New evidences in IRDC G333.73 + 0.37: colliding filamentary clouds, hub-filament system, and embedded cores

Abstract

ABSTRACT To unravel the star formation process, we present a multi-scale and multi-wavelength study of the filamentary infrared dark cloud (IRDC) G333.73 + 0.37, which hosts previously known two H ii regions located at its center. Each H ii region is associated with a mid-infrared source, and is excited by a massive OB star. Two filamentary structures and a hub-filament system (HFS) associated with one H ii region are investigated in absorption using the Spitzer 8.0 μm image. The 13CO(J = 2–1) and C18O(J = 2–1) line data reveal two velocity components (around −35.5 and −33.5 km s−1) toward the IRDC, favouring the presence of two filamentary clouds at different velocities. Non-thermal (or turbulent) motions are depicted in the IRDC using the C18O line data. The spatial distribution of young stellar objects (YSOs) identified using the VVV near-infrared data traces star formation activities in the IRDC. Low-mass cores are identified toward both the H ii regions using the ALMA 1.38 mm continuum map. The VLT/NACO adaptive-optics L′-band images show the presence of at least three point-like sources and the absence of small-scale features in the inner 4000 AU around YSOs NIR31 and MIR 16 located toward the H ii regions. The H ii regions and groups of YSO are observed toward the central part of the IRDC, where the two filamentary clouds intersect. A scenario of cloud–cloud collision or converging flows in the IRDC seems to be applicable, which may explain star formation activities including HFS and massive stars.