T. Handa et al., DETECTION OF A CIRCUMSTELLAR GAS AROUND DM-TAURI - A PROTOPLANETARY DISK AROUND A SINGLE STAR, The Astrophysical journal, 449(2), 1995, pp. 894-899
Sensitive molecular line observations carried out with the Nobeyama 45
m telescope have resulted in the detection of the (CO)-C-12 (d = 1-0)
and (CO)-C-13 (J = 1-0) emission centered on the young classical T Ta
uri star, DM Tau. The derived peak antenna temperatures are 0.3 K in (
CO)-C-12 and 0.1 K in (CO)-C-13. NO (CO)-O-18 emission was detected at
an upper limit (3 a) of 45 mK. The emission feature has a line width
of 1.7 km s(-1) and is centered at upsilon(LSR) = 5.9 km s(-1), which
coincides well with the reported radial velocity for DM Tau (5.9 +/- 2
.1 km s(-1)). The (CO)-C-13 profile shows a symmetric double peak, sug
gesting a Keplerian rotating disk. These observations suggest that the
molecular gas is associated with and is most probably gravitationally
bound to DM Tau. The derived radius of the gaseous disk is about 1000
AU using an optically thick disk model and a Keplerian rotating disk
model. The gaseous mass is between 7 x 10(-4) and 1 x 10(-3) M. from t
he (CO)-C-13 intensity and the upper limit of (CO)-O-18 intensity. Our
results suggest that molecular gas is depleted from the standard gas-
to-dust mass ratio or that mass distribution in the disk is steeper th
an the standard law, r(-1.5), although our observations cannot detect
emission from an optically thick gaseous component inward of r < 100 A
U, if the emission comes from a Keplerian rotating disk.