Formation of the Young Massive Cluster R136 triggered by Tidally-driven Colliding HI Flows

TL;DR

This paper proposes that the formation of the young massive cluster R136 was triggered by a collision between two HI gas components in the LMC, driven by tidal interactions with the SMC, supported by observational and simulation data.

Contribution

It introduces a new hypothesis linking tidal-driven colliding HI flows to the formation of R136 and surrounding high-mass stars in the LMC.

Findings

Identification of colliding HI components near R136

Evidence of bridge features and complementary distributions

A proposed formation mechanism involving shock compression

Abstract

Understanding of massive cluster formation is one of the important issues of astronomy. By analyzing the HI data, we have identified that the two HI velocity components (L- and D-components) are colliding toward the HI Ridge, in the southeastern end of the LMC, which hosts the young massive cluster R136 and $\sim$400 O/WR stars (Doran et al. 2013) including the progenitor of SN1987A. The collision is possibly evidenced by bridge features connecting the two HI components and complementary distributions between them. We frame a hypothesis that the collision triggered the formation of R136 and the surrounding high-mass stars as well as the HI & Molecular Ridge. Fujimoto & Noguchi (1990) advocated that the last tidal interaction between the LMC and the SMC about 0.2 Gyr ago induced collision of the L- and D-components. This model is consistent with numerical simulations (Bekki & Chiba 2007b). We suggest that a dense HI partly CO cloud of 10$^{6}$ $M_{\odot}$, a precursor of R136, was formed at the shock-compressed interface between the colliding L- and D-components. We suggest that part of the low-metalicity gas from the SMC was mixed in the tidal interaction based on the $Planck/IRAS$ data of dust optical depth (Planck Collaboration et al. 2014).