Growth of aromatic hydrocarbon dust particles in the extremely metal-poor galaxy Sextans A

IF 15.2 1区物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS

Nature Astronomy Pub Date : 2026-09-29 DOI:10.1038/s41550-026-02969-5

Elizabeth J. Tarantino, Julia Roman-Duval, Karin M. Sandstrom, Cory M. Whitcomb, J.-D. T. Smith, Bruce T. Draine, Martha L. Boyer, Jérémy Chastenet, Ryan Chown, Christopher J. R. Clark, Meriem Elyajouri, Karl D. Gordon, Brandon S. Hensley, Thomas S.-Y. Lai, Christina W. Lindberg, Kristen B. W. McQuinn, Max J. B. Newman, O. Grace Telford, Dries Van De Putte, Benjamin F. Williams

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Abstract

The mid-infrared spectrum of star-forming, high-metallicity galaxies is dominated by emission features from aromatic and aliphatic bonds in small carbonaceous dust grains, often referred to as polycyclic aromatic hydrocarbons (PAHs). In metal-poor galaxies, the abundance of PAHs relative to the total dust sharply declines, but the origin of this deficit is unknown. Here we present observations by the James Webb Space Telescope that detect and resolve emission from PAHs in the 7% solar metallicity galaxy Sextans A, representing, to our knowledge, the lowest metallicity detections of PAH emission known so far. In contrast to higher metallicity galaxies, the clumps of PAH emission are compact (0.5–1.5" or 3–10 pc), which explains why PAH emission has evaded detection by lower resolution instruments. Ratios of the 3.3-μm, 7.7-μm and 11.3-μm PAH features indicate that the PAH grains in Sextans A are small and neutral, with no evidence of substantial processing from radiation fields. These results favour inhibited grain growth over enhanced destruction as the origin of the low PAH abundance in Sextans A. The compact clumps of PAH emission are likely active sites of in situ PAH growth within a dense, well-shielded phase of the interstellar medium. Our results show that PAHs can form and survive in the extremely metal-poor environments common early in the evolution of the Universe.

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六分星A中极度缺乏金属的芳烃尘埃颗粒的生长

恒星形成的高金属丰度星系的中红外光谱主要由小碳质尘埃颗粒中的芳香族和脂肪键的发射特征所主导，通常被称为多环芳香族烃（PAHs）。在金属贫乏的星系中，多环芳烃的丰度相对于总尘埃急剧下降，但这种赤字的来源尚不清楚。在这里，我们展示了詹姆斯·韦伯太空望远镜对太阳系金属丰度为7%的六分星A中多环芳烃发射的探测和解析结果，据我们所知，这是迄今为止已知的金属丰度最低的多环芳烃发射探测结果。与金属丰度较高的星系相比，多环芳烃的发射团块非常紧凑（0.5-1.5英寸或3-10英寸），这就解释了为什么低分辨率仪器无法探测到多环芳烃的发射。3.3 μm、7.7 μm和11.3 μm多环芳烃特征的比值表明六分体A中的多环芳烃颗粒较小且呈中性，没有受到辐射场的大量加工。这些结果有利于抑制颗粒生长，而不是增强破坏，这是六分星a中多环芳烃丰度低的原因。多环芳烃发射的致密团块可能是星际介质中致密、屏蔽良好的相中多环芳烃原位生长的活性位点。我们的研究结果表明，多环芳烃可以在宇宙演化早期常见的极度缺乏金属的环境中形成和生存。

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来源期刊

Nature Astronomy Physics and Astronomy-Astronomy and Astrophysics

CiteScore

19.50

自引率

2.80%

发文量

252

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