Predicted rotation signatures in MHD disc winds and comparison to DG Tau observations.

Nicholas Pesenti (1) , Catherine Dougados (1) , Sylvie Cabrit (2) , Jonathan Ferreira (1) , Fabien Casse (3) , Paulo García (4) , Darren M. O'Brien (4)

1 LAOG - Laboratoire d'Astrophysique de Grenoble
2 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
3 Institute for Plasma Physics Rijnhuizen, FOM
4 Universidade do Porto = University of Porto

Motivated by the first detections of rotation signatures in the DG Tau jet (Bacciotti et al. \cite{bacciotti2002}), 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 ( 50) are ruled out for the medium-velocity component in the DG Tau jet.

Domaines: Astrophysique [astro-ph]; Planète et Univers [physics]

Nicholas Pesenti, Catherine Dougados, Sylvie Cabrit, Jonathan Ferreira, Fabien Casse, et al.. Predicted rotation signatures in MHD disc winds and comparison to DG Tau observations.. Astronomy and Astrophysics - A&A, 2004, 416, pp.L9-L12. ⟨10.1051/0004-6361:20040033⟩. ⟨hal-03733351⟩