褐色矮星はどのように形成されるのか?(Astronomy: How do brown dwarfs form?)

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2024-04-04 ミュンヘン大学(LMU)

星の誕生は複雑なプロセスで、初期段階では螺旋状や流れなどのガス構造が重要です。これらの構造は新生星に周囲の気体を供給する「給餌フィラメント」と呼ばれ、宇宙の臍帯のような役割を果たします。最新の観測では、若いブラウンドワーフであるSer-emb 16周辺に広がる複雑な構造が発見され、これらはブラウンドワーフの形成プロセスを示唆します。これにより、星のような動的な形成プロセスが明らかになり、重力崩壊や磁場の役割が理解されました。

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原始褐色矮星候補のスパイラルとストリーマの観測 Observations of spiral and streamer on a candidate proto-brown dwarf

B Riaz, D Stamatellos, M N Machida
Monthly Notices of the Royal Astronomical Society  Published:11 March 2024
DOI:https://doi.org/10.1093/mnras/stae724

(a–b) ALMA 1.16 mm continuum image. (c) ALMA HCO$^{+}$ (3-2) spectrum. Dashed line marks the V$_{\mathrm{ lsr}}$ for Ser-emb 16. (d) The moment 8 maps of the blue-shifted spiral and red-shifted streamer overplotted in positions. The contours are from 2$\sigma$ to 10$\sigma$ in steps of 2$\sigma$. The 1$\sigma$ rms is $\sim$10 mJy beam$^{-1}$. Ser-emb 16 continuum position is marked by a star.

ABSTRACT

Spirals and streamers are the hallmarks of mass accretion during the early stages of star formation. We present the first observations of a large-scale spiral and a streamer towards a very young brown dwarf candidate in its early formation stages. These observations show, for the first time, the influence of external environment that results in asymmetric mass accretion via feeding filaments on to a candidate proto-brown dwarf in the making. The impact of the streamer has produced emission in warm carbon-chain species close to the candidate proto-brown dwarf. Two contrasting scenarios, a pseudo-disc twisted by core rotation and the collision of dense cores, can both explain these structures. The former argues for the presence of a strong magnetic field in brown dwarf formation while the latter suggests that a minimal magnetic field allows large-scale spirals and clumps to form far from the candidate proto-brown dwarf.

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1701物理及び化学
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