Active star formation across the whole Large Magellanic Cloud triggered by tidally-driven colliding HI flows

Abstract: The galactic tidal interaction is a possible mechanism to trigger the active star formation in galaxies. Recent analyses using the Hi data in the Large Magellanic Cloud (LMC) proposed that the tidally driven colliding HI flows, induced by the galactic interaction with the Small Magellanic Cloud (SMC), triggered high-mass star formation in the southeastern HI Ridge, including R136 and $\sim$400 O/WR stars, and the galactic center region hosting the N44 region. This study performed a comprehensive HI data analysis across the LMC and found that two Hi velocity components defined in the early studies (L- and D- components) are quasi-ubiquitous with signatures of interaction dynamically toward the other prominent HII regions, such as N11 and N79. We characterize the intimidate velocity range (I-component) between the two components as the decelerated gas by momentum conservation in the collisional interaction. The spatial distributions of the I-component and those of the O/WR stars have good agreements with each other whose fraction is more than $\sim$70% at a scale of $\sim$15 pc, which is significantly smaller than the typical GMC size. Based on the results of our new simulations of the LMC-SMC interaction, we propose that the interaction about 0.2 Gyr ago induced efficient infall of gas from the SMC to the LMC and consequently ended up with recent formation of high-mass stars due to collisions of HI gas in the LMC. The new numerical simulations of the gas dynamics successfully reproduce the current distribution of the L-component. This lends theoretical support for the present picture.