2025-05-30 –, Main Conference Room
The formation of massive star clusters containing massive stars is thought to require some kind of triggering. The Large Magellanic Cloud (LMC) is one of the best sites to study this mechanism as we can observe the entire galactic disk without contamination and small distance uncertainty. For a statistical approach, a uniformly sampled massive star catalog is essential, but it is far from complete.
To overcome this situation, we identified massive stars in the LMC from the Gaia DR3 catalog, taking full advantage of its accurate optical photometry and color indices. Also star clusters are identified from their non-uniform distributions. As a result, we have identified more than 12,000 massive (> 8 Mo) star candidates and about 300 clusters. We then derived their age and Av by fitting to theoretical isochrone. Another notable advantage of the Gaia catalog is their high-precision proper motions. We subtracted the the galaxy bulk motion and rotation from each stellar motion and derived the internal proper motions of the clusters.
Thus derived massive star clusters exhibit highly non-uniform distributions, as several clusters are associated with major large HII regions such as N11, and N158. There are also numerous clusters distributed inside the Super Giant Shell LMC 4. Also we see a clear trend that neighboring clusters within a few 100 pc have similar proper motions and ages. This indicate that formation of those clusters did not occur independently, but rather have triggered by a common large-scale phenomena.
In the LMC, infalling HI clouds are suggested as a possible triggering mechanism to form the R136 cluster in 30 Dor (Fukui et al. 2017), and also in N44 (Tsuge et al. 2019). This is also supported by the existence of molecular filaments and their velocity structures (Wong et al. 2022; Maity et al. 2024). Our results provide another piece of evidence of the collisions of HI clouds on the LMC disk that triggered massive star formations in the entire LMC.
