发表机构
Centro de Astrobiología (CAB), CSIC-INTA; Institute of Astrophysics, Foundation for Research and Technology–Hellas (FORTH); Leiden Observatory, Leiden University; Department of Astronomy & Astrophysics, University of California San Diego; Instituto de Estudios Astrofícos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales; Millenium Nucleus for Galaxies (MINGAL); INAF Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（天体生物学中心（CAB），西班牙国家航空航天技术研究所/西班牙国家研究委员会; 希腊研究与技术基金会天体物理研究所; 莱顿大学莱顿天文台; 加州大学圣地亚哥分校天文与天体物理系; 迭戈帕托莱斯大学工程与科学学院天体物理研究所; 星系千年核心（MINGAL）; 博洛尼亚空间天体物理学与科学国家研究院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
PAHSPECS项目利用JWST/MIRI首次对宇宙正午主序星系进行PAH光谱巡天，探测多个PAH特征，发现测光可准确推断PAH光度但需IFU光谱研究比值变化，并揭示中性与电离PAH尺寸分布的差异性变化。
AI 中文摘要
人们认为，与近邻星系相比，高红移星系中星际介质（ISM）的物理条件存在巨大差异。多环芳烃（PAHs）是ISM的关键组成成分，在光致离解区域中调节气体的加热和冷却过程。然而，在z~1-2（宇宙正午）的主序（MS）星系中，PAHs尚未被探索，这限制了我们对于ISM热平衡和化学平衡的认识。我们介绍了PAH光谱巡天（PAHSPECS）JWST项目，这是首个针对z~1处MS星系中3.3、6.2、7.7、8.6和11.3微米PAH特征的MIRI/MRS巡天。五个目标天体来自HUDF中深度ALMA CO和连续谱通量限样本。我们在所有星系中探测到了6.2、7.7和11.3微米PAH特征，而3.3微米特征仅在两个星系中探测到。对宽带中红外测光数据的谱能量分布（SED）拟合，能够以约25%的精度恢复从MRS光谱分解中得出的6.2和7.7微米PAH光度。然而，3.3和11.3微米特征被高估了约50%（最高达3-5倍）。对最延展源ASPECS-6的空间分辨成图显示，7.7微米PAH对MIRI F1500W通量的贡献存在变化，这表明虽然测光可以准确推断PAH光度，但研究PAH比值变化和表征星系尘埃性质需要积分场单元（IFU）光谱。来自测光SED建模的PAH占尘埃总质量的比例与从光谱测量的L_PAH/L_IR比值大致相符，但相关性不如模型预测的那样紧密。平均而言，PAHSPECS星系相对于近邻尘埃发光系统表现出6.2微米等效宽度过剩，但3.3微米等效宽度低于近邻系统，与z~1-3处的高质量星暴星系相似。这指向宇宙正午星系中中性PAH和电离PAH的尺寸分布存在差异性变化。
英文摘要
The physical conditions of the interstellar medium (ISM) are thought to differ greatly at high redshifts compared to local galaxies. Polycyclic aromatic hydrocarbons (PAHs) are key ISM constituents, mediating the heating and cooling of gas in photo-dissociation regions. However, PAHs are unexplored in main-sequence (MS) galaxies at z~1-2 (cosmic noon), limiting our view of the ISM's thermal and chemical balance. We present the PAH Spectroscopic Survey (PAHSPECS) JWST program, the first MIRI/MRS survey of the 3.3, 6.2, 7.7, 8.6 and 11.3$μ$m PAH features in MS galaxies at z~1. The five targets come from the deep ALMA CO and continuum flux-limited sample in the HUDF. We detect the 6.2, 7.7 and 11.3$μ$m PAHs in all galaxies, and the 3.3$μ$m feature in only two. Spectral energy distribution (SED) fitting to broad-band mid-IR photometry recovers the 6.2 and 7.7$μ$m PAH luminosities derived from spectral decomposition of the MRS spectra to within ~25% accuracy. However, the 3.3 and 11.3$μ$m features are overestimated by ~50% (up to 3-5x). Spatially resolved maps of ASPECS-6, the most extended source, show variations of the 7.7$μ$m PAH contribution to the MIRI F1500W flux, suggesting that while photometry can infer PAH luminosity accurately, IFU spectroscopy is necessary to study variations in PAH ratios and characterize galaxy dust properties. The PAH fraction of the total dust mass from photometric SED modeling roughly agrees with the $L_{\rm PAH}/L_{\rm IR}$ ratio measured from spectroscopy, but the correlation is not as tight as models predict. On average, PAHSPECS galaxies show an excess in 6.2$μ$m equivalent width relative to nearby dusty luminous systems, but lower 3.3$μ$m equivalent widths than local systems, similar to higher-mass starbursts at z~1-3. This points to differential changes in the size distributions of neutral and ionized PAHs in cosmic noon galaxies.
CommentsSubmitted to A&A
