Integrated aperture spectra for HD1 around the expected frequency of the [C II] 158 μm (top panel) and [O III] 88 μm (bottom panel) emission lines. To easily compare the spectra extracted within apertures of different size, spectra are presented in terms of signal-to-noise ratio rather than actual flux density. For the [C II] 158 μm emission we adopt apertures of and , corresponding to a similar size to the beam and 1.25 times the beam of the ALMA band 4 data, respectively. In the bottom panel we adopt an aperture of and , corresponding to roughly the beam size and the aperture adopted in Harikane et al. (2022) for the same data, respectively. The grey shaded area marks the tentative [C II] 158 μm feature (top panel), and the location of the [O III] 88 μm line feature presented in Harikane et al. (2022).