Mapping the Supernovae Driven Winds of the Large Magellanic Cloud in H$\alpha$ Emission I

Abstract

We present the first spectroscopically resolved \ha\ emission map of the Large Magellanic Cloud's (LMC) galactic wind. By combining new Wisconsin H-alpha Mapper (WHAM) observations ($I_{\rm H\alpha}\gtrsim10~{\rm mR}$) with existing \hicm\ emission observations, we have (1) mapped the LMC's near-side galactic wind over a local standard of rest (LSR) velocity range of $+50\le\rm v_{LSR}\le+250~{\rm km}~{\rm s}^{-1}$, (2) determined its morphology and extent, and (3) estimated its mass, outflow rate, and mass-loading factor. We observe \ha\ emission from this wind to typically 1-degree off the LMC's \hi\ disk. Kinematically, we find that the diffuse gas in the warm-ionized phase of this wind persists at both low ($\lesssim100~{\rm km}~{\rm s}^{-1}$) and high ($\gtrsim100~{\rm km}~{\rm s}^{-1}$) velocities, relative to the LMC's \hi\ disk. Furthermore, we find that the high-velocity component spatially aligns with the most intense star-forming region, 30~Doradus. We, therefore, conclude that this high-velocity material traces an active outflow. We estimate the mass of the warm ($T_e\approx10^4~\rm K$) ionized phase of the near-side LMC outflow to be $\log{\left(M_{\rm ionized}/M_\odot\right)=7.51\pm0.15}$ for the combined low and high velocity components. Assuming an ionization fraction of 75\% and that the wind is symmetrical about the LMC disk, we estimate that its total (neutral and ionized) mass is $\log{\left(M_{\rm total}/M_\odot\right)=7.93}$, its mass-flow rate is $\dot{M}_{\rm outflow}\approx1.43~M_\odot~\rm yr^{-1}$, and its mass-loading factor is $\eta\approx4.54$. Our average mass-loading factor results are roughly a factor of 2.5 larger than previous \ha\ imaging and UV~absorption line studies, suggesting that those studies are missing nearly half the gas in the outflows.