Molecular Cloud Cores in the Galactic Center 50 $\rm km~s^{-1}$ Molecular Cloud

Abstract

The Galactic Center 50 km s$^{-1}$ Molecular Cloud (50MC) is the most remarkable molecular cloud in the Sagittarius A region. This cloud is a candidate for the massive star formation induced by cloud-cloud collision (CCC) with a collision velocity of $\sim30\rm~km~s^{-1}$ that is estimated from the velocity dispersion. We observed the whole of the 50MC with a high angular resolution ($\sim2.0''\times1.4''$) in ALMA cycle 1 in the H$^{13}$CO$^+~J=1-0$ and ${\rm C^{34}S}~J=2-1$ emission lines. We identified 241 and 129 bound cores with a virial parameter of less than 2, which are thought to be gravitationally bound, in the H$^{13}$CO$^+$ and ${\rm C^{34}S}$ maps using the clumpfind algorithm, respectively. In the CCC region, the bound ${\rm H^{13}CO^+}$ and ${\rm C^{34}S}$ cores are 119 and 82, whose masses are $68~\%$ and $76~\%$ of those in the whole 50MC, respectively. The distribution of the core number and column densities in the CCC are biased to larger densities than those in the non-CCC region. The distributions indicate that the CCC compresses the molecular gas and increases the number of the dense bound cores. Additionally, the massive bound cores with masses of $>3000~M_{\odot}$ exist only in the CCC region, although the slope of the core mass function (CMF) in the CCC region is not different from that in the non-CCC region. We conclude that the compression by the CCC efficiently formed massive bound cores even if the slope of the CMF is not changed so much by the CCC.