わずかな分子ガスを有する塵に満ちた地域から2つのG-rayバーストが発生した
B Hatsukade1, K Ohta2, A Endo3
1National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan.
Nature
|June 13, 2014
まとめ
長く続くガンマ線爆発は,塵に満ちた地域で発生しますが,驚くべきことに,豊富な分子ガスが欠けています. これは,巨大な恒星が爆発する前に密度の高いガスを放散し,恒星形成環境に影響を与える可能性があることを示唆しています.
科学分野:
- 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)
- ガンマ線爆発天文学のガンマ線爆発
背景:
- 長期ガンマ線爆発 (GRB) は,巨大な星の爆発から発生し,通常は分子ガスを含んだ恒星形成地域で見られる.
- 炭素一酸化物 (CO) 放出を用いた以前の研究では,GRBの宿主銀河の分子ガスを検出できませんでした.
- GRBの後発光線に沿って吸収された分子ガスは,拡散雲の性質を示唆しますが,一般的な環境を表していません.
研究 の 目的:
- 空間的に解像度のある観測を用いて,長期間続くGRBの近隣環境における分子ガスと塵の含有量を調査する.
- GRBの宿主領域が,大規模な恒星形成のために期待される分子ガス貯蔵庫を持っているかどうかを決定する.
主な方法:
- 炭素一酸化物 (CO) 線放射の空間的に解像度のある観測を行った.
- ミリメートル波長連続観測を行い,塵の軌跡をたどりました.
- 長期にわたるガンマ線爆発を宿している2つの銀河のデータを分析した.
主要な成果:
- 観測されたGRBを宿る地域は,塵が豊富だったが,特に有意な分子ガスが欠けていた.
- 典型的な恒星形成地域と比較して,分子ガスと塵の比率は低い (<9-14) ことが判明しました.
- これらの発見は,巨大な恒星が形成され爆発する環境で,豊富な分子ガスが期待されるものと相違しています.
結論:
- 低分子ガスと塵の比率は,恒星形成に必要な密度の高いガスがGRB環境で枯渇していることを示しています.
- 巨大な恒星は,最終的に爆発的に消滅する前に,フィードバックメカニズムを通じて周囲の分子ガスを散らばす可能性があります.
- これは,GRBが純粋でガスに富んだ恒星形成地域とだけ関連しているという単純な考え方に異議を唱える.
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