Giant Molecular Cloud Formation at the Interface of Colliding Supershells in the Large Magellanic Cloud

TL;DR

This study reveals that giant molecular clouds in the Large Magellanic Cloud form through gravitational instabilities in filamentary atomic gas accumulated and compressed by colliding supershells, highlighting the role of filamentary structures.

Contribution

It provides new high-resolution observations showing the filamentary structure of atomic gas and proposes a novel formation scenario for GMCs involving shell collisions.

Findings

Hi gas is highly filamentary with ~21 pc width filaments.

GMCs likely formed via gravitational instabilities in atomic gas.

Atomic gas was accumulated and compressed by colliding supershells.

Abstract

We investigate the Hi envelope of the young, massive GMCs in the star-forming regions N48 and N49, which are located within the high column density Hi ridge between two kpc-scale supergiant shells, LMC 4 and LMC 5. New long-baseline Hi 21 cm line observations with the Australia Telescope Compact Array (ATCA) were combined with archival shorter baseline data and single dish data from the Parkes telescope, for a final synthesized beam size of 24.75" by 20.48", which corresponds to a spatial resolution of ~ 6 pc in the LMC. It is newly revealed that the Hi gas is highly filamentary, and that the molecular clumps are distributed along filamentary Hi features. In total 39 filamentary features are identified and their typical width is ~ 21 (8-49) [pc]. We propose a scenario in which the GMCs were formed via gravitational instabilities in atomic gas which was initially accumulated by the two shells and then further compressed by their collision. This suggests that GMC formation involves the filamentary nature of the atomic medium.