Nobeyama 45-m Mapping Observations toward Orion A.I. Molecular Outflows

TL;DR

This study systematically mapped 12CO outflows in Orion A, estimating their physical properties and assessing their role in cloud turbulence, revealing outflows alone cannot sustain turbulence without high energy conversion efficiency.

Contribution

First systematic survey of 12CO outflows in Orion A using automated methods, providing detailed outflow properties and feedback analysis.

Findings

44 outflows identified, including 17 new detections

Outflow momentum and energy are significant but insufficient to sustain turbulence alone

Outflows' energy ejection rate exceeds turbulence dissipation rate, but efficiency must be high

Abstract

We conducted an exploration of 12CO molecular outflows in the Orion A giant molecular cloud to investigate outflow feedback using 12CO (J = 1-0) and 13CO (J = 1-0) data obtained by the Nobeyama 45-m telescope. In the region excluding the center of OMC 1, we identified 44 12CO (including 17 newly detected) outflows based on the unbiased and systematic procedure of automatically determining the velocity range of the outflows and separating the cloud and outflow components. The optical depth of the 12CO emission in the detected outflows is estimated to be approximately 5. The total momentum and energy of the outflows, corrected for optical depth, are estimated to be 1.6 x 10 2 M km s-1 and 1.5 x 10 46 erg, respectively. The momentum and energy ejection rate of the outflows are estimated to be 36% and 235% of the momentum and energy dissipation rates of the cloud turbulence, respectively. Furthermore, the ejection rates of the outflows are comparable to those of the expanding molecular shells estimated by Feddersen et al. (2018, ApJ, 862, 121). Cloud turbulence cannot be sustained by the outflows and shells unless the energy conversion efficiency is as high as 20%.