GALACTIC-CENTER MOLECULAR ARMS, RING, AND EXPANDING SHELL .2. EXPANDING MOLECULAR SHELL

We consider the three-dimensional structure of the so-called 200-pc ex panding molecular ring in the Galactic Center by analyzing the (b, V-L SR) diagrams of the (CO)-C-13(J = 1-0) line emission from the Bell-Tel ephone-Laboratory survey. We show that the (b, V) features can be fitt ed by a spheroidal shell pinched at the equator (dumbbell-shaped shell ), which we call the expanding molecular shell (EMS). The radius is ab out 180 pc and the vertical extent is more than +/- 50 pc. The shell i s expanding at 160 km s(-1), and is rotating at 70 km s(-1). The assoc iation of the radio continuum emission indicates that the EMS is a mix ture of molecular and ionized hydrogen gases. An extended hot (X-ray) plasma appears to fill the interior of the shell, The estimated molecu lar mass of the shell is similar to 10(7) M. and its kinetic energy si milar to 2 x 10(54) erg.