Morphology and Collimation Scales

The pioneering work of [24] using long-slit spectroscopy with accurate central continuum subtraction has revealed spatial extensions of a few arcsec-onds in the forbidden emission line regions of a dozen CTTs. Conventional narrow-band imaging with the HST has provided the first images of jets from 2 CTTs [39], HH 30, and HL Tau. Observations with the PUE'O AO bonnette on the 4 m CFH telescope, used both in conventional narrow-band imaging and in combination with the OASIS IFS, has provided remarkable 0".2-0".4 resolution images of the small-scale jets from DG Tau (Fig. 3), CW Tau, and RW Aur on scales <4"[13, 28, 29]. Very high angular resolution images (0".1) reconstructed from stepped long-slit and slitless spectroscopy with STIS on the HST have also been obtained for the DG Tau, RW Aur [4, 45], CW Tau, UZ Tau E, and HN Tau microjets [21].

These observations reveal a complex morphology for the jet emission close to the central source (Fig. 3). The jet brightness distribution is dominated by knots with separations of order 1". A clear bow-shaped structure is detected in the DG Tau microjet outer knot, suggesting that shocks may play an important role in the line excitation process. T Tauri microjets thus appear as a scaled down version of the Herbig-Haro flows from younger sources, an indication that the same ejection mechanism is at work through the star formation phases.

Figure 4 shows the variation of jet width against projected distance from the source for a number of CTTs outflows, combining high-angular resolu-

Fig. 3. [O i] image of the DG Tau A microjet obtained with PUE'O on the CFHT. PSF FWHM = 0." .2 after OA correction. After deconvolution final angular resolution of 0.1". Adapted from [14]
0 0

Post a comment