Formation of the Active Star-forming Region LHA 120-N 44 Triggered by Tidally Driven Colliding H i Flows

Abstract

Abstract The second most active site of high-mass star formation next to R136 in the Large Magellanic Cloud (LMC) is N44. We carried out a detailed analysis of H i at 60″ resolution by using the ATCA and Parkes data. We presented decomposition of the H i emission into two velocity components (the L and D components) with a velocity separation of ∼60 km s−1. In addition, we newly defined the I component whose velocity is intermediate between the L and D components. The D component was used to derive the rotation curve of the LMC disk, which is consistent with the stellar rotation curve. Toward the active cluster-forming region of LHA 120-N 44, the three velocity components of H i gas show signatures of dynamical interaction, including bridges and complementary spatial distributions. We hypothesize that the L and D components have been colliding with each other since 5 Myr ago, and the interaction triggered formation of the O and early-B stars ionizing N44. In the hypothesis, the I component is interpreted as decelerated gas in terms of momentum exchange in the collisional interaction of the L and D components. In the N44 region, the Planck submillimeter dust optical depth is correlated with the H i intensity, which is well approximated by a linear regression. We found that the N44 region shows a significantly steeper regression line than in the bar region, indicating less dust abundance in the N44 region, which is ascribed to the tidal interaction between the LMC and the SMC 0.2 Gyr ago.