Three-dimensional dust geometry of the LMC HI ridge region as revealed by the IRSF/SIRIUS survey

We present a new method to evaluate the dust extinction (AV) along the line of sight using the InfraRed Survey Facility (IRSF) near-infrared (NIR) data of the Large Magellanic Cloud (LMC) HI ridge region. In our method, we estimate an AV value for each star from the NIR color excess and sort them from bluer to redder in each line of sight. Using the percentile values of the sorted AV, we newly construct the three-dimensional AV map. We compare the resultant AV map with the total hydrogen column density N(H) traced by velocity-resolved HI and CO observations. In the LMC HI ridge region, Fukui et al. (2017, PASJ, 69, L5) find two velocity components and an intermediate velocity one bridging them. Comparing our three-dimensional AV maps with N(H) maps at the different velocities, we find that the dust geometry is consistent with the scenario of the on-going gas collision between the two velocities as suggested in the previous study. In addition, we find difference by a factor of 2 in AV/N(H) between the two velocity components, which suggests that inflow gas from the Small Magellanic Clouds (SMC) is mixed in this region. As a whole, our results support the triggered star formation in 30 Doradus due to the large-scale gas collision caused by tidal interaction between the LMC and the SMC.

18 pages, 16 figures, accepted for publication in PASJ