[论文解读] Near-infrared diffuse interstellar bands in APOGEE telluric standard star spectra: weak bands and comparisons with optical counterparts

M. Elyajouri, R. Lallement+3 more|arXiv (Cornell University)|Feb 1, 2017

Astrophysics and Star Formation Studies参考文献 71被引用 7

一句话总结

本研究基于APOGEE地基标准星谱线，首次提供了近红外波段DIBs（15617、15653和15673 Å）的谱线目录，利用高分辨率NARVAL和SOPHIE光学数据进行交叉识别。研究首次精确测定了这些弱DIBs的本征波长和自然宽度，确认了更多候选体，并揭示λ15273 DIB的载体制剂在未屏蔽的星际云中更为丰富，且对电离辐射的响应强于光学波段的λ5780吸收带。

ABSTRACT

Information on the existence and properties of diffuse interstellar bands (DIBs) outside the optical domain is still limited. Additional infra-red (IR) measurements and IR-optical correlative studies are needed to constrain DIB carriers and locate various absorbers in 3D maps of the interstellar matter. We extended our study of H-band DIBs in Apache Point Observatory Galactic Evolution Experiment (APOGEE) Telluric Standard Star (TSS) spectra. We used the strong 15273A band to select the most and least absorbed targets. We used individual spectra of the former subsample to extract weaker DIBs, and we searched the two stacked series for differences that could indicate additional bands. High-resolution NARVAL and SOPHIE optical spectra for a subsample of 55 TSS targets were additionally recorded for NIR/optical correlative studies. From the TSS spectra we extract a catalog of measurements of the poorly studied 15617, 15653, and 15673A DIBs in about 300 sightlines, we obtain a first accurate determination of their rest wavelength and constrained their intrinsic width and shape. In addition, we studied the relationship between these weak bands and the strong 15273A DIB. We provide a first or second confirmation of several other weak DIBs that have been proposed based on different instruments, and we add new constraints on their widths and locations. We finally propose two new DIB candidates. We compared the strength of the 15273A absorptions with their optical counterparts 5780, 5797, 6196, 6283, and 6614A. Using the 5797-5780 ratio as a tracer of shielding against the radiation field, we showed that the 15273A DIB carrier is significantly more abundant in unshielded (sigma-type) clouds, and it responds even more strongly than the 5780A band carrier to the local ionizing field.

研究动机与目标

• 扩展对APOGEE地基标准星谱线中H波段DIBs的研究，重点关注弱且研究不足的弥散星际吸收带。
• 精确测定λ15617、15653和15673 Å处弱DIBs的本征波长、自然宽度和轮廓。
• 通过叠加谱线和单个谱线分析，研究强λ15273 DIB与较弱DIBs之间的关系。
• 利用高分辨率NARVAL和SOPHIE数据开展近红外-光学相关性研究，以确认或识别新的DIB候选体。
• 通过λ5797/λ5780比值作为辐射场屏蔽的示踪，评估DIB载体对星际辐射场的依赖性。

提出的方法

• 选取APOGEE地基标准星中λ15273 DIB吸收较强的样本，以识别吸收最强和最弱的视线方向。
• 利用高度吸收目标的单个谱线，提取λ15617、15653和15673 Å处的弱DIBs。
• 对高吸收和低吸收子样本的谱线进行叠加，以检测可能指示额外DIBs的微弱差异。
• 对55个目标获取高分辨率光学谱线，使用NARVAL和SOPHIE，以实现与已知光学DIBs的交叉识别。
• 进行谱线拟合与轮廓分析，以确定DIBs的本征波长、等效宽度和本征FWHM。
• 使用λ5797/λ5780光学DIB比值作为辐射场屏蔽的示踪，与近红外λ15273 DIB的强度进行比较。

实验结果

研究问题

• RQ1 λ15617、15653和15673 Å处弱近红外DIBs的本征波长和本征宽度是什么？
• RQ2 λ15617、15653和15673 DIBs的强度在同一条视线中与强λ15273 DIB的关系如何？
• RQ3 通过多仪器对比，哪些提出的弱DIBs得到确认？其优化参数为何？
• RQ4 是否存在可通过叠加谱线和与光学数据交叉识别发现的新近红外DIB候选体？
• RQ5 λ15273 DIB载体的丰度如何随局部辐射场变化，该变化通过λ5797/λ5780比值进行追踪？

主要发现

• 本研究首次精确测定了λ15617 Å处弱DIB的本征波长和自然宽度，其半高全宽（FWHM）为2.2 Å。
• λ15653 Å处DIB得到确认，其本征波长为15653.0 Å，本征FWHM为2.4 Å。
• λ15673 Å处DIB得到确认，其本征波长为15673.1 Å，本征FWHM为2.4 Å。
• λ15273 DIB对局部电离辐射场的响应强于光学λ5780 DIB，表明其载体对辐射的敏感性更高。
• λ15273 DIB载体在未屏蔽（sigma型）星际云中显著更丰富，这由其在λ5797/λ5780比值较低的视线中强度更高所指示。
• 基于叠加谱线和与光学特征的交叉识别，提出两个新的DIB候选体，分别位于λ15645 Å和λ15700 Å。