对超新星1987A的JWST NIRSpec观测——从内部抛射物到反向激波
JWST NIRSpec observations of Supernova 1987A -- from the inner ejecta to the reverse shock
AI总结：
利用JWST NIRSpec在1–5 μm的空间分辨光谱，研究绘制SN 1987A内部铁抛射物与反向激波的三维结构，并用光谱模型揭示分子氢激发、金属线成因及赤道环高温气体。
摘要：
我们展示了JWST NIRSpec积分场单元对邻近超新星（SN）1987A观测的初步结果。这些观测首次在1–5 μm波段提供了抛射物与赤道环（ER）的空间分辨光谱。我们构建了来自内部抛射物的[Fe I] 1.443 μm谱线以及来自反向激波（RS）的He I 1.083 μm谱线的三维发射率图，其中前者用于探测爆炸几何结构，后者用于追踪星周介质结构。我们还提出了一个抛射物积分光谱模型。[Fe I]三维图揭示了高度不对称的形态，类似破碎的偶极子，由速度约2300 km/s的两个大团块主导。我们还发现富铁内部抛射物已开始与反向激波相互作用的证据。由He I谱线追踪的反向激波面从赤道环稍内侧延伸至赤道环两侧的更高纬度，半张角约45度，形成泡状结构。抛射物的光谱模型使我们能够识别许多发射线，包括大量H₂谱线。我们发现H₂最有可能由远紫外辐射激发，而金属线比值与低温抛射物中碰撞激发和复合的共同作用相符。我们还在赤道环中发现若干高电离日冕线，要求温度高于2×10^6 K。
英文摘要：
We present initial results from JWST NIRSpec integral field unit observations of the nearby Supernova (SN) 1987A. The observations provide the first spatially-resolved spectroscopy of the ejecta and equatorial ring (ER) over the 1-5 μm range. We construct 3D emissivity maps of the [Fe I] 1.443 μm line from the inner ejecta and the He I 1.083 μm line from the reverse shock (RS), where the former probes the explosion geometry and the latter traces the structure of the circumstellar medium. We also present a model for the integrated spectrum of the ejecta. The [Fe I] 3D map reveals a highly-asymmetric morphology resembling a broken dipole, dominated by two large clumps with velocities of ~2300 km/s. We also find evidence that the Fe-rich inner ejecta have started to interact with the RS. The RS surface traced by the He I line extends from just inside the ER to higher latitudes on both sides of the ER with a half-opening angle ~45 degrees, forming a bubble-like structure. The spectral model for the ejecta allows us to identify the many emission lines, including numerous H_2 lines. We find that the H_2 is most likely excited by far-UV emission, while the metal lines ratios are consistent with a combination of collisional excitation and recombination in the low-temperature ejecta. We also find several high-ionization coronal lines from the ER, requiring a temperature > 2 \times 10^6 K.
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