2023ApJ...948..118S

The Large Magellanic Cloud (LMC) has an extensive Hα emission halo that traces an extended, warm ionized component of its interstellar medium. Using the Wisconsin Hα Mapper telescope, we present the first kinematic Hα survey of an extensive region around the LMC, from (ℓ, b) = (264.°5, - 45.°5) to (295.°5, - 19.°5), covering +150 ≤ v_LSR ≤ + 390 km s^–1. We find that ionized hydrogen exists throughout the galaxy and extends several degrees beyond detected neutral hydrogen emission $(\mathrm{log}\left({N}_{{\rm{H}}\,{\rm\small{I}}/{\mathrm{cm}}^{-2}}\right)\approx 18.3)$ as traced by 21 cm in current surveys. Using the column density structure of the neutral gas and stellar line-of-sight depths as a guide, we estimate the upper limit mass of the ionized component of the LMC to be roughly M_ionized ≈ (0.6-1.8) × 10⁹M_☉, which is comparable to the total neutral atomic gas mass in the same region (M_neutral ≈ 0.76-0.85 × 10⁹M_☉). Considering only the atomic phases, we find M_ionized/M_{ionized+neutral}, to be 46%-68% throughout the LMC and its extended halo. Additionally, we find an ionized gas cloud that extends off of the LMC at (ℓ, b) ≈ (285°, - 28°) into a region previously identified as the Leading Arm complex. This gas is moving at a similar line-of-sight velocity as the LMC and has M_ionized/M_{ionized+neutral} = 13%-51%. This study, combined with previous studies of the SMC and extended structures of the Magellanic Clouds, continues to suggest that warm, ionized gas is as massive and dynamically important as the neutral gas in the Magellanic System.