Statistical Properties of Molecular Clumps in the Galactic Center 50 km s$^{-1}$ Molecular Cloud

TL;DR

This study analyzes the statistical properties of molecular clumps in the Galactic center's 50 km s$^{-1}$ molecular cloud using CS emission data, revealing differences in mass and size distributions due to interactions with Sgr A East.

Contribution

It provides detailed statistical analysis of molecular clumps in the Galactic center, highlighting the impact of environmental interactions on their properties.

Findings

Clumps have velocity widths five times larger than disk clouds.

Mass and size spectra follow power laws with specific indices.

Interactions steepen the mass function and truncate the size spectrum.

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 thermal equilibrium (LTE) masses of $2\times10^2-6\times10^3 M_\odot$ were identified by using the {\it 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 $dN/dM\propto M^{-2.6\pm0.1}$ ($M\gtrsim 900M_\odot$) 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.