标题： 斯皮策中红外观测七个多极行星状星云 显示英文标题

标题： Spitzer Mid-Infrared Observations of Seven Bipolar Planetary Nebulae

摘要： 我们利用斯皮策空间望远镜（SST）和墨西哥国家天文台获取的成像和光谱数据，研究了七个双极行星状星云（BPNe）的中红外（MIR）和可见结构。 结果表明，这些天体在更长的MIR波长下更为扩展，并且在5.8和8.0微米波段具有更高的表面亮度。 还注意到，5.8/4.5和8.0/4.5微米流量比随着距离源核的距离增加而增加。 所有这些趋势可能归因于环状星云光致离解区（PDRs）内的多环芳烃（PAHs）和/或温暖尘埃连续谱的发射。 相反，8.0/5.8微米流量比的相应降低可能是由于PAH发射颗粒的性质发生变化所致。 我们在NGC 2346包层中发现了可能的8.0微米环状结构，该结构位于电离包层的次要轴限制之外的区域。 对内层两个环的分析显示，尽管它们在较长的MIR波长下具有更高的表面亮度，但它们在3.6和4.5微米波段相对于底 emission 更强。 流出的主要轴上也存在点反射对称性的证据。 显示英文摘要

摘要： We have investigated the mid-infrared (MIR) and visual structures of seven bipolar planetary nebulae (BPNe), using imaging and spectroscopy acquired using the Spitzer Space Telescope (SST), and the Observatorio Astronomico Nacional in Mexico. The results show that the sources are more extended towards longer MIR wavelengths, as well as having higher levels of surface brightness in the 5.8 and 8.0 microns bands. It is also noted that the 5.8/4.5 and 8.0/4.5 microns flux ratios increase with increasing distance from the nuclei of the sources. All of these latter trends may be attributable to emission by polycyclic aromatic hydrocarbons (PAHs) and/or warm dust continua within circum-nebular photo-dissociation regions (PDRs). A corresponding decrease in the flux ratios 8.0/5.8 microns may, by contrast, arise due to changes in the properties of the PAH emitting grains. We note evidence for possible 8.0 microns ring-like structures in the envelope of NGC 2346, located in a region beyond the minor axis limits of the ionized envelope. An analysis of the inner two rings shows that whilst they have higher surface brightnesses at longer MIR wavelengths, they are relatively stronger (compared to underlying emission) at 3.6 and 4.5 microns. There is also evidence for point reflection symmetry along the major axis of the outflow.