AI 中文总结
本研究利用JWST NIRCam成像，提出经验方法分离PAH相关发射，发现近邻星系3.3微米PAH特征变化由金属丰度和辐射场光谱驱动，为PAH特性诊断提供关键依据。
AI 中文摘要
我们利用詹姆斯·韦布空间望远镜（JWST）近红外相机（NIRCam）成像，研究近邻星系中的3.3微米多环芳烃（PAH）特征。对3.3微米特征的NIRCam观测正成为研究星际介质（ISM）结构及约0.1角秒分辨率下尘埃条件的有力工具，这类观测图像需要精确扣除基础连续谱发射。我们提出一种经验方法，利用F300M和F360M滤光片对连续谱进行扣除，以分离F335M滤光片中与PAH相关的发射。我们发现，与PAH相关发射的F335M/F300M与F360M/F300M颜色之比的斜率，依赖于局部ISM特性，其中对恒星形成率密度的依赖最强。在活跃恒星形成区域，这些波段捕获的较弱发射特征相对于主3.3微米特征受到抑制。我们发现3.3/7.7和3.3/11.3微米比值的变化趋势，表明PAH的大小、电荷以及不同辐射场光谱的加热作用发生了改变。我们发现这两个波段比值均随金属丰度增加而降低，将其归因于低金属丰度下PAH种群向更小尺寸转变。与光学电离气体线比值及尘埃模型的对比显示，星际辐射场光谱的变化会影响PAH特征比值。该分析支持观测到的PAH波段比值随金属丰度变化的抑制增长形成场景，并强调在将这些波段比值用作PAH特性诊断时，考虑局部辐射场特征和气相金属丰度的重要性。
英文摘要
We use JWST NIRCam imaging to investigate the 3.3 $μ$m polycyclic aromatic hydrocarbon (PAH) feature in nearby galaxies. NIRCam observations of the 3.3 $μ$m feature are emerging as a powerful tool for studying the structure of the interstellar medium (ISM) and the conditions of the dust at ~0".1 resolution. These maps require accurate subtraction of the underlying continuum emission. We present an empirical method to isolate the PAH-correlated emission in the F335M filter using the F300M and F360M filters for continuum subtraction. We find that the slope of the F335M/F300M versus F360M/F300M colors for PAH-correlated emission shows a dependence on local ISM properties, with the strongest dependence on specific star formation rate. Weaker emission features captured by these bands appear suppressed relative to the main 3.3 $μ$m feature in regions of active star formation. We find trends in the 3.3/7.7 and 3.3/11.3 $μ$m ratios that suggest changes in PAH size, charge, and heating by a varying radiation field spectrum. We find decreases in both band ratios with increasing metallicity, which we attribute to a shift to smaller PAH populations at low metallicity. Comparison to optical ionized gas line ratios and dust models show that variations in the interstellar radiation field spectrum influence the PAH feature ratios. This analysis supports inhibited growth formation scenarios for the observed PAH band ratio trends with metallicity and emphasizes the importance of considering the local radiation field characteristics and gas-phase metallicity when using these band ratios as PAH property diagnostics.
Comments39 pages, 24 figures, 3 tables; accepted for publication in ApJ
