用JWST/MIRI MRS解析红移z≈1星系中的尘埃：巡天描述及多环芳烃、中红外原子发射与 warm H₂ 的初步观测
Resolved Dust in $z\approx1$ Galaxies with JWST/MIRI MRS: Survey Description and First View on PAHs, Mid-IR Atomic Emission, and Warm H$_2$
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中文总结 AI 辅助
本研究利用JWST/MIRI MRS对8个z≈1星系开展高分辨率观测，测绘PAHs等发射，发现中心PAH颗粒更大、电离度更低，AGN与并合星系中性PAH占比更高，还揭示了潜在演化趋势。
中文摘要 AI 辅助
尘埃是星系的关键组成部分，调控着星系的热平衡，进而影响恒星形成与恒星质量的累积。多环芳烃（PAHs）负责再处理星系的辐射能量，因此可作为尘埃演化的示踪物。我们利用JWST/MIRI MRS，对8个红移z≈1的星系样本开展了首个高分辨率的PAHs与中红外发射线观测。本研究的核心创新在于，能在宇宙正午末期的阶段，于JWST的观测极限下直接测绘PAH发射。样本选取自恒星形成主序，恒星质量M★=10^(10.6-11.2) M☉，红外光度L_IR=10^(11.5-11.9) L☉；其中2个包含活动星系核（AGN），2个为并合系统。我们在整个星系范围内探测并量化了3.3μm至11.3μm的主要PAH发射，同时检测到原子精细结构线（Ar、Ne、Fe）、Brα及H₂转动跃迁。通过PAH比率诊断并与理论模型对比，我们定性探测了PAH分子的物理性质，即尺寸与电荷。样本中的AGN和并合星系表现出更高的中性PAH占比，这可能与高辐射强度和/或激波相关，而原子与H₂线比率的升高也支持这一结论。借助积分场单元（IFU）数据，我们发现星系中心区域的PAH颗粒尺寸往往比星系外围更大，且电离程度更低。最后，我们将结果与本地及相似红移星系的PAH观测对比，发现在控制L_IR的情况下存在潜在的演化趋势。
英文摘要
Dust is a key component of galaxies that regulates their thermal balance and, consequently, star formation and the build-up of stellar mass. Polycyclic aromatic hydrocarbons (PAHs) are responsible for reprocessing radiative energy of the galaxies thus tracing dust evolution. Using JWST/MIRI MRS, we present the first resolved view of the PAHs and mid-infrared emission lines in a sample of eight $z\approx1$ galaxies. A key novelty is our ability to directly map PAH emission near the end of cosmic noon at JWST's limits. The sample is selected to be on the star-forming main-sequence with stellar masses $M_{\star}=10^{10.6-11.2}\,M_{\odot}$ and infrared luminosities $L_{\rm IR}=10^{11.5-11.9}\,L_{\odot}$. Two of them contain active galactic nuclei (AGN), and two are interacting systems. We detect and quantify primary PAH emissions from 3.3$\,\rm μm$ to 11.3$\,\rmμm$ throughout the galaxies, alongside atomic fine structure lines (Ar, Ne, and Fe), Br$α$, and H$_{2}$ rotational transitions. Through PAH ratio diagnostics and comparison to theoretical models, we qualitatively probe the physical properties of PAH molecules, i.e., size and charge. The AGN and mergers in our sample exhibit a higher fraction of neutral PAHs, possibly related to high radiation intensity and/or shocks, as suggested by increased atomic and H$_{2}$ line ratios. Leveraging the IFU data, we find that the grain sizes of the centrally located PAHs tend to be larger and less ionized than those in the outskirts of the galaxies. Finally, we compare our results to observations of PAHs in local and similar-redshift galaxies, revealing a potential evolutionary trend when controlling $L_{\rm IR}$.
发表机构
- Caltech/IPAC（加州理工学院/IPAC）
- Department of Astronomy, The University of Texas at Austin（德克萨斯大学奥斯汀分校天文学系）
- Cosmic Frontier Center, The University of Texas at Austin（德克萨斯大学奥斯汀分校宇宙前沿中心）
- International Centre for Radio Astronomy Research, University of Western Australia（西澳大利亚大学国际射电天文研究中心）
- Research School of Astronomy and Astrophysics, Australian National University（澳大利亚国立大学天体物理学研究学院）
- Centro de Astrobiología (CAB), CSIC-INTA（西班牙国家航空航天技术研究所/西班牙国家研究委员会天体生物学中心）
- Leiden Observatory, Leiden University（莱顿大学莱顿天文台）
- Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）
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