tokens: G327.29-0.5 – show shallow blue absorption wings that are not reproduced by the fits because no outflow component is included in the model. Nevertheless, the fit methods allow us to reliably adjust the free-fall fraction even in these cases. 4.4. Simultaneous HCO<inline-formula specific-use="simple-math"><sup>+</sup></inline-formula> modeling Even more indications of an additional outflow component are seen in most HCO lines. The dotted fits to the HCO lines in Fig. 6 show the infall models with only an adjustment of the HCO abundance. In general, they cannot reproduce the observed profile signatures, that is, the broad emission, the deep self-absorption, and the relative intensities of the blue and red peaks. We therefore added outflow emission to the RATRAN models of HCO in the center plane of the envelope before the ray-tracing step, as was done in Mottram et al. (2013) . Examples of profiles that can be fit satisfyingly with this additional component are G34.26+0.1 and G35.20-0.7, as shown in Fig. 6 . The outflow components have typical widths of 10 km s and are in some cases slightly shifted from the systemic velocities to account for the asymmetry of the outflow lobes. For several clumps, the HCO abundances are relatively small but consistent with typical depletion factors found in Giannetti et al. (2014) . Still, several HCO profiles cannot be reproduced with the simplicity of the spherical models, pointing to inherent difficulties in the interpretation of HCO profiles as an infall indicator. Fig. 6 Comparison of APEX HCO (4–3) observations with the SOFIA ammonia absorption in sources showing redshifted absorption. We show the RATRAN modeling result of HCO (4–3) in red using variable abundances with and without (dotted) additional outflow components. 5. Discussion and conclusions Adding the results from Wyrowski et al. (2012) , eight out of eleven massive clumps have been found with redshifted absorption that is indicative of infall motions. This fraction of 72% is substantially higher than found in past searches for the blue-skewed profile signature, see, for example, Fuller et al. (2005) , Wu et al. (2007) , López-Sepulcre et al. (2010) , Reiter et al. (2011) and Rygl et al. (2013) . From our comparison of ammonia absorption with line profiles of dense gas tracers lines, we conclude that outflows are the most likely reason for hiding infall motions in the clump envelopes. This effect is less prominent in the THz ammonia spectra. While we see the red lobe due to the high excitation even in emission in the extreme outflow source G5.89-0.4, other sources are, if at all, only affected by blueshifted absorption from the outflow in front of the continuum. These absorption wings are similar to the blue emission wings in the CS (7–6) spectra, but do not affect the measurements of the main redshifted absorption from the envelope. The excitation in most outflows is too low to excite the high critical density THz ammonia line (), but are high
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