ALMA observed OH⁺ line. Left panel: OH⁺ emission line velocity-integrated map. The white plus sign is the HST quasar position. The shape of the restoring beam with a FWHM size of × is plotted in the bottom-left corner. The contour levels in black are [3, 4, 5] × rms_{OH⁺_em}, where rms_{OH⁺_em} = 0.012 Jy beam⁻¹ km s⁻¹. The peak flux density is 0.066 ± 0.012 Jy beam⁻¹ km s⁻¹. The overplotted dashed white contours are from the OH⁺ absorption line, with contour levels of [−3, −2] × rms_{OH⁺_ab}, where rms_{OH⁺_ab} = 0.008 Jy beam⁻¹ km s⁻¹. Right panel: OH⁺ line spectrum (black histogram) overplotted with the best-fit triple-Gaussian profile (red line). The dashed and dotted blue lines present the blueward and redward emission components, respectively, and the dash-dotted blue line represent the absorption component. The spectrum is extracted from the 2σ region of the source emitting area in the OH⁺ intensity map. The LSRK velocity scale is relative to the [C II] redshift from our ALMA Cycle 0 observations (Wang et al. 2013). The spectral resolution is 31.25 MHz, corresponding to 64 km s⁻¹. The rms of the spectrum is 0.05 mJy and is shown as a black bar. The green bar indicates the full width at zero intensity of the [C II] line, which is roughly consistent with that of the best-fit model for the OH⁺ emission line.