ジェイムズ・ウェッブ宇宙望遠鏡が惑星形成の終焉を捉える(James Webb Space Telescope captures the end of planet formation)

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2024-02-05 アリゾナ大学

科学者は、太陽系のような惑星系には、ガス豊富なものよりも岩石の天体が多いと考えています。地球の周りには、水星、金星、地球、火星、小惑星帯、冥王星などが含まれます。一方で、木星、土星、天王星、海王星は主にガスから成っています。しかし、惑星形成ディスクは最初はガスが固体よりも100倍多くあります。これに関連して、アリゾナ大学月と惑星研究所のNaman Bajaj率いる新しい研究が、アストロノミカルジャーナルに発表されました。この研究では、ジェームズ・ウェッブ宇宙望遠鏡を使用して、ガスを周囲の空間に活発に分散させる過程で、新生惑星系(周囲星間円盤とも呼ばれる)から画像を取得しました。

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JWST MIRI MRSによるT Chaの観測: 空間的に分解された円盤風の発見 JWST MIRI MRS Observations of T Cha: Discovery of a Spatially Resolved Disk Wind

Naman S. Bajaj, Ilaria Pascucci, Uma Gorti,, Richard Alexander, Andrew Sellek,, Jane Morrison, Andras Gaspar, Cathie Clarke, Chengyan Xie, Giulia Ballabio +
The Astrophysical Journal  Published 2024 March 4
DOI:10.3847/1538-3881/ad22e1

ジェイムズ・ウェッブ宇宙望遠鏡が惑星形成の終焉を捉える(James Webb Space Telescope captures the end of planet formation)

Abstract

Understanding when and how circumstellar disks disperse is crucial to constrain planet formation and migration. Thermal winds powered by high-energy stellar photons have long been theorized to drive disk dispersal. However, evidence for these winds is currently based only on small (∼3–6 km s−1) blueshifts in [Ne ii] 12.81 μm lines, which does not exclude MHD winds. We report JWST MIRI MRS spectro-imaging of T Cha, a disk with a large dust gap (∼30 au in radius) and blueshifted [Ne ii] emission. We detect four forbidden noble gas lines, [Ar ii], [Ar iii], [Ne ii], and [Ne iii], of which [Ar iii] is the first detection in any protoplanetary disk. We use line flux ratios to constrain the energy of the ionizing photons and find that argon is ionized by extreme ultraviolet, whereas neon is most likely ionized by X-rays. After performing continuum and point-spread function subtraction on the integral field unit cube, we discover a spatial extension in the [Ne ii] emission off the disk continuum emission. This is the first spatially resolved [Ne ii] disk wind emission. The mostly ionic spectrum of T Cha, in combination with the extended [Ne ii] emission, points to an evolved stage for any inner MHD wind and is consistent with the existence of an outer thermal wind ionized and driven by high-energy stellar photons. This work acts as a pathfinder for future observations aiming at investigating disk dispersal using JWST.

1701物理及び化学
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