High-Resolution Studies of the Dense Molecular Cores toward Massive Star-Forming Regions

Abstract

We present the results of the imaging of dense molecular cores in three massive star-forming regions (IRAS 02461$+$6147, IRAS 03035$+$5819, and IRAS 06058$+$2138), which are associated with luminous infrared sources with $1 \hbox{--} 5 \times 10^{4} \,{{{L}_{\odot}}}$. The C${{18\atop} \mathrm{O}}$ ($J = 1 \hbox{--} 0$) molecular emission from the dense cores and the thermal dust and/or free-free emission at 98 GHz and 110 GHz in the hot core candidates have been imaged with a resolution of $\sim {4{}^{\mathrm {\prime \prime }}}$ using the Nobeyama Millimeter Array. We identified 28 C${{18\atop} \mathrm{O}}$ dense cores, whose mass, effective radius, and line-width range from 2.1 to 29${M}_{\odot}$, from 0.013 to 0.108 pc, and from 0.7 to $2.7 \,\mathrm{km} \,\mathrm{s}^{-1}$, respectively, and identified four thermal dust millimeter continuum sources (MCSs). We divided the C${{18\atop} \mathrm{O}}$ cores into two types, a turbulent core and a non-turbulent core. The non-turbulent cores are similar to the typical cores in the low-mass star-forming regions. The turbulent cores have a higher average $\mathrm{H}_2$ density than those of the non-turbulent cores, and the external pressure of these cores is 100–1000 times higher than that of low-mass star-forming regions. Three of the turbulent cores are associated with massive protostar candidates and the intensity peak of MCS. Massive stars are formed from the turbulent cores which are gravitationally bound. In order to form such a turbulent core a molecular cloud has a large kinetic motion and a large mass.