The Detection of Hot Molecular Cores in the Small Magellanic Cloud

Shimonishi, Takashi; Tanaka, Kei E. I.; Zhang, Yichen; Furuya, Kenji

doi:10.3847/2041-8213/acc031

Cited by 4 publications

(1 citation statement)

References 44 publications

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“…of ∼ 1.2 mJy beam −1 for continuum and ∼ 4.7 mJy per channel for lines, we could easily observe molecular emission lines that could not be found in previous lower resolution observations (Shimonishi et al 2023).…”

Section: Alma Observations and Data Reductionsupporting

confidence: 38%

ALMA High-resolution Spectral Survey of Thioformaldehyde (H₂CS) toward Massive Protoclusters

Chen,

Qin,

Liu

et al. 2024

ApJ

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Investigating the temperature and density structures of gas in massive protoclusters is crucial for understanding the chemical properties therein. In this study, we present observations of the continuum and thioformaldehyde (H2CS) lines at 345 GHz of 11 massive protoclusters using the Atacama Large Millimeter/submillimeter Array telescope. High spatial resolution and sensitivity observations have detected 145 continuum cores from the 11 sources. H2CS line transitions are observed in 72 out of 145 cores, including line-rich cores, warm cores, and cold cores. The H2 column densities of the 72 cores are estimated from the continuum emission, which are larger than the density threshold value for star formation, suggesting that H2CS can be widely distributed in star-forming cores with different physical environments. The rotation temperature and column density of H2CS are derived using the XCLASS software. The results show that the H2CS abundances increase as temperature rises and higher gas temperatures are usually associated with higher H2CS column densities. The abundances of H2CS are positively correlated with its column density, suggesting that the H2CS abundances are enhanced from cold cores, warm cores, and line-rich cores in star-forming regions.

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Section: Alma Observations and Data Reductionsupporting

confidence: 38%

ALMA High-resolution Spectral Survey of Thioformaldehyde (H₂CS) toward Massive Protoclusters

Chen,

Qin,

Liu

et al. 2024

ApJ

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High-mass star formation across the Large Magellanic Cloud

Golshan,

Sánchez-Monge,

Schilke

et al. 2024

A&A

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The formation of massive stars passes through a so-called hot molecular core phase, where the temperature of molecular gas and dust rises to above 100 K within a size scale of approximately 0.1 pc. The hot molecular cores are rich in chemical compounds found in the gas phase, which are a great probe of ongoing star formation. To study the impact of the initial effects of metallicity (i.e., the abundance of elements heavier than helium) on star formation and the formation of different molecular species, we searched for hot molecular cores in the sub-solar metallicity environment of the Large Magellanic Cloud (LMC). We conducted Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations of 20 fields centered on young stellar objects (YSOs) distributed over the LMC in order to search for hot molecular cores in this galaxy. We detected a total of 65 compact 1.2 mm continuum cores in the 20 ALMA fields and analyzed their spectra with XCLASS software. The main temperature tracers are CH3OH and SO2 with more than two transitions detected in the observed frequency ranges. Other molecular lines with high detection rates in our sample are CS SO H^ CO^+ H^ CN HC^ N and SiO . More complex molecules, such as HNCO HDCO HC3N CH3CN and NH2CHO and multiple transitions of SO and SO2 isotopologues showed tentative or definite detection toward a small subset of the cores. According to the chemical richness of the cores and high temperatures from the XCLASS fitting, we report the detection of four hot cores and one hot core candidate. With one new hot core detection in this study, the number of detected hot cores in the LMC increases to seven. Six out of seven hot cores detected in the LMC to date are located in the stellar bar region of this galaxy. These six hot cores show emission from complex organic molecules (COMs), such as CH3OH CH3CN CH3OCHO and CH3OCH3 . The only known hot core in the LMC with no detection of COMs is located outside the bar region. The metallicity in the LMC presents a shallow gradient increasing from outer regions toward the bar. Various studies emphasize the interaction between the LMC and the Small Magellanic Cloud, which resulted in the mixing and inhomogeneity of the interstellar medium of the two galaxies. These interactions triggered a new generation of star formation in the LMC. We suggest that the formation of hot molecular cores containing COMs ensues from the new generation of stars forming in the more metal-rich environment of the LMC bar.

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Understanding the various evolutionary stages of the low-mass star-formation process by SO and SO2

Ghosh,

Das,

Gorai

et al. 2024

Front. Astron. Space Sci.

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SO and SO2 are two potential candidates to trace the different evolutionary phases of the low-mass star-formation process. Here, we report observations of SO and SO2 along with their isotopologues, 34SO and 34SO2, respectively, in four distinct phases of the low-mass star-formation process (prestellar core, first hydrostatic core, Class 0, and Class I) with an unbiased survey carried out using the Institut de Radioastronomie Millimetrique (IRAM) 30 m telescope. Interestingly, the estimated abundances of SO and SO2 show an increasing trend from the prestellar phase to the Class 0 stage and then a decrease in the Class I phase. A similar trend is obtained for OCS and H2S. In contrast, the obtained SO/SO2 ratio decreases gradually from the prestellar core to the Class I stage. We have used the three-phase Rokko chemical code to explain our observations. The modeled abundances of SO and SO2 exhibit an increase within the inner region as the cold gas transforms into a hot gas. The modeled abundance ratio of SO to SO2 exhibits a notably high value in cold gas environments. This ratio decreases to less than 1 within the temperature range of 100–300 K and then increases to approximately 1 beyond 300 K. In the outer region, the simulated ratio consistently exceeds the value of 1. Our work is an observational testbed for modeling the chemistry of SO/SO2 during low-mass star formation. However, our findings may require more sample sources with higher resolution and a more robust model for validation.

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The Detection of Hot Molecular Cores in the Small Magellanic Cloud

Cited by 4 publications

References 44 publications

ALMA High-resolution Spectral Survey of Thioformaldehyde (H₂CS) toward Massive Protoclusters

ALMA High-resolution Spectral Survey of Thioformaldehyde (H₂CS) toward Massive Protoclusters

High-mass star formation across the Large Magellanic Cloud

Understanding the various evolutionary stages of the low-mass star-formation process by SO and SO2

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The Detection of Hot Molecular Cores in the Small Magellanic Cloud

Cited by 4 publications

References 44 publications

ALMA High-resolution Spectral Survey of Thioformaldehyde (H2CS) toward Massive Protoclusters

ALMA High-resolution Spectral Survey of Thioformaldehyde (H2CS) toward Massive Protoclusters

High-mass star formation across the Large Magellanic Cloud

Understanding the various evolutionary stages of the low-mass star-formation process by SO and SO2

Contact Info

Product

Resources

About

ALMA High-resolution Spectral Survey of Thioformaldehyde (H₂CS) toward Massive Protoclusters

ALMA High-resolution Spectral Survey of Thioformaldehyde (H₂CS) toward Massive Protoclusters