Nobeyama 45 m mapping observations toward Orion A. I. Molecular outflows

Abstract

Abstract We conducted an exploration of ${}^{12}$CO molecular outflows in the Orion A giant molecular cloud to investigate outflow feedback using ${}^{12}$CO ($J = 1\!-\!0$) and ${}^{13}$CO ($J = 1\!-\!0$) data obtained by the Nobeyama 45 m telescope. In the region excluding the center of OMC 1, we identified 44 ${}^{12}$CO (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 ${}^{12}$CO 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 $1.6 \times 10^{2}\, M_{\odot }\:$km$\:$s$^{-1}$ and $1.5\times 10^{46}\:$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%.