* Astronomy

Blobrana · L

RE: TW Hydrae

Blobrana · L

Title: Kinematics of the CO Gas in the Inner Regions of the TW Hya Disk
Authors: Katherine A. Rosenfeld, Chunhua Qi, Sean M. Andrews, David J. Wilner, Stuartt A. Corder, C. P. Dullemond, Shin-Yi Lin, A. M. Hughes, Paola D'Alessio, P. T. P. Ho

We present a detailed analysis of the spatially and spectrally resolved 12CO J=2-1 and J=3-2 emission lines from the TW Hya circumstellar disk, based on science verification data from the Atacama Large Millimetre/Submillimetre Array (ALMA). These lines exhibit substantial emission in their high-velocity wings (with projected velocities out to 2.1 km/s, corresponding to intrinsic orbital velocities >20 km/s) that trace molecular gas as close as 2 AU from the central star. However, we are not able to reproduce the intensity of these wings and the general spatio-kinematic pattern of the lines with simple models for the disk structure and kinematics. Using three-dimensional non-local thermodynamic equilibrium molecular excitation and radiative transfer calculations, we construct some alternative models that successfully account for these features by modifying either (1) the temperature structure of the inner disk (inside the dust-depleted disk cavity; r < 4 AU); (2) the intrinsic (Keplerian) disk velocity field; or (3) the distribution of disk inclination angles (a warp). The latter approach is particularly compelling because a representative warped disk model qualitatively reproduces the observed azimuthal modulation of optical light scattered off the disk surface. In any model scenario, the ALMA data clearly require a substantial molecular gas reservoir located inside the region where dust optical depths are known to be substantially diminished in the TW Hya disk, in agreement with previous studies based on infrared spectroscopy. The results from these updated model prescriptions are discussed in terms of their potential physical origins, which might include dynamical perturbations from a low-mass companion with an orbital separation of a few AU.

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Blobrana · L

Title: Kinematics of Ionised Gas at 0.01 AU of TW Hya
Authors: M. Goto (1), A. Carmona (2), H. Linz (1), B. Stecklum (3), Th. Henning (1), G. Meeus (4), T. Usuda (5) ((1) MPIA, (2) University of Geneva, (3) Thüringer Landessternwarte Tautenburg, (4) Universidad Autónoma de Madrid, (5) Subaru Telescope)

We report two-dimensional spectroastrometry of Br gamma emission of TW Hya to study the kinematics of the ionised gas in the star-disk interface region. The spectroastrometry with the integral field spectrograph SINFONI at the Very Large Telescope is sensitive to the positional offset of the line emission down to the physical scale of the stellar diameter (~0.01 AU). The centroid of Br gamma emission is displaced to the north with respect to the central star at the blue side of the emission line, and to the south at the red side. The major axis of the centroid motion is P.A.= -20 degrees, which is nearly equal to the major axis of the protoplanetary disk projected on the sky, previously reported by CO sub millimetre spectroscopy (P.A.= -27 degrees) The line-of-sight motion of the Br gamma emission, in which the northern side of the disk is approaching toward us, is also consistent with the direction of the disk rotation known from the CO observation. The agreement implies that the kinematics of Br gamma emission is accounted for by the ionised gas in the inner edge of the disk. A simple modelling of the astrometry, however, indicates that the accretion inflow similarly well reproduces the centroid displacements of Br gamma, but only if the position angles of the centroid motion and the projected disk ellipse is a chance coincidence. No clear evidence of disk wind is found.

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