雲の中の一酸化炭素は,小型の不規則な銀河WLMの低金属性である
Bruce G Elmegreen1, Monica Rubio, Deidre A Hunter
1IBM Research Division, T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598, USA. bge@us.ibm.com
Nature
|March 30, 2013
まとめ
炭素一酸化物 (CO) は金属度が低い銀河で検出され,星形成に関する以前の仮定に異議を唱えました. この発見は,銀河の金属性が減少するにつれて,星形成とCO分子が分子雲の中で希少になることを示唆しています.
科学分野:
- 天文学 天文学
- 天体物理学 天体物理学
- コスミック・スター・フォーメーション (宇宙の恒星形成)
背景:
- 一酸化炭素 (CO) は,恒星形成の星間雲の主要なトレーサーである.
- COは,酸素濃度が太陽値の20%未満の銀河系では検出されていないため,金属度が低い環境での恒星形成に関する疑問が生じています.
研究 の 目的:
- 低金属性銀河におけるCOの存在を調査する.
- 低金属度のある環境における恒星形成におけるCOの役割を理解する.
主な方法:
- 新しいサブミリメートル観測を用いた.
- アーカイブの遠赤外線観測を分析した.
- WLM銀河の推定雲質量について.
主要な成果:
- WLM矮小不規則銀河の2つの領域でCOが検出され,金属性は太陽値の13%である.
- 推定される雲の質量は10万太陽質量を超えています.
- COの分子ガス分子は,銀河系値の3%であることが判明しました.
結論:
- 恒星形成は,豊富なCOのない低金属性銀河で起こり得る.
- 恒星形成の核とCO分子は,小銀河の金属性が減少するにつれて,分子水素雲の中で稀になっていきます.
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