Probing the Gaseous Disk of T Tau N with CN 5-4 Lines
Woitke, P.; Kamp, I.; White, G. J.; Podio, L.; Codella, C.; Dougados, C.; Spaans, M.; Sandell, G.; Aresu, G.; Brittain, S.; Nisini, B.; Meijerink, R.; Grady, C.; Cabrit, S.; Thi, W. -F.
Italy, France, Netherlands, United States, Chile, United Kingdom
Abstract
We present spectrally resolved observations of the young multiple system T Tau in atomic and molecular lines obtained with the Heterodyne Instrument for the Far Infrared on board Herschel. While CO, H2O, [C II], and SO lines trace the envelope and the outflowing gas up to velocities of 33 km s-1 with respect to systemic, the CN 5-4 hyperfine structure lines at 566.7, 566.9 GHz show a narrow double-peaked profile centered at systemic velocity, consistent with an origin in the outer region of the compact disk of T Tau N. Disk modeling of the T Tau N disk with the thermo-chemical code ProDiMo produces CN line fluxes and profiles consistent with the observed ones and constrain the size of the gaseous disk (R_out=110^{+10}_{-20} AU) and its inclination (i = 25°± 5°). The model indicates that the CN lines originate in a disk upper layer at 40-110 AU from the star, which is irradiated by the stellar UV field and heated up to temperatures of 50-700 K. With respect to previously observed CN 2-1 millimeter lines, the CN 5-4 lines appear to be less affected by envelope emission, due to their larger critical density and excitation temperature. Hence, high-J CN lines are a unique confusion-free tracer of embedded disks, such as the disk of T Tau N.