shape, but is not that highly collimated, whilst the redshifted lobe is severely affected by self absorption. If these type of outflows are driven by jets then we should see the shock-excited emission lines characteristic of low-mass objects. However, ground-based searches for molecular hydrogen emission at 2$\mu$m have often turned up very little to support this picture (Davis et al. 1998), although see Davis et al. (2004). Optical searches for shocked emission in the outer reaches of molecular clouds where the flows terminate and extinction is expected to be less have also not detected anything significant (Alvarez & Hoare 2005). Images from the SPITZER satellite in the 4.5$\mu$m filter are turning up numerous examples of outflow lobe emission, most likely from rotational lines of molecular hydrogen (Noriega-Crespo et al. 2004). This band occurs close to where there is a minimum in the extinction curve (Indebetouw et al. 2005) and should be a useful probe of massive outflows.

![OVRO map of the bipolar molecular outflow from S140 IRS 1. The $^{12}$CO 1-0 observation has a resolution of about 4 whilst the 2.7 mm continuum emission showing the two point sources was made at a resolution of 2. From Gibb, Hoare & 