Statistical Properties of Molecular Clumps in the Galactic Center 50 km s-1 Molecular Cloud

Abstract

Abstract We present the statistical properties of molecular clumps in the Galactic center 50 km s$ ^{-1}$ molecular cloud (GCM-0.02-0.07) based on observations of the CS $ J$$ =$ 1–0 emission line with the Nobeyama Millimeter Array. In the cloud, 37 molecular clumps with local thermodynamic equilibrium (LTE) masses of 2 $ \times$ 10$ ^{2}$ –6 $ \times$ 10$ ^{3}\ M_{\odot}$ were identified by using the clumpfind algorithm. The velocity widths of the molecular clumps are about five-fold those of Galactic disk molecular clouds with the same radius. The virial-theorem masses are three-fold the LTE masses. The mass and size spectra can be described by power laws of $ dN/dM$$ \propto$$ M^{-2.6\pm0.1}$ ($ M$$ \gtrsim$ 900 $ M_{\odot}$ ) and $ dN/dR$$ \propto$$ R^{-5.9\pm0.3}$ ($ R$$ \gtrsim$ 0.35 pc), respectively. The statistical properties of the region interacting with the Sgr A East shell and those of the non-interacting part of the cloud are significantly different. The interaction probably makes the mass function steeper, from $ dN/dM$$ \propto$$ M^{-2.0\pm0.1}$ in the non-interacting part to $ dN/dM$$ \propto$$ M^{-4.0\pm0.2}$ in the interacting region. On the other hand, the interaction presumably truncates the size spectrum on the larger side of $ R$$ \sim$ 0.4 pc.