2026-06-02 自然科学研究機構
図1：オリオン座分子雲の重水素割合に基づく進化地図。カラーが進化段階を示し、黄色が一番若く、濃紺が一番古い。オリオン大星雲の中心にあるKL星雲（巨大赤ちゃん星が誕生している）が四角で示してあり、有名なトラペジウムもこの近くである。図の北（上）から真ん中にかけて、黄色や黄緑の領域があり、ここでは天文学的*に近い将来、星が誕生すると期待される。 (* 10万年単位の時間スケールで）
＜関連情報＞
- https://www.nro.nao.ac.jp/news/2026/0602-tatematsu.html
- https://iopscience.iop.org/article/10.3847/1538-4365/ae5637
オリオン分子雲の∫型フィラメントおよび星のないコアに対するDNCおよびDCO +の観測 Observations of DNC and DCO+ toward the ∫-shaped Filament and Starless Cores in the Orion Molecular Clouds
Ken’ichi Tatematsu, Atsushi Nishimura, Hideo Ogawa, Nami Sakai, Takeshi Sakai, Kazuki Tokuda, Yutaka Hasegawa, Yasumasa Yamasaki, Toshikazu Onishi, Naomi Hirano,…
The Astrophysical Journal Supplement Series Published: 2026 April 29
DOI:10.3847/1538-4365/ae5637
Abstract
Although the deuterium fraction is known to be a powerful evolutionary tracer, its variation within individual molecular cloud cores is still poorly understood. The northern ∫-shaped filament and 20 individual starless cores in the Orion A and B clouds were mapped in the deuterated molecules of DNC and DCO+ with the receiver 7BEE installed on the Nobeyama 45 m radio telescope. In a ～5’×30’ map of the northern ∫-shaped filament in the Orion A cloud, the DNC emission is detected over the filament, whereas the DCO+ emission is localized toward OMC-3, the northernmost region of the filament. The difference in distribution between DNC and DCO+ can be attributed to that between N- and C-bearing molecules as previously suggested by K. Tatematsu et al. (2008). High DNC/HN13C column density ratios were observed in OMC-2 and OMC-3, and low ratios in OMC-1. It seems that OMC-2 and OMC-3 still contain molecular gas close to the onset of star formation. In 3’×3’ maps of the individual starless cores in Orion, the column density ratios of DNC/HN13C and DCO+/H13CO+ were found to be rather constant locally within each core, although the core-to-core variation is not small. Similar timescales of deuterization, depletion, and dynamical evolution might explain the locally constant ratio.
