AI 中文总结
该研究利用SPHEREx光谱绘制四个原恒星核的水冰图，通过核辉光构建冰吸收图，分析冰吸收情况。虽模型无法解释最致密核中心吸收降低现象，但证明核辉光光谱可追踪冰密度和成分，是探测致密核中冰的新手段。
AI 中文摘要
我们利用SPHEREx光谱，首次给出了四个原恒星核中3μm H₂O冰吸收特征的、基于核辉光的空间分辨图谱。冰是分子云致密核的关键成分，在年轻恒星周围行星形成化学过程中起核心作用。但空间分辨丰度研究有限，通常依赖分布不均的背景恒星视线。我们利用SPHEREx全天空分光能力，通过散射银河辐射（核辉光）照射致密核来构建具有均匀空间分辨率的冰吸收图。为验证概念，分析了四个附近（约140秒差距）原恒星核——L1544、CrA 151、L260和L1512中空间变化的H₂O冰吸收情况。两个核符合冰吸收在中心达到峰值的预期空间趋势，但两个最致密的核在最内部区域的观测冰吸收出现惊人下降。为解释吸收图，构建了受散射照射的邦诺-埃伯特球的分析和模拟模型，研究不同几何构型、冰质量分数和冰成分空间差异的影响，均无法解释中心吸收降低的情况，这表明在最致密的原恒星区域存在未解释的物理或化学效应。我们的模拟进一步表明，从核辉光获得的光谱能有力追踪空间变化的冰密度和成分，确立了SPHEREx散射光光谱作为致密核中冰的强大新探测手段。
英文摘要
We present the first coreshine-derived, spatially-resolved maps of the 3 $μ$m H$_2$O ice absorption feature in four prestellar cores, using SPHEREx spectra. Ices are a key component of dense cores in molecular clouds, playing a central role in the chemistry of planet formation around young stars. However, spatially resolved abundance studies remain limited, typically relying on unevenly distributed background star sightlines. Here, we take advantage of the all-sky spectrophotometric capabilities of SPHEREx to construct ice absorption maps with uniform spatial resolution using the illumination of dense cores by scattered Galactic radiation, or coreshine. To demonstrate proof of concept, we analyse the spatially varying H$_2$O ice absorption in four nearby (~140 pc) prestellar cores - L1544, CrA 151, L260 and L1512. Two cores follow the expected spatial trend of ice absorption peaking at the centre, but the two densest cores show a surprising drop in observed ice absorption in the innermost regions. To interpret the absorption maps, we construct analytical and simulated models of a Bonnor-Ebert sphere illuminated by scattering. We study the effects of different geometric configurations, ice mass fractions, and spatial differences in ice composition. None of these can explain the reduced central absorption, pointing to an unexplained physical or chemical effect operating in the densest prestellar regions. Our simulations further show that spectra derived from coreshine provide a robust tracer of spatially varying ice density and composition, establishing SPHEREx scattered-light spectroscopy as a powerful new probe of ice in dense cores.
Comments21 pages including Appendix, 10 figures, submitted to AAS Journals. Ice map data (and code) at https://github.com/tamojeetroychowdhury/SPHEREx-Prestellar-Cores
