斯皮策小麦哲伦云巡天（S3MC）：对多环芳烃生命周期的洞察
The Spitzer Survey of the Small Magellanic Cloud (S3MC): Insights into the Life-Cycle of Polycyclic Aromatic Hydrocarbons
摘要：
我们提出的结果建模灰尘SEDs整个SMC的目的是映射在低金属含量的环境中的多环芳烃的分布。使用斯皮策巡天的SMC（S3 MC）测光从3.6-160微米以上的主要恒星形成区域的机翼和酒吧随着光谱映射从5-38微米从斯皮策光谱巡天的SMC（S4 MC）在选定的区域，我们建立模型的灰尘SED和发射光谱，以确定在整个SMC的多环芳烃尘埃的分数。我们使用重叠的光度和光谱的区域来测试从SED拟合单独确定的PAH分数的可靠性。与银河系相比，SMC中的PAH分数较低，并且可变-分子云中的分数相对较高（q_PAH~1-2%），弥漫ISM中的分数较低（<q_PAH>=0.6%）。我们使用的多环芳烃馏分在SMC的地图，以测试一些想法的生产，销毁和处理的多环芳烃在ISM。我们发现PAH分数和碳AGB星的分布，超巨星H I壳和年轻的SN遗迹的位置，或湍流的马赫数之间的相关性弱或没有。我们发现，PAH馏分与CO强度，在尘埃表面密度和分子气体表面密度的峰值，确定从160微米的排放。PAH分数是高的活跃的恒星形成的地区，其相关性与分子气体预测，但在H II地区被抑制。由于PAH馏分中的扩散ISM一般是非常低的-根据以前的工作建模的SED的SMC-和PAH馏分是相对较高的分子区域，我们建议，多环芳烃被破坏的扩散ISM的SMC和/或多环芳烃形成的分子云。我们讨论了这些意见的影响，我们的理解PAH的生命周期，特别是在低金属含量的星系。
英文摘要：
We present the results of modeling dust SEDs across the SMC with the aim of mapping the distribution of PAHs in a low-metallicity environment. Using Spitzer Survey of the SMC (S3MC) photometry from 3.6-160 um over the main star-forming regions of the Wing and Bar along with spectral mapping from 5-38 um from the Spitzer Spectroscopic Survey of the SMC (S4MC) in selected regions, we model the dust SED and emission spectrum to determine the fraction of dust in PAHs across the SMC. We use the regions of overlapping photometry and spectroscopy to test the reliability of the PAH fraction as determined from SED fits alone. The PAH fraction in the SMC is low compared to the Milky Way and variable--with relatively high fractions (q_PAH~1-2%) in molecular clouds and low fractions in the diffuse ISM (<q_PAH>=0.6%). We use the map of PAH fraction across the SMC to test a number of ideas regarding the production, destruction and processing of PAHs in the ISM. We find weak or no correlation between the PAH fraction and the distribution of carbon AGB stars, the location of supergiant H I shells and young SN remnants, or the turbulent Mach number. We find that the PAH fraction is correlated with CO intensity, peaks in the dust surface density and the molecular gas surface density as determined from 160 um emission. The PAH fraction is high in regions of active star-formation, as predicted by its correlation with molecular gas, but is suppressed in H II regions. Because the PAH fraction in the diffuse ISM is generally very low--in accordance with previous work on modeling the SED of the SMC--and the PAH fraction is relatively high in molecular regions, we suggest that PAHs are destroyed in the diffuse ISM of the SMC and/or PAHs are forming in molecular clouds. We discuss the implications of these observations for our understanding of the PAH life cycle, particularly in low-metallicity galaxies.
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