2012ApJ...756...87M

This paper reports the discovery of a helical molecular cloud in the central molecular zone (CMZ) of our Galaxy. This "pigtail" molecular cloud appears at (l, b, V_LSR) ≃ (-0°.7, + 0°.0, - 70 to -30 km/s), with a spatial size of ∼20x20 pc² and a mass of (2-6)x10⁵ M_☉. This is the third helical gaseous nebula found in the Galactic center region to date. Line intensity ratios indicate that the pigtail molecular cloud has slightly higher temperature and/or density than the other normal clouds in the CMZ. We also found a high-velocity wing emission near the footpoint of this cloud. We propose a formation model of the pigtail molecular cloud. It might be associated with a magnetic tube that is twisted and coiled because of the interaction between clouds in the innermost x₁ orbit and ones in the outermost x₂orbit.