حلقة حرارة في مهد نجم سريع

الملخص الأصلي

كما كتبه المؤلفون، بالإنجليزية arXiv:2602.12661

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 ALMA 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 $$\sim$$2\arcsec\ ($$\approx$$300 au). We detect an off-centered ring-like structure with a diameter of $$\sim$$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 $$\sim$$3 K at our resolution. Excitation considerations indicate that the detected CO($$J$$=6-5) emission likely arises from relatively warm ($$T \gtrsim 20$$ K) and dense ($$n({\rm H_2}) \gtrsim 10^{5}$$ 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.