MIPSGAL 24 μm observations of Galactic planetary nebulae
MIPSGAL 24 μm observations of Galactic planetary nebulae
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MIPSGAL 24 μm 银河系行星状星云观测
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
R. A. Márquez
中科院分区：
文献类型：
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作者：
J. P. Phillips;R. A. Márquez
我们获得了 224 个行星状星云 (PNe) 的 24 μm 成像、轮廓和通量，这些行星状星云位于使用斯皮策多波段成像光度计 (MIPSGAL) 进行的银河巡天范围内。值得注意的是，大多数具有扩展 24 μm 发射的 PNe 也具有圆形形态，这表明发射源自位于渐近巨星分支 (AGB) 质量损失区域内的冷颗粒。发现这些光晕中的某些具有表面亮度下降，这可能与 PNe 祖细胞内长期不变的质量损失一致。相比之下，8.0 μm 包络被检测到距原子核的距离更小，并且表面亮度下降速度更快；这种现象可能是由于外部光解离区域 (PDR) 内多环芳烃 (PAH) 的激发变化而引起的。我们将 24 μm 通量与之前发表的研究中的通量进行了比较，这似乎表明许多先前的通量被低估了；这种差异可能意味着以前的孔径尺寸太小。我们还将 24 μm 通量与使用红外阵列相机 (IRAC) 拍摄的较短中红外 (MIR) 波长的测量结果结合起来。这些用于研究 PNe 在 IRAC-MIPSGAL 颜色平面内的定位。 [8.0]-[24] 和 [5.8]-[24] 颜色被发现很大，并且延伸到各自的范围 3.4-8.7 mag 和 5.4-10.3 mag；这些指数只有在多种机制对通量产生影响时才能解释，包括 PAH 带、冷尘连续体和各种离子跃迁。这些和其他成分也会影响光源的形态，并导致轮廓宽度随波长变化。
We have obtained 24 μm imaging, profiles and fluxes for 224 planetary nebulae (PNe) lying within the limits of the Galactic survey undertaken with the Multiband Imaging Photometer for Spitzer (MIPSGAL). It is noted that most of the PNe having extended 24 μm emission also possess circular morphologies, suggesting that the emission derives from cool grains located within the Asymptotic Giant Branch (AGB) mass-loss regimes. Certain of these haloes are found to have a surface brightness fall-off which may be consistent with secularly invariant mass loss within the PNe progenitors. By contrast, the 8.0 μm envelopes are detected out to smaller distances from the nuclei, and have a steeper rate of surface brightness fall-off ; a phenomenon which may arise from changes in the excitation of polycyclic aromatic hydrocarbons (PAHs) within external photo-dissociation regimes (PDRs). Our 24 μm fluxes are compared to those in previously published studies, and this appears to indicate that many of the prior fluxes have been underestimated; a disparity may imply that previous aperture sizes were too small. We have also combined our 24 μm fluxes with measures at shorter mid-infrared (MIR) wavelengths, taken with the Infrared Array Camera (IRAC). These are used to investigate the positioning of PNe within the IRAC-MIPSGAL colour planes. The [8.0]-[24] and [5.8]-[24] colours are found to be large, and extend over the respective ranges 3.4-8.7 mag, and 5.4-10.3 mag; indices which are only explainable where a broad range of mechanisms contribute to the fluxes, including PAH bands, cool dust continua and a variety of ionic transitions. These and other components also affect the morphologies of the sources, and lead to wavelength-dependent changes in the widths of the profiles.