Position-velocity diagrams along the plane of the disk of ¹²CO(2–1), ¹³CO(1–0), HCO⁺ (1–0), and HCO⁺ (3–2). Contours start at 3σ. Except for HCO⁺ (3–2), the envelope-dominated central velocity channels were masked out for the analysis (see also Figs. A.1, A.4 and A.5). Overlaid as red contours for comparison (with the y-axis being ∆y instead of υ_LSR) is the 230 GHz dust continuum emission from the disk (2.5, 7.5, and 15 mJy beam⁻¹), rotated by 32°. Green lines show the Keplerian rotation curve for a central mass of 0.55 M_⊙ and systemic velocity of υ₀ = 5.95 km s⁻¹ (only to guide the eye; this is not the fit to the data).