AI 中文总结
该研究基于JWST/MIRI的8个宽带数据，揭示M51星系中红外发射与气体柱密度、恒星形成的关联，发现PAHs偏向示踪气体、尘埃连续谱反映恒星形成，且关联存在波长依赖偏移。
AI 中文摘要
利用JWST/MIRI对M51星系的8个宽带成像数据，我们研究了多环芳烃（PAHs）和尘埃连续谱的中红外发射，与分别由CO(1-0)、HI和Pa-α示踪的分子气体、原子气体及电离气体之间的关联。在分子气体主导的区域，PAH主导的滤光片（F560W、F770W、F1130W、F1280W）在40pc尺度上与CO(1-0)呈现近线性关联，表明PAHs与气体混合良好且辐射场强度相对稳定；而F1500W、F1800W和F2100W等尘埃连续谱主导的滤光片与CO(1-0)的关联斜率更平缓，反映了高辐射场强度恒星形成区的贡献，这一点也通过F2100W与Pa-α的近线性标度关系得到印证。PAH主导波段未显示与Pa-α的线性趋势，可能是由于其在电离区被破坏；F1000W在与CO(1-0)和Pa-α的关联中表现与PAH波段类似。通过将中红外发射经验分解为气体相关和恒星形成相关分量的建模显示，PAH主导滤光片从两类分量获得的贡献相当，而与Pa-α模板相关的相对贡献随波长增加，在F2100W中达到约75%。这些结果表明，中红外可同时示踪气体柱密度和恒星形成，但关联驱动因素存在系统性波长依赖偏移：PAHs更偏向示踪气体，尘埃连续谱则反映恒星形成。最后，在440pc分辨率下结合HI和H₂，我们发现Σ_{HI+H₂}与PAH主导滤光片之间存在紧密线性关系；尽管观测覆盖区域多为H₂主导区，但HI区域也呈现类似结果，表明PAHs也与原子气体混合良好。
英文摘要
Using JWST/MIRI imaging of M51 in eight broadband filters, we investigate correlations of mid-infrared emission from polycyclic aromatic hydrocarbons (PAHs) and dust continuum with molecular, atomic, and ionized gas traced by CO(1-0), HI, and Pa-alpha, respectively. In molecular gas-dominated regions, PAH-dominated filters (F560W, F770W, F1130W, F1280W) exhibit near-linear correlations with CO(1-0) at 40 pc scale, indicating that PAHs are well-mixed with gas and experience relatively constant radiation field intensities. The F1500W, F1800W, and F2100W dust continuum-dominated filters show shallower slopes with CO(1-0), reflecting contributions from star-forming regions with high radiation field intensities. This is reinforced by the near-linear scaling between F2100W and Pa-alpha. PAH-dominated bands do not show this linear trend with Pa-alpha, likely due to their destruction in ionized regions. F1000W behaves similarly to PAH bands in its correlations with CO(1-0) and Pa-alpha. Modeling mid-infrared emission with an empirical decomposition into gas- and star-formation-associated components shows that PAH-dominated filters receive comparable contributions from both, while the relative contribution associated with the Pa-alpha template increases toward longer wavelengths, reaching $\sim$75% in F2100W. These results demonstrate that mid-infrared simultaneously traces the gas column and star formation, but with a systematic wavelength-dependent shift in what drives the correlations: PAHs being more gas-tracing and dust-continuum reflecting star formation. Lastly, considering both HI and H$_2$ at 440 pc resolution, we find a tight, linear relation between $Σ_{HI+H_2}$ and PAH-dominated filters. Although most of our coverage is in H$_2$-dominated regions, we note similar observations with HI, suggesting that PAHs are also well-mixed with atomic gas.
Comments(Accepted for publication in ApJ)
