title: The $^{12}$CO ($J=1-0$) emission from the protoplanetary disk around CW Tau 

authors: Yusuke Aso, Masahiko Hayashi, Takashi Tukagoshi, Shin Koyamatsu (The University of Tokyo), Ryohei Kawabe, Masao Saito, Kazuya Saigo (NAOJ), Yoshimi Kitamura (JAXA)

abstract: 
We report the detection of $^{12}$CO ($J=1-0$) emission from the protoplanetary disk around CW~Tau.
Detecting millimeter-wave emission lines from classical T~Tauri stars is generally difficult because they are, in almost all cases with few exceptions such as DM~Tau or GG~Tau, associated with strong ambient (background/foreground) gas emission overlapping stellar systemic velocities.
With the Nobeyama Millimeter Array (beam size\,$\sim$\,3$''$), we detected a broad $^{12}$CO line over the velocity from $V_{\rm LSR}$\,=\,4 to 8\,km\,s$^{-1}$ with the emission at 6--7\,km\,s$^{-1}$ resolved out due to the ambient component.
Examination of the kinematics of CO gas revealed that the emission peaks lie at $\sim$\,2$''$ NE of CW~Tau at $\sim$\,1\,km\,s$^{-1}$ blueshifted channels and at $\sim$\,1$''$ SW at a $\sim$\,1.5\,km\,s$^{-1}$ redshifted channel, with higher velocity emission peaks coinciding with the stellar position.
Because the velocity gradient is perpendicular to the direction of the optical  jet from CW~Tau, we conclude that the CO emission arises from a differentially rotating gas disk around the star.
The observed velocity field is consistent with a Keplerian rotating disk around a 1.4\,$M_\odot$ star with an inclination angle of $30^\circ\pm 10^\circ$ (0$^\circ$=face-on).