Investigating embedded structures and gas kinematics in the infrared-dark cloud hosting bubble N59-North

Abstract

We present a multiwavelength study of an extended area hosting the bubble N59-North to explore the physical processes driving massive star formation (MSF). The Spitzer 8 mu m image reveals an elongated/filamentary infrared-dark cloud (length similar to 28 pc) associated with N59-North, which contains several protostars and seven ATLASGAL dust clumps at the same distance. The existence of this filament is confirmed through 13CO and NH3 molecular line data in a velocity range of [95, 106] km s-1. All dust clumps satisfy Kauffmann and Pillai's condition for MSF. Using Spitzer 8 mu m image, a new embedded hub-filament system candidate (C-HFS) is investigated toward the ATLASGAL clump, located near the filament's central region. MeerKAT 1.3 GHz continuum emission, detected for the first time toward C-HFS, reveals an ultracompact H ii region driven by a B2-type star, suggesting an early stage of HFS with minimal feedback from the young massive star. The comparison of the position-velocity (PV) and position-PV (PPV) diagrams with existing theoretical models suggests that rotation, central collapse, and end-dominated collapse are not responsible for the observed gas motion in the filament. The PPV diagram indicates the expansion of N59-North by revealing blueshifted and redshifted gas velocities at the edge of the bubble. Based on comparisons with magnetohydrodynamic simulations, this study suggests that cloud-cloud collision (CCC) led to the formation of the filament, likely giving it a conical structure with gas converging toward its central region, where C-HFS is located. Overall, the study supports multi-scale filamentary mass accretion for MSF, likely triggered by CCC.