2024MNRAS.535..107K

We present 850 $\mu$m polarized observations of the molecular cloud G34.26 + 0.15 taken using the POL-2 polarimeter mounted on the James Clerk Maxwell Telescope (JCMT). G34.26 + 0.15 is a hub-filament system with ongoing high-mass star formation, containing multiple H II regions. We extend the histogram of relative orientations technique with an alternative application that considers the alignment of the magnetic field to the filaments and a H II region boundary, denoted as the filament alignment factor ($\xi _{F}$) and the ellipse alignment factor ($\xi _{E}$), respectively. Using these metrics, we find that, although in general the magnetic field aligns parallel to the filamentary structure within the system in the north-west, the magnetic field structure of G34.26 + 0.15 has been radically reshaped by the expansion of an evolved H II region in the south-east, which itself may have triggered further high-mass star formation in the cloud. Thus, we suggest high-mass star formation is occurring through both mass accretion as per the hub-filament model from one side and compression of gas under stellar feedback from the other. We also use HARP (Heterodyne Array Receiver Program) observations of C$^{18}$O from the CHIMPS survey to estimate the magnetic field strength across the cloud, finding strengths of $\sim$0.5-1.4 mG.