重要な原始星形成は赤偏移 z 約3〜4で発生しています
1Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, Pennsylvania 19104, USA. raulj@physics.upenn.edu
Nature
|March 24, 2006
まとめ
重元素で濃縮されていない原始恒星は,初期の銀河からの謎めいた紫外線と放射線データを説明します. この発見は,高赤偏移の銀河における非効率な金属混合を示唆している.
科学分野:
- 天文学と天体物理学について
- 宇宙進化の宇宙進化について
- 銀河の形成 銀河の形成
背景:
- 高赤偏移の銀河の最近の観測は,紫外線 (UV) の光子放出とスペクトル線の異常を示している.
- 具体的には,ライマンブレイク銀河 (LBGs) は予期せぬ紫外線とライマンアルファ放射,そして強いHe II放射線を示し,既存のモデルに挑戦しています.
研究 の 目的:
- 高赤道移転銀河に関する複数の観測パズルの現在の説明の矛盾を解決する.
- 初期の銀河における異常な紫外線と放射線特性を説明する統一モデルを提案する.
主な方法:
- 紫外線と放射線スペクトルに焦点を当てて,赤道偏移が大きい銀河からの観測データの分析.
- 銀河形成シナリオのモデリングには,原始的な恒星集団と金属の混合の度合いが異なる.
主要な成果:
- レッドシフト z ≈ 3-4 の銀河の原始的な (金属のない) 恒星を10-30%含むモデルは,同時に4つの主要な観測課題を解決します.
- これらの課題には,過剰な紫外線放射,拡張された領域からのライマン・アルファ放射,強いライマン・アルファ線,およびHe II放射線の存在が含まれます.
結論:
- 初期の銀河の原始星の大部分の存在は,観測された現象の実行可能な説明です.
- これは,多くの階層的な銀河形成モデルとは対照的に,銀河内の金属の非効率的なマイクロミキシングを,ギガガイアの時間スケールで意味しています.
- 将来の高解像度シミュレーションとHe II排出線観測により,この結論が確認できます.
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