ALMA observed [C II] line. Left panel: [C II] velocity-integrated map. The white plus sign is the Hubble Space Telescope (HST) quasar position (RA of 23:10:38.90; Dec of 18:55:19.85). The shape of the restoring beam with a FWHM size of × is plotted in the bottom-left corner. The contour levels are [−3, 3, 6, 9, 12, 15] × rms_[C II], where rms_[C II] = 0.035 Jy beam⁻¹ km s⁻¹. Middle panel: [C II] velocity map produced using pixels above 4σ in the channel maps. The black plus sign is the HST quasar position. A clear velocity gradient can be seen. Right panel: [C II] line spectrum (black histogram) overplotted with the best-fit Gaussian profiles. The spectrum is extracted from the 2σ region of the source emitting area in the [C II] intensity map. The solid blue line presents the best-fit single Gaussian model. The solid red line represents the best-fit double-Gaussian model, and the dashed and dotted red lines are for each of the double Gaussians. The kinematic local standard of rest (LSRK) velocity scale is relative to the [C II] redshift from our ALMA Cycle 0 observations (Wang et al. 2013). The spectral resolution is 15.625 MHz, corresponding to 17 km s⁻¹. The rms of the spectrum measured using the line-free spectrum is 0.65 mJy and is shown as a black bar. The [C II] spectral profile is asymmetric, with enhancement on the red side. The green bar indicates the velocity range of the OH⁺ absorption.