2014ApJ...783...62T

We report the detection of extremely broad emission toward two molecular clumps in the Galactic central molecular zone. We have mapped the Sagittarius C complex (-0.°61 < l < -0.°27, -0.°29 < b < 0.°04) in the HCN J = 4-3, ¹³CO J = 3-2, and H¹³CN J = 1-0 lines with the ASTE 10 m and NRO 45 m telescopes, detecting bright emission with 80-120 km/s velocity width (in full-width at zero intensity) toward CO-0.30-0.07 and CO-0.40-0.22, which are high velocity compact clouds (HVCCs) identified with our previous CO J = 3-2 survey. Our data reveal an interesting internal structure of CO-0.30-0.07 comprising a pair of high velocity lobes. The spatial-velocity structure of CO-0.40-0.22 can be also understood as a multiple velocity component, or a velocity gradient across the cloud. They are both located on the rims of two molecular shells of about 10 pc in radius. Kinetic energies of CO-0.30-0.07 and CO-0.40-0.22 are (0.8-2)x10⁴⁹ erg and (1-4)x10⁴⁹ erg, respectively. We propose several interpretations of their broad emission: collision between clouds associated with the shells, bipolar outflow, expansion driven by supernovae (SNe), and rotation around a dark massive object. These scenarios cannot be discriminated because of the insufficient angular resolution of our data, though the absence of a visible energy source associated with the HVCCs seems to favor the cloud-cloud collision scenario. Kinetic energies of the two molecular shells are 1x10⁵¹ erg and 0.7x10⁵¹ erg, which can be furnished by multiple SN or hypernova explosions in 2x10⁵ yr. These shells are candidates of molecular superbubbles created after past active star formation.