Signs of Dynamic Gas Inflow toward Intermediate-mass Cores Embedded in IRDC

ABSTRACT :
The study of gas dynamics is key to understanding how star formation occurs, especially in high-mass star-forming regions. Recent high-resolution observations of infrared dark clouds (IRDCs), the birthplaces of high-mass stars, imply the necessity of core growth through gas feeding. To investigate the prevalence of the high-mass infall rate, we performed ALMA observations of twelve 70 µm dark high-mass clumps that are parts of IRDCs. Here we focus on a case study of AGAL337.541-00.082, a massive (1180 Msun), dense (0.45 g/cm2), and cold (12 K) region. Previously classified as a high-mass prestellar clump, recent observations show two intermediate-mass cores associated with east-west CO outflows at the clump center. Analysis of the N2H+ (J=1-0) shows the red-shifted and blue-shifted components north and south of the two cores, respectively. The position-velocity diagram represents the connection of these components at the core positions, implying gas inflows towards two cores at a high mass inflow rate (>10^-4 Msun/yr). In addition, at the core scale we detect infall signatures from HNC (J=3-2), also implying a high infall rate (~10^-3 Msun/yr). The detection of such a high infall/inflow rate in IRDCs implies the role of gas feeding the embedded cores to form high-mass stars.