spatially distinct, even at 10–30′′ spatial resolution (e.g., Blake et al 1987; Crockett et al 2014b).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
