Mapping the Supernovae Driven Winds of the Large Magellanic Cloud in Hα Emission I

Abstract

Abstract We present the first spectroscopically resolved Hα emission map of the Large Magellanic Cloud’s (LMC) galactic wind. By combining new Wisconsin H-alpha Mapper observations (I Hα ≳ 10 mR) with existing H i 21 cm emission observations, we (1) mapped the LMC’s nearside galactic wind over a local standard of rest (LSR) velocity range of +50 ≤ v LSR ≤ +250 km s−1, (2) determined its morphology and extent, and (3) estimated its mass, outflow rate, and mass-loading factor. We observe Hα emission from this wind to typically 1° off the LMC’s H i disk. Kinematically, we find that the diffuse gas in the warm-ionized phase of this wind persists at both low (≲100 km s−1) and high (≳100 km s−1) velocities, relative to the LMC’s H i 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 ≈ 104 K) ionized phase of the nearside LMC outflow to be 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 , its mass-flow rate is , and its mass-loading factor is η ≈ 4.54. Our average mass-loading factor results are roughly a factor of 2.5 larger than previous Hα imaging and UV absorption line studies, suggesting that those studies are missing nearly half the gas in the outflows.