SMA studies of highly collimated jets from very young protostars have produced many stunning images (Figure 2). These have placed very strong limits on any jet rotation, tightly constraining the size of the jet-launching radius and thus testing directly the disk wind and X-wind theories of outflow generation (Lee et al. 2006; 2007; 2009). While the observations cannot completely rule out the disk wind model they do strongly support the X-wind model. The SMA has made the first discoveries of low-mass, low-velocity molecular outflows from young brown dwarfs and candidate proto-brown dwarfs (Bourke et al. 2005; Phan-Bao et al. 2008) (Figure 3). With single dish telescopes it is not possible to identify such flows in the presence of widespread CO cloud emission, due to their small size and small velocity range. The SMA has also enabled the driving source(s) of many larger scale outflows to be identified in regions containing multiple sources (Yeh et al. 2007; Chen et al. 2008).

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Figure 2: The highly collimated jet from the protostar HH 211-mm, imaged with the SMA with sub-arcsecond resolution. (a) The grayscale image is near-infrared emission from Hirano et al. (2006). The cross marks the position of HH211-mm. (b)-(d) 352 GHz continuum contours are shown in green, and the jet emission as traced by SiO J = 8-7 emission is shown as red and blue contours for red-shifted and blue-shifted emission, respectively (Lee et al. 2009).

A recent, and potentially very important, discovery is that of a candidate "first hydrostatic core" (Chen et al. 2010). This is a phase in star formation between that of a starless, dense core on the verge of collapse and a full fledged protostar. It is expected that this is a very short-lived phase, and observations at far-infrared and submillimeter wavelengths are the only way to identify it. Chen et al., using the SMA, identified a CO outflow and weak, compact continuum emission from the center of a dense core that contains no near- or mid-infrared point source (as would be expected from a bona fide protostar). If confirmed, this will be a major discovery in star formation, and stellar evolution in general.

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Figure 3: The compact low-mass outflow from L1014-IRS, as discovered using the SMA. Top: A near-infrared image of the region around L1014-IRS (courtesy Tracy Huard). L1014-IRS is located near the middle in the green box, and a conical shaped nebula is seen directed upwards from its location, strongly suggesting the presence of an outflow. Bottom: A zoomed in section of the infrared image (in grayscale), overlaid with blue and red contours showing high velocity emission from CO J=2-1 due to outflow gas in bipolar outflow, one of the key signatures of star formation. In this panel, the white cross indicates the position of L1014-IRS. This is one of the smallest and least-massive molecular outflows known (Adapted from Bourke et al. 2005).

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