Dense Cores in IRDC G14.225-0.506 revealed by ALMA Observations

Abstract: Dense cores in massive, parsec-scale molecular clumps are sites that harbor protocluster formation. We present results from observations towards a hub-filament structure of a massive Infrared Dark Cloud (IRDC) G14.225-0.506 using the Atacama Large Millimeter/submillimeter Array (ALMA). The dense cores are revealed by the 1.3 mm dust continuum emission at an angular resolution of $\sim$ 1.5'' and are identified through the hierarchical Dendrogram technique. Combining with the N$_2$D$^+$ 3-2 spectral line emission and gas temperatures derived from a previous NH$_3$ study, we analyze the thermodynamic properties of the dense cores. The results show transonic and supersonic-dominated turbulent motions. There is an inverse correlation between the virial parameter and the column density, which implies that denser regions may undergo stronger gravitational collapse. Molecular outflows are identified in the CO 2-1 and SiO 5-4 emission, indicating active protostellar activities in some cores. Besides these star formation signatures revealed by molecular outflows in the dense cores, previous studies in the infrared, X-ray, and radio wavelengths also found a rich and wide-spread population of young stellar objects (YSOs), showing active star formation both inside and outside of the dense cloud.