Jun Li, 军 李, Bingqiu Chen, 丙秋 陈, Biwei Jiang, 碧沩 姜, He Zhao, 赫 赵, Botao Jiang, 博韬 江, Xi Chen and 曦 陈
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引用次数: 0
摘要
致密分子云核中星际尘埃的消光曲线对于了解尘埃特性,特别是粒度分布和成分至关重要。我们利用英国红外深空巡天(UKIRT Infrared Deep Sky Survey)和斯皮策太空望远镜(Spitzer Space Telescope)提供的深近红外和中红外测光数据,研究了附近四个孤立分子云核--L429、L483、L673和L1165--在1.2-8.0 μm波长范围内的红外消光规律。这些观测探测到了前所未有的消光深度,在这些致密云核中达到了 AV ∼ 40-60 mag。我们通过拟合(K - λ)与(H - K)的颜色-颜色图,得出了颜色-消光比 E(K - λ)/E(H - K),然后用它们来计算消光定律 Aλ/AK。我们的分析表明,所有四个云核的红外消光曲线都非常相似,而且异常平坦,是迄今为止文献报道的最明显的平坦曲线。这种平坦性与大尘粒的存在是一致的,表明在致密环境中尘粒的生长非常明显。有趣的是,我们的发现与 Hensley 和 Draine 提出的弥漫星际环境 Astrodust 模型非常吻合。稠密内核观测结果与弥漫介质模型之间的这种一致性,凸显了尘埃演化的复杂性,以及进一步研究不同星际环境中尘埃特性的过程的必要性。
The Flattest Infrared Extinction Curve in Four Isolated Dense Molecular Cloud Cores
The extinction curve of interstellar dust in the dense molecular cloud cores is crucial for understanding dust properties, particularly size distribution and composition. We investigate the infrared extinction law in four nearby isolated molecular cloud cores—L429, L483, L673, and L1165—across the 1.2–8.0 μm wavelength range, using deep near-infrared and mid-infrared photometric data from UKIRT Infrared Deep Sky Survey and Spitzer Space Telescope. These observations probe an unprecedented extinction depth, reaching AV ∼ 40–60 mag in these dense cloud cores. We derive color-excess ratios E(K − λ)/E(H − K) by fitting color–color diagrams of (K − λ) versus (H − K), which are subsequently used to calculate the extinction law Aλ/AK. Our analysis reveals remarkably similar and exceptionally flat infrared extinction curves for all four cloud cores, exhibiting the most pronounced flattening reported in the literature to date. This flatness is consistent with the presence of large dust grains, suggesting significant grain growth in dense environments. Intriguingly, our findings align closely with the Astrodust model for a diffuse interstellar environment proposed by Hensley and Draine. This agreement between dense core observations and a diffuse medium model highlights the complexity of dust evolution and the need for further investigation into the processes governing dust properties in different interstellar environments.