Multiphase ISM in the z=5.7 Hyperluminous Starburst SPT 0346-52

With sigma(SFR) similar to 4200 M (circle dot) yr(-1) kpc(-2), SPT 0346-52 (z = 5.7) is the most intensely star-forming galaxy discovered by the South Pole Telescope. In this paper, we expand on previous spatially resolved studies, using ALMA observations of dust continuum, [N ii] 205 mu m, [C ii] 158 mu m, [O i] 146 mu m, and undetected [N ii] 122 mu m and [O i] 63 mu m emission to study the multiphase interstellar medium (ISM) in SPT 0346-52. We use pixelated, visibility-based lens modeling to reconstruct the source-plane emission. We also model the source-plane emission using the photoionization code cloudy and find a supersolar metallicity system. We calculate T (dust) = 48.3 K and lambda (peak) = 80 mu m and see line deficits in all five lines. The ionized gas is less dense than comparable galaxies, with n ( e ) < 32 cm(-3), while similar to 20% of the [C ii] 158 mu m emission originates from the ionized phase of the ISM. We also calculate the masses of several phases of the ISM. We find that molecular gas dominates the mass of the ISM in SPT 0346-52, with the molecular gas mass similar to 4x higher than the neutral atomic gas mass and similar to 100x higher than the ionized gas mass.