Typical CO(2–1) (a and b) and SiO(5–4) (c and d) lines toward molecular outflows, here that of core #8. (a, c): lines averaged over the complete extent of the outflow, thus including both the blue and red lobes. (b, d): lines averaged over one high-velocity knot, here knot R2 of core #8. Line absorption around the velocity at rest, indicated by a dashed line, is due to missing short spacings and optical thickness. The transition between the low- and high-velocity components of the molecular outflows is indicated in panels b and d with a blue dotted line.