TY - JOUR
T1 - THE DETECTION of A HOT MOLECULAR CORE in the LARGE MAGELLANIC CLOUD with ALMA
AU - Shimonishi, Takashi
AU - Onaka, Takashi
AU - Kawamura, Akiko
AU - Aikawa, Yuri
N1 - Funding Information:
was supported by the ALMA Japan Research Grant of NAOJ Chile Observatory, NAOJ-ALMA-0061. This work is supported by a Grant-in-Aid from the Japan Society for the Promotion of Science (15K17612).
Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved..
PY - 2016/8/10
Y1 - 2016/8/10
N2 - We report the first detection of a hot molecular core outside our Galaxy based on radio observations with ALMA toward a high-mass young stellar object (YSO) in a nearby low metallicity galaxy, the Large Magellanic Cloud (LMC). Molecular emission lines of CO, C17O, HCO+, H13CO+, H2CO, NO, SiO, H2CS, 33SO, 32SO2, 34SO2, and 33SO2 are detected from a compact region (∼0.1 pc) associated with a high-mass YSO, ST11. The temperature of molecular gas is estimated to be higher than 100 K based on rotation diagram analysis of SO2 and 34SO2 lines. The compact source size, warm gas temperature, high density, and rich molecular lines around a high-mass protostar suggest that ST11 is associated with a hot molecular core. We find that the molecular abundances of the LMC hot core are significantly different from those of Galactic hot cores. The abundances of CH3OH, H2CO, and HNCO are remarkably lower compared to Galactic hot cores by at least 1-3 orders of magnitude. We suggest that these abundances are characterized by the deficiency of molecules whose formation requires the hydrogenation of CO on grain surfaces. In contrast, NO shows a high abundance in ST11 despite the notably low abundance of nitrogen in the LMC. A multitude of SO2 and its isotopologue line detections in ST11 imply that SO2 can be a key molecular tracer of hot core chemistry in metal-poor environments. Furthermore, we find molecular outflows around the hot core, which is the second detection of an extragalactic protostellar outflow. In this paper, we discuss the physical and chemical characteristics of a hot molecular core in the low metallicity environment.
AB - We report the first detection of a hot molecular core outside our Galaxy based on radio observations with ALMA toward a high-mass young stellar object (YSO) in a nearby low metallicity galaxy, the Large Magellanic Cloud (LMC). Molecular emission lines of CO, C17O, HCO+, H13CO+, H2CO, NO, SiO, H2CS, 33SO, 32SO2, 34SO2, and 33SO2 are detected from a compact region (∼0.1 pc) associated with a high-mass YSO, ST11. The temperature of molecular gas is estimated to be higher than 100 K based on rotation diagram analysis of SO2 and 34SO2 lines. The compact source size, warm gas temperature, high density, and rich molecular lines around a high-mass protostar suggest that ST11 is associated with a hot molecular core. We find that the molecular abundances of the LMC hot core are significantly different from those of Galactic hot cores. The abundances of CH3OH, H2CO, and HNCO are remarkably lower compared to Galactic hot cores by at least 1-3 orders of magnitude. We suggest that these abundances are characterized by the deficiency of molecules whose formation requires the hydrogenation of CO on grain surfaces. In contrast, NO shows a high abundance in ST11 despite the notably low abundance of nitrogen in the LMC. A multitude of SO2 and its isotopologue line detections in ST11 imply that SO2 can be a key molecular tracer of hot core chemistry in metal-poor environments. Furthermore, we find molecular outflows around the hot core, which is the second detection of an extragalactic protostellar outflow. In this paper, we discuss the physical and chemical characteristics of a hot molecular core in the low metallicity environment.
KW - ISM: abundances
KW - ISM: molecules
KW - Magellanic Clouds
KW - astrochemistry
KW - circumstellar matter
KW - radio lines: ISM
UR - http://www.scopus.com/inward/record.url?scp=84982144146&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84982144146&partnerID=8YFLogxK
U2 - 10.3847/0004-637X/827/1/72
DO - 10.3847/0004-637X/827/1/72
M3 - Article
AN - SCOPUS:84982144146
VL - 827
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - 72
ER -