2026-04-02 九州大学
図1: アルマ望遠鏡の観測に基づく分子雲コアMC 27内部の想像図。 右下にあるのが原始星およびその周りを取り巻く円盤であり、 そこからリング状に暖かいガスが広がっている。リングの内部には磁力線が貫いている。 (Credit: Y. Nakamura, K. Tokuda et al.)
＜関連情報＞
- https://www.kyushu-u.ac.jp/ja/researches/view/1454
- https://www.kyushu-u.ac.jp/f/65505/26_0402_01.pdf
- https://iopscience.iop.org/article/10.3847/2041-8213/ae47ec
ALMAバンド9 CO(6–5)により、低温高密度コアMC 27/L1521Fに埋め込まれた原始星に関連する高温リング構造が明らかになった ALMA Band 9 CO(6–5) Reveals a Warm Ring Structure Associated with the Embedded Protostar in the Cold Dense Core MC 27/L1521F
Kazuki Tokuda, Mitsuki Omura, Naoto Harada, Ayumu Shoshi, Naofumi Fukaya, Toshikazu Onishi, Kengo Tachihara, Kazuya Saigo, Tomoaki Matsumoto, Yasuo Fukui,…
The Astrophysical Journal Letters Published: 2026 April 2
DOI:10.3847/2041-8213/ae47ec
Abstract
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 ∼2″ (≈300 au). We detect an off-centered ringlike structure with a diameter of ∼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 ∼3 K at our resolution. Excitation considerations indicate that the detected CO(J = 6–5) emission likely arises from relatively warm (T ≳ 20 K) and dense (n(H2) ≳ 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.
