HCO+ emission in the HH7-11 region: the slowest component of the outflow?

Results of mapping of the region of high-velocity outflow in HH7-11 in the J = 4-3 transition of HCO(+) are compared with published optical, CO, and J = 1-0 HCO(+) maps are presented. Unlike the latter interferometric data, a bright compact source associated with the exciting star, plus weaker emission throughout the region, is observed. Extended emission surrounds the line of HH objects, and has a structure very similar to that of the blueshifted CO outflow. Spectra of the J = 4-3 and 3-2 lines in selected positions within the flow region indicate two physical components: cool gas at a density of a few million per cu cm at the velocity of SSV13 and the ambient cloud, and warm (35 K) gas at a few hundred thousand per cu cm blueshifted by about 1 km/s. The close agreement between the HCO(+) and higher velocity CO suggests that the former arises from the densest, slowest component of the molecular flow. The structure appears to favor a confined jet rather than a shocked cloudlet model.