Spatially Resolved Molecular Interstellar Medium in a z = 6.6 Quasar Host Galaxy

Abstract

We present high spatial resolution (∼0.″4, 2.2 kpc) observations of the CO(6−5), CO(7−6), and [C i]369 μm lines and dust continuum emission from the interstellar medium (ISM) in the host galaxy of the quasar J0305−3150 at z = 6.6. These, together with archival [C ii]158 μm data at a comparable spatial resolution, enable studies of the spatial distribution and kinematics between the ISM in different phases. When comparing the radial profiles of CO, [C ii]158 μm, and the dust continuum, we find that the CO and dust continuum exhibit similar spatial distributions, both of which are less extended than the [C ii]158 μm, indicating that the CO and dust continuum are tracing the same gas component, while the [C ii]158 μm is tracing a more extended one. In addition, we derive the radial profiles of the [C ii]158 μm/CO, [C ii]158 μm/far-infrared (FIR), CO/FIR, and dust continuum S 98.7 GHz/S 258.1 GHz ratios. We find a decreasing S 98.7 GHz/S 258.1 GHz ratio with radius, possibly indicating a decrease of dust optical depth with increasing radius. We also detect some of the ISM lines and continuum emission in the companion galaxies previously discovered in the field around J0305−3150. Through comparing the line-to-line and line-to-FIR ratios, we find no significant differences between the quasar and its companion galaxies.