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ALMA Band 9 CO(6-5) Reveals a Warm Ring Structure Associated with the Embedded Protostar in the Cold Dense Core MC 27/L1521F
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DOI：10.3847/2041-8213/ae47ec.png)
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Abstract
En 中文
Infall and outflows, coupled with magnetic fields, rapidly structure the gas around newborn protostars. Shocks from interacting components encode the temperature and density distribution, offering a direct probe of the earliest evolution history. However, interferometric observations characterizing warm envelopes using high-excitation lines remain scarce. We present Atacama Large Millimeter/submillimeter Array Band 9 observations of the Taurus dense core MC 27/L1521F, which hosts a Class 0 protostar, targeting the CO(J = 6-5) line at an angular resolution of similar to 2 '' (approximate to 300 au). We detect an off-centered ringlike structure with a diameter of similar to 1000 au that was not identifiable in previous low-J CO data, where emission close to the systemic velocity is strongly affected by optical depth. The ring shows a typical peak brightness temperature of similar to 3 K at our resolution. Excitation considerations indicate that the detected CO(J = 6-5) emission likely arises from relatively warm (T greater than or similar to 20 K) and dense (n(H2) greater than or similar to 105 cm-3) gas embedded within the surrounding cold, dense core. The morphology and kinematics suggest an energetic and localized shock-heating event, potentially linked to dynamical gas-magnetic-field interactions in the earliest protostellar phase. Our results demonstrate that high-J CO observations provide a powerful new window on warm and dense gas components, enabling a more direct view of the physical processes operating at the onset of star formation.
Keywords:
MAGNETIC INTERCHANGE INSTABILITY
MOLECULAR CLOUD CORES
CRA-IRS 2
STAR-FORMATION
CIRCUMSTELLAR DISK
INITIAL CONDITIONS
POSSIBLE SITE
TAURUS
GAS
I.
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11.7
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1.2W
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