Molecular Superbubbles and Outflows from the Starburst Galaxy NGC 2146

Abstract

Abstract We present results from a deep (1$\sigma$$=$ 5.7 mJy beam$^{-1}$ per 20.8 kms$^{-1}$ velocity channel) $^{12}$CO(1–0) interferometric observation of the central 60$^{\prime\prime}$ region of the nearby edge-on starburst galaxy NGC 2146, observed with the Nobeyama Millimeter Array. Two diffuse expanding molecular superbubbles and one molecular outflow were successfully detected. One molecular superbubble, with a size of $\sim$1 kpc and an expansion velocity of $\sim$50 kms$^{-1}$, is located below the galactic disk; a second molecular superbubble, with a size of $\sim$700 pc and an expansion velocity of $\sim$35 kms$^{-1}$, is also seen in the position-velocity diagram; the molecular outflow is located above the galactic disk with an extent of $\sim$2 kpc, expanding with a velocity of up to $\sim$200 kms$^{-1}$. The molecular outflow has an arc-like structure, and is located at the front edge of the soft X-ray outflow. In addition, the kinetic energy ($\sim$3 $\times$ 10$^{55}$erg) and the pressure ($\sim$1 $\times$ 10$^{-12\pm1}$dyncm$^{-2}$) of the molecular outflow are comparable to, or smaller than, that of the hot thermal plasma, suggesting that the hot plasma pushes the molecular gas out from the galactic disk. Inside the $\sim$1 kpc size molecular superbubble, diffuse soft X-ray emission seems to exist. However, since the superbubble lies behind the inclined galactic disk, it is largely absorbed by the molecular gas.