ALMA Imaging of Gas and Dust in a Galaxy Protocluster at Redshift 5.3: [C II] Emission in "Typical" Galaxies and Dusty Starbursts ≈ 1 Billion Years after the Big Bang

We report interferometric imaging of [C II](^2 P_(3/2)→^2 P_(1/2)) and OH(^2Π_(1/2)J = 3/2→1/2) emission toward the center of the galaxy protocluster associated with the z = 5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [C II], OH, and rest-frame 157.7 μm continuum emission toward the SMG. The [C II](^2 P_(3/2)→^2 P_(1/2)) emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 × 10^(10) M_☉, and a star formation rate (SFR) surface density of Σ_(SFR) = 530 M_☉ yr^(–1) kpc^(–2). This suggests that AzTEC-3 forms stars at Σ^(SFR) approaching the Eddington limit for radiation pressure supported disks. We find that the OH emission is slightly blueshifted relative to the [C II] line, which may indicate a molecular outflow associated with the peak phase of the starburst. We also detect and dynamically resolve [C II](^2 P_(3/2)→^2 P_(1/2)) emission over a scale of 7.5 kpc toward a triplet of Lyman-break galaxies with moderate UV-based SFRs in the protocluster at ~95 kpc projected distance from the SMG. These galaxies are not detected in the continuum, suggesting far-infrared SFRs of 5, showing that ALMA can detect the interstellar medium in "typical" galaxies in the very early universe