[论文解读] Towards DIB mapping in galaxies beyond 100 Mpc. A radial profile of the $λ$5780.5 diffuse interstellar band in AM 1353-272 B

A. Monreal‐Ibero, Peter M. Weilbacher+6 more|GoeScholar The Publication Server of the Georg-August-Universität Göttingen (Georg-August-Universität Göttingen)|Feb 23, 2015

Astrophysics and Star Formation Studies参考文献 32被引用 10

一句话总结

本研究首次利用MUSE积分场光谱仪，对本超集团以外的星系——AM 1353-272 B——中的弥散星际带（DIB）λ5780.5进行了空间分辨映射。通过将13.5 kpc²范围内568个空间分辨光谱叠加，结果表明DIB等效宽度随径向距离减小，且与星际消光相关，首次在外部旋涡星系中证实了全球性的DIB-消光关系。

ABSTRACT

Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of stars viewed through one or several clouds of Interstellar Medium (ISM). Research of DIBs outside the Milky Way is currently very limited. Specifically spatially resolved investigations of DIBs outside of the Local Group is, to our knowledge, inexistent. Here, we explore the capability of the high sensitivity Integral Field Spectrograph, MUSE, as a tool to map diffuse interstellar bands at distances larger than 100 Mpc. We use MUSE commissioning data for AM 1353-272 B, the member with highest extinction of the "The Dentist's Chair", an interacting system of two spiral galaxies. High signal-to-noise spectra were created by co-adding the signal of many spatial elements distributed in a geometry of concentric elliptical half-rings. We derived decreasing radial profiles for the equivalent width of the $λ$5780.5 DIB both in the receding and approaching side of the companion galaxy up to distances of $\sim$4.6 kpc from the center of the galaxy. Likewise, interstellar extinction, as derived from the Halpha/Hbeta line ratio displays a similar trend, with decreasing values towards the external parts. This translates into an intrinsic correlation between the strength of the DIB and the extinction within AM 1353-272 B consistent with the current existing global trend between these quantities when using measurements for both Galactic and extragalactic sight lines. Mapping of DIB strength in the Local Universe as up to now only done for the Milky Way seems feasible. This offers a new approach to study the relationship between DIBs and other characteristics and species of the ISM in different conditions as those found in our Galaxy to the use of galaxies in the Local Group and/or single sightlines towards supernovae, quasars and galaxies outside the Local Group.

研究动机与目标

• 展示利用高灵敏度积分场光谱仪在100 Mpc以外的星系中实现空间分辨DIB映射的可行性。
• 研究λ5780.5 DIB在AM 1353-272 B中的空间分布，该星系为距离159 Mpc的低光度、高消光旋涡星系。
• 检验已知的DIB强度与星际消光之间的相关性是否适用于与银河系条件不同的外部星系。
• 探索MUSE及类似仪器在未来大范围本地宇宙DIB映射中的潜力。
• 为超越单一线视向测量的DIB-ISM关系研究提供新的方法论框架。

提出的方法

• 在MUSE仪器调试运行期间获取了AM 1353-272 B的积分场光谱，视场为1×1角分，光谱分辨率R≈2800。
• 通过将分布在星系内同心椭圆半环上的568个空间单元信号叠加，生成高信噪比光谱。
• 在星系六个不同区域测量了λ5780.5 DIB的等效宽度，覆盖范围达中心约4.6 kpc。
• 利用Hα/Hβ线对比率计算星际消光，获得星系内各区域的E(B-V)值。
• 对比DIB等效宽度与消光的径向分布，评估其在外部星系中的相关性。
• 整理并对比本研究与现有银河系及河外视线的DIB-消光数据，评估其与全局趋势的一致性。

实验结果

研究问题

• RQ1 能否利用积分场光谱仪在本超集团以外的星系中对λ5780.5弥散星际带实现空间分辨与映射？
• RQ2 在AM 1353-272 B中，DIB的强度是否如在银河系中所见，与星系盘面的星际消光呈相关性？
• RQ3 AM 1353-272 B中的DIB-消光关系与其它星系（包括本超集团内星系及大、小麦哲伦云）中的关系相比如何？
• RQ4 环境因素（如金属丰度、辐射场及恒星形成活动）在多大程度上调节外部星系中DIB-消光相关性？
• RQ5 高灵敏度仪器（如MUSE）是否能够实现在本地宇宙中的2D DIB映射，从而为研究DIB载体开辟新途径？

主要发现

• λ5780.5 DIB的等效宽度在AM 1353-272 B中从星系中心向外径向减小，其分布曲线在朝向和退向侧均延伸至约4.6 kpc的径向距离。
• 由Hα/Hβ线对比率推导出的星际消光也表现出类似的径向减小趋势，表明星系外区的尘埃含量较低。
• 在AM 1353-272 B中，DIB等效宽度与消光（E(B-V)）之间存在显著相关性，且在测量不确定度范围内比值恒定。
• AM 1353-272 B中的DIB-消光关系与银河系及M31中观测到的全局趋势一致，尤其在考虑旋涡星系的解析研究时更为明显。
• AM 1353-272 B的数据将DIB-消光关系延伸至更高的等效宽度和E(B-V)值，与其它盘状星系中观察到的趋势一致。
• 本研究证实，利用当前高灵敏度积分场光谱仪（如MUSE）在本超集团以外的星系中实现2D DIB映射是可行的。