The Young Stellar Population in the Chamaeleon-Musca Dark Cloud Complex

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題名:	The Young Stellar Population in the Chamaeleon-Musca Dark Cloud Complex
作者:	陳湘喻;Chen, Hsiang Yu
貢獻者:	天文研究所
關鍵詞:	恆星形成;分子雲;蝘蜓座分子雲;蒼蠅座分子雲;Epsilon Cha 星協;star formation;molecular cloud;Chamaeleon;Musca;Epsilon Cha
日期:	2024-07-09
上傳時間:	2024-10-09 15:20:39 (UTC+8)
出版者:	國立中央大學
摘要:	內容. 蝘蜓—蒼蠅座分子雲的低質量恆星形成區距離太陽約 200 秒差距。前人文獻已經多次普查這些年輕恆星族群，但研究的範圍幾乎只聚焦在分子雲本身。目標. 為了診斷蝘蜓—蒼蠅座分子雲的恆星形成歷史，我們除了尋找在分子雲上的年輕成員星之外，也調查雲以外的區域。方法. 我們研究比前人文獻廣上許多的區域12◦ × 12◦，利用 Gaia DR3 提供的高度精確測光以及天體測量數據，加上近紅外波段 2MASS 與中紅外波段 ALLWISE 的顏色，尋找年輕恆星成員。結果. 我們確認蝘蜓 I 的恆星形成是這個區域中最活躍的，有近 200 顆的年輕恆星成員。蝘蜓 II 擁有 50 幾顆年輕恆星，而其中三顆位在蝘蜓 III 的北邊，但蝘蜓 III 本身沒有自己的恆星形成。蒼蠅座分子雲也沒有年輕恆星，但根據文獻它孕育了原恆星核，表示正處於誕生恆星的前期狀態。Cha I 的成員可以從距離分為南邊 189−5 +5 秒差距與北邊 193−3 +2 秒差距，而 Cha II 的成員星大約落在 197−5 +5 秒差距，這兩個年輕恆星族群的年齡大約是三百萬年。位在我們研究的恆星形成區的前景(約 110 秒差距)，我們找到一些 ε Cha 和下半人馬-南十字座的星協成員，他們是演化更久的年輕恆星或是主序星，年齡分佈廣從五百萬至兩千萬年。總結. 在分子雲裡的已知成員星，與我們新找到的雲外的成員星，有一致的距離與年齡，推測這可能是附近的 OB 星協影響蝘蜓—蒼蠅座分子雲的恆星誕生。;Context. The Chamaeleon-Musca dark cloud complex is a known low-mass star-forming region at a distance of ∼200 pc. The young stellar populations have been investigated in previous works, but mostly focused toward the main clouds. Aims. We searched for young members not only associated with the main clouds but also in intercloud regions in order to diagnose the star formation history of the entire complex. Method. By using Gaia DR3 data, which provide unprecedentedly precise photometry and astrometry for membership, and near- and mid-infrared photometry from 2MASS and ALLWISE for stellar youth, we investigate a sky area of 12◦ × 12◦ toward the cloud complex, much larger than previously reported in the literature. Results. We confirm that Cha I is active in star formation, with nearly 200 young members. There are more than 50 young members in Cha II, among which three are projected in northern Cha III which itself lacks any star-forming activity. The Musca cloud harbors no young star, though it is known to host prestellar cores. Cha I indeed as known has two subclusters, with the northern group at 193+2 −3 pc and the southern group at 189+5 −5 pc. Cha II is at 197+5 −5 pc, and has an age of about 3 Myr as in Cha I. Some members of ϵ Cha and Lower Centaurus-Crux associations projected in the foreground (∼110 pc) toward our studied region are found to be evolved young stars or dwarfs, with a wide age spread of ∼5–20 Myr. Conclusions. Our reliable sample of young stellar members provides accurate diagnosis of distance, age, and their relation to parental molecular clouds, including those already known in the literature, plus a few newly found offcloud members, suggesting a coeval star formation likely influenced by nearby OB stars. Thesis Supervisor: Wen-Ping Chen Title: Professor
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