The Infrared Dark Cloud ( IRDC ) G028.23-00.19 hosts a massive ( 1,500 M _ { \odot } ) , cold ( 12 K ) , and 3.6-70 \mu m IR dark clump ( MM1 ) that has the potential to form high-mass stars .
We observed this prestellar clump candidate with the SMA ( \sim 3 \farcs 5 resolution ) and JVLA ( \sim 2 \farcs 1 resolution ) in order to characterize the early stages of high-mass star formation and to constrain theoretical models .
Dust emission at 1.3 mm wavelength reveals 5 cores with masses \leq 15 M _ { \odot } .
None of the cores currently have the mass reservoir to form a high-mass star in the prestellar phase .
If the MM1 clump will ultimately form high-mass stars , its embedded cores must gather a significant amount of additional mass over time .
No molecular outflows are detected in the CO ( 2-1 ) and SiO ( 5-4 ) transitions , suggesting that the SMA cores are starless .
By using the NH _ { 3 } ( 1,1 ) line , the velocity dispersion of the gas is determined to be transonic or mildly supersonic ( \Delta V _ { nt } / \Delta V _ { th } \sim 1.1-1.8 ) .
The cores are not highly supersonic as some theories of high-mass star formation predict .
The embedded cores are 4 to 7 times more massive than the clump thermal Jeans mass and the most massive core ( SMA1 ) is 9 times less massive than the clump turbulent Jeans mass .
These values indicate that neither thermal pressure nor turbulent pressure dominates the fragmentation of MM1 .
The low virial parameters of the cores ( 0.1-0.5 ) suggest that they are not in virial equilibrium , unless strong magnetic fields of \sim 1-2 mG are present .
We discuss high-mass star formation scenarios in a context based on IRDC G028.23-00.19 , a study case believed to represent the initial fragmentation of molecular clouds that will form high-mass stars .