ALMA Observations of Molecular Complexity in the Large Magellanic Cloud: The N105 Star-Forming Region

TL;DR

This study uses ALMA to investigate complex organic molecules in the N105 star-forming region of the Large Magellanic Cloud, revealing diverse chemical compositions and potential first extragalactic detection of formamide in a low-metallicity environment.

Contribution

First detailed ALMA molecular line study of N105 in the LMC, identifying hot cores and detecting complex molecules including a tentative formamide detection in an extragalactic setting.

Findings

Detected widespread CH₃OH emission across sources.

Identified two bona fide hot cores and four candidates.

Tentative detection of formamide (NH₂CHO) in an extragalactic environment.

Abstract

The Large Magellanic Cloud (LMC) is the nearest laboratory for detailed studies on the formation and survival of complex organic molecules (COMs), including biologically important ones, in low-metallicity environments--typical for earlier cosmological epochs. We report the results of 1.2 mm continuum and molecular line observations of three fields in the star-forming region N105 with the Atacama Large Millimeter/submillimeter Array (ALMA). N105 lies at the western edge of the LMC bar with on-going star formation traced by H$_2$O, OH, and CH$_3$OH masers, ultracompact H II regions, and young stellar objects. Based on the spectral line modeling, we estimated rotational temperatures, column densities, and fractional molecular abundances for twelve 1.2 mm continuum sources. We identified sources with a range of chemical make-ups, including two bona fide hot cores and four hot core candidates. The CH$_3$OH emission is widespread and associated with all the continuum sources. COMs CH$_3$CN and CH$_3$OCH$_3$ are detected toward two hot cores in N105 together with smaller molecules typically found in Galactic hot cores (e.g., SO$_2$, SO, and HNCO) with the molecular abundances roughly scaling with metallicity. We report a tentative detection of the astrobiologically relevant formamide molecule (NH$_2$CHO) toward one of the hot cores; if confirmed, this would be the first detection of NH$_2$CHO in an extragalactic sub-solar metallicity environment. We suggest that metallicity inhomogeneities resulting from the tidal interactions between the LMC and the Small Magellanic Cloud (SMC) might have led to the observed large variations in COM abundances in LMC hot cores.