2023-11-20 ノースウェスタン大学
◆CECILIAサーベイは遠くの銀河のスペクトルを調査し、銀河の成長と進化を理解することを目的としています。研究では、ジェームズ・ウェッブ宇宙望遠鏡を使用して33のティーンエイジギャラクシーを観測し、そのスペクトルから8つの異なる元素を検出。特に、通常観測が難しいニッケルの存在に驚き、ギャラクシーが若い頃に異なる化学的DNAを持っていた可能性が示唆されました。
＜関連情報＞
- https://news.northwestern.edu/stories/2023/11/teenage-galaxies-are-unusually-hot-glowing-with-unexpected-elements/
- https://iopscience.iop.org/article/10.3847/2041-8213/ad07dc
CECILIA: z ∼ 2-3 星形成銀河のかすかな輝線スペクトル CECILIA: The Faint Emission Line Spectrum of z ∼ 2–3 Star-forming Galaxies
Allison L. Strom, Gwen C. Rudie, Ryan F. Trainor, Gabriel B. Brammer, Michael V. Maseda, Menelaos Raptis, Noah S. J. Rogers, Charles C. Steidel, Yuguang Chen (陈昱光), and David R. Law
The Astrophysical Journal Letters Published 2023 November 20
DOI:10.3847/2041-8213/ad07dc
Abstract
We present the first results from Chemical Evolution Constrained Using Ionized Lines in Interstellar Aurorae (CECILIA), a Cycle 1 JWST NIRSpec/MSA program that uses ultra-deep ∼30 hr G235M/F170LP observations to target multiple electron temperature-sensitive auroral lines in the spectra of 33 galaxies at z ∼ 1–3. Using a subset of 23 galaxies, we construct two ∼600 object-hour composite spectra, both with and without the stellar continuum, and use these to investigate the characteristic rest-optical (λrest ≈ 5700–8500 Å) spectrum of star-forming galaxies at the peak epoch of cosmic star formation. Emission lines of eight different elements (H, He, N, O, Si, S, Ar, and Ni) are detected, with most of these features observed to be ≲3% the strength of Hα. We report the characteristic strength of three auroral features ([N ii]λ5756, [S iii]λ6313, and [O ii]λλ7322, 7332), as well as other semi-strong and faint emission lines, including forbidden [Ni ii]λλ7380, 7414 and permitted O iλ8449, some of which have never before been observed outside of the local Universe. Using these measurements, we find Te[N ii] = 13,630 ± 2540 K, representing the first measurement of electron temperature using [N ii] in the high-redshift Universe. We also see evidence for broad line emission with a FWHM of 536+45−167 km s−1; the broad component of Hα is 6.01%–28.31% the strength of the narrow component and likely arises from star-formation-driven outflows. Finally, we briefly comment on the feasibility of obtaining large samples of faint emission lines using JWST in the future.
