Complex organic molecules and hot core chemistry in star-forming regions of the Magellanic Clouds with ALMA
Abstract
The Large and Small Magellanic Clouds (LMC and SMC) are the nearest laboratories for detailed studies on the formation and survival of complex organic molecules (COMs) in low-metallicity environments. Until recently, only a small and diverse sample of sources associated with COMs or hot core chemistry were known in the Magellanic Clouds: two hot cores with COMs (CH$ _{3}$OH, CH$ _{3}$OCH$ _{3}$, and HCOOCH$ _{3}$) and one hot core with no COMs in the LMC, and a handful of locations in the LMC and SMC with the detection of CH$ _{3}$OH, but outside hot cores (`cold methanol'). The fractional abundances of COMs in two LMC hot cores were found to be at the lower end of the range observed toward Galactic hot cores, while the upper limits determined for the hot core with no COMs were an order of magnitude lower. The number of sources in the LMC with COM detections has expanded significantly as a result of recent studies using the Atacama Large Millimeter/submillimeter Array (ALMA), targeting sites of massive star formation identified with Spitzer. A detection of a hot core in the LMC containing CH$ _{3}$OH and methyl cyanide (CH$ _{3}$CN; but no more complex molecules) has recently been reported in literature, while four hot cores have been found in a systematic study of 20 fields around massive YSOs in the LMC. Our observations of seven fields in the LMC having common characteristics with two known hot cores with COMs more complex than CH$ _{3}$OH resulted in a detection of at least six bona fide hot cores with three located in the star-forming region N105. The analysis of the N105 data reveals that methanol is widespread with an extended cold component and compact emission toward continuum sources. CH$ _{3}$CN is detected toward all hot cores together with smaller molecules such SO$ _{2}$, SO, or HNCO (typically found in Galactic hot cores). We also report a probable (six sigma) detection of a single line of the astrobiologically relevant formamide molecule (NH$ _{2}$CHO), toward one of the LMC hot cores. This is the first detection of NH$ _{2}$CHO in a low-metallicity environment. With the increased sample of hot cores in the LMC, we can start drawing reliable conclusions on the formation and evolution of COMs in the reduced metallicity environments by comparing their chemical and physical properties to those observed toward Galactic hot cores. The range of metallicities observed in the LMC and SMC are similar to galaxies at the peak of star formation in the Universe (redshift z$\sim$1.5-2), making them ideal templates for studying the star formation process and complex chemistry in low-metallicity systems at earlier cosmological epochs.
- Publication:
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43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1982S