2002/06/11 by F. Bacciotti, Francesca Bacciotti, T. P. Ray +7 · 267 citations
Physics and Astronomy · #Angular momentum #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Doppler effect #Jet (fluid) #Line (geometry) #Outflow #Rotation (mathematics) #Solar and Space Plasma Dynamics #Spectral line #Spectroscopy #Transverse plane #astro-ph
paper · pdf · doi:10.1086/341725
published in The Astrophysical Journal 576(1), 222-231 (IOP Publishing) · aastex, 23 pages, 5 b/w figures, 3 color figures, ApJ in press
arxiv created 2002/06/11 · openalex publication_date 2002/09/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We have carried out a kinematical, high angular resolution (~0 1) study of the optical blueshifted flow from DG Tau within 0 5 from the source (i.e., 110 AU when deprojected along this flow). We analyzed optical emission line profiles extracted from a set of seven long-slit spectra taken with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope , obtained by maintaining the slit parallel to the outflow axis while at the same time moving it transversely in steps of 0 07. For the spatially resolved flow of moderate velocity (peaking at -70 km s -1 ), we have found systematic differences in the radial velocities of lines from opposing slit positions, i.e., on alternate sides of the jet axis. The results, obtained using two independent techniques, are corrected for the spurious wavelength shift due to the uneven illumination of the STIS slit. Other instrumental effects are shown to be either absent or unimportant. The derived relative Doppler shifts range from 5 to 20 km s -1 . Assuming that the flow is axially symmetric, the velocity shifts are consistent with the southeastern side of the flow moving toward the observer faster than the corresponding northwestern side. If this finding is interpreted as rotation, the flow is then rotating clockwise looking from the jet toward the source and the derived toroidal velocities are in the range 6-15 km s -1 , depending on position. Combining these values with recent estimates of the mass-loss rate, one would obtain an angular momentum flux, for the low- to moderate-velocity regime of the flow, of w , lm ~ 3.8 × 10 -5 M ☉ yr -1 AU km s -1 . Our findings may constitute the first detection of rotation in the initial channel of a jet flow. The derived values appear to be consistent with the predictions of popular magnetocentrifugal jet-launching models, although we cannot exclude the possibility that the observed velocity differences are due to some transverse outflow asymmetry other than rotation.