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輝く円銀河の低質量恒星の大群
Pieter G van Dokkum1, Charlie Conroy
1Astronomy Department, Yale University, New Haven, Connectitcut, USA. pieter.vandokkum@yale.edu
Nature
|December 3, 2010
まとめ
初期の宇宙の銀河は,これまで考えられていたよりもはるかに多くの低質量恒星を形成した. 観測により,低質量恒星が円銀河の恒星群を支配していることが明らかになり,恒星初期質量関数 (IMF) の理解に影響を与えています.
科学分野:
- 天体物理学 天体物理学
- 恒星の進化について
- 銀河系天文学 銀河系天文学
背景:
- 恒星の初期質量関数 (IMF) は,天体物理学にとって極めて重要であるが,銀河系外および初期の宇宙の文脈ではあまり制約されない.
- 以前の研究では,遠い銀河におけるIMFの決定的な特徴付けのための信号対ノイズ比が欠けていました.
研究 の 目的:
- 低質量星のスペクトルシグネチャを使用して円銀河におけるIMFを調査する.
- 初期の銀河の恒星全体の質量に対する低質量恒星の豊富さと貢献を決定する.
主な方法:
- 観測されたNa (I) ダブレットとウィング・フォード分子FeH帯は,円銀河のスペクトルで観測された.
- 分析されたスペクトル線は,質量が0.3太陽質量未満の恒星を示す.
- 線の強さを解釈して,低質量星の存在と豊富さを推測する.
主要な成果:
- 円銀河の低質量恒星のスペクトルシグネチャーを明確に検出しました.
- 発見された低質量恒星は,恒星集団の80%以上,恒星質量の60%以上を占めています.
- ミルクウェイの円盤と比較して,低質量星の割合が著しく高いことを示した.
結論:
- 巨大な初期の恒星形成銀河のIMFは,天の川よりも多くの低質量恒星を生成する方向に傾いていた.
- 初期の宇宙のIMFは,0.1~1太陽質量間のサルペテール形よりも急落していたのかもしれない.
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