Mapping the Supernovae Driven Winds of the Large Magellanic Cloud in H$\hat{I}\pm$ 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 ($I_{\mathrm{H}\hat{\mathrm{I}}\pm }\gtrsim 10\mathrm{mR}$) 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 $+50\le {\mathrm{v}}_{\mathrm{LSR}}\le +250\mathrm{km}{\mathrm{s}}^{-1}$, (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 ($\lesssim 100\mathrm{km}{\mathrm{s}}^{-1}$) and high ($\gtrsim 100\mathrm{km}{\mathrm{s}}^{-1}$) 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 ($T_e\approx 10^4\mathrm{K}$) ionized phase of the near-side LMC outflow to be $\log \left(M_{\mathrm{ionized}}/M_{\odot }\right)=7.51\pm 0.15$ 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 $\log \left(M_{\mathrm{total}}/M_{\odot }\right)=7.93$, its mass-flow rate is ${\dot{M}}_{\mathrm{outflow}}\approx 1.43M_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$, and its mass-loading factor is $\hat{I}\cdot \approx 4.54$. 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.

19 pages, 9 figures