We present interferometric maps of the RW Aur system obtained with the IRAM Plateau de Bure Interferometer in CO(J = 2−1), CO(J = 1−0), and nearby continuum. The sub-arcsecond angular resolution (0.89 × 0.58 ) and high-sensitivity reached at 1.3 mm enable us to resolve three molecular structures: (1) an optically thick disk around RW Aur A in rotation about the optical jet axis, (2) a disturbed asymmetric peak around RW Aur B, (3) a 600 AU-long "arm" of material trailing from the RW Aur A disk. Comparison with Keplerian models indicates that the RW Aur A disk is the smallest detected so far around a T Tauri star (radius 40−57 AU) and that the CO emitting layer at the outer edge is warmer than the dust (T out 60−100 K) and relatively thick (N warm 0.1−10 × 10 22 cm −2 ). The morphology and kinematics of the detected features strongly suggest that we are witnessing tidal stripping of the primary disk by the recent fly-by of RW Aur B. We speculate that tidal dissipation might explain the warmer gas temperatures in the RW Aur A disk compared with typical T Tauri stars, and perhaps play a role in its elevated accretion rate. We also find that the rotation sense of the RW Aur A disk is opposite to transverse velocity shifts in the optical jet reported by Woitas et al. (2005, A&A, 432, 149). We argue that these transverse shifts are likely to represent only upper limits to the true jet rotation speed. The limits remain consistent with current models of MHD launching from the disk.

Abstract.Motivated by the first detections of rotation signatures in the DG Tau jet , we examine possible biases affecting the relation between detected rotation signatures and true azimuthal velocity for self-similar MHD disc winds, taking into account projection, convolution as well as excitation gradients effects. We find that computed velocity shifts are systematically smaller than the true underlying rotation curve. When outer slower streamlines dominate the emission, we predict observed shifts increasing with transverse distance to the jet axis, opposite to the true rotation profile. Determination of the full transverse rotation profile thus requires high angular resolution observations (<5 AU) on an object with dominant inner faster streamlines. Comparison of our predictions with HST/STIS observations of DG Tau clearly shows that self-similar, warm MHD disc wind models with λ = 13 and an outer radius of the disc 3 AU are able to reproduce detected velocity shifts, while cold disc wind models (λ > 50) are ruled out for the medium-velocity component in the DG Tau jet.

Abstract.We investigate the emissivity properties of the main near-IR transitions of the Fe + ion in the conditions prevailing in the inner regions of jets from young stars, based on a simplified 16-level atom model. We present new diagnostic diagrams involving prominent near-IR line ratios that allow us to constrain the electronic density, temperature, and Fe gas phase abundance ratio, independently of the heating process. Comparison with recent near-IR observations of a sample of HH objects indicates gas phase Fe abundances ranging from 15-50% up to 100% of the solar value (depending on the assumed temperature and on the HH object), in agreement with the moderate depletions previously derived from optical line ratios or shock models. Hence, it appears that Fe-bearing dust is efficiently destroyed in stellar jets. We then use our Fe cold disk wind model reproduces quite well the two velocity components observed at −100 and −300 km s −1 , although the high velocity component appears overestimated by a factor of 1.5 in the DG Tau jet. However, the model predicts too little emission at intermediate velocities and insufficient densities. Similar problems were encountered in previous model comparisons in the optical range with jets from T Tauri stars. Denser disk winds with stronger heating at the jet base, which have been invoked for optical jets, also appear needed in younger, embedded Class I jet sources.

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