Formation of the active star forming region LHA 120-N 44 triggered by tidally-driven colliding HI flows

TL;DR

This study analyzes HI gas dynamics in the LHA 120-N 44 star-forming region of the LMC, revealing colliding gas flows likely triggered by tidal interactions, leading to active high-mass star formation.

Contribution

It provides a detailed decomposition of HI velocity components and links their collision to star formation, highlighting the role of tidal interactions in triggering activity.

Findings

Identification of three HI velocity components (L-, D-, I-)

Evidence of colliding HI flows triggering star formation

Correlation between dust optical depth and HI intensity with regional variations

Abstract

N44 is the second active site of high mass star formation next to R136 in the Large Magellanic Cloud (LMC). We carried out a detailed analysis of HI at 60 arcsec resolution by using the ATCA & Parkes data. We presented decomposition of the HI emission into two velocity components (the L- and D-components) with the 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 (Alves et al. 2000). Toward the active cluster forming region of LHA 120-N 44, the three velocity components of HI 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 Myrs 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 sub-mm dust optical depth is correlated with the HI 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 with the SMC 0.2 Gyrs ago.