AI 中文总结
本研究利用JWST在日心距离1.33天文单位处观测过近日点的彗星C/2022 E3（ZTF），测绘其挥发物与尘埃组成，分析分子分布特征并与其他彗星对比。
AI 中文摘要
我们报告了一项利用詹姆斯·韦伯空间望远镜（JWST）对奥尔特云彗星C/2022 E3（ZTF）的彗星挥发物分子发射进行的观测调查，该观测于2023年2月28日至3月1日世界时开展，此时彗星的日心距离（rH）为1.33天文单位（au）。本次测量涵盖了H₂O、HCN、CH₃OH、C₂H₆、CH₄、CO、CO₂、¹³CO₂和OCS等分子，采样了C/2022 E3过近日点后的分子化学过程，同时还检测到了一组近至中红外的OH（ prompt emission，即时发射）跃迁。本研究提供了所有检测到的分子以彗核为中心的光谱、除C₂H₆、HCN和OH之外所有分子的柱密度和转动温度随距彗核距离变化的空间-光谱图，以及共同测量的连续谱图。所有被测绘分子的柱密度和转动温度的空间分布均呈各向异性；不过，H₂O的分布与其他分子不同。从这些图中推导得出的H₂O的正-仲比（OPR）和¹²CO₂/¹³CO₂比值的 coma-averaged（彗发平均）值，分别与3的统计平衡值和89的陆地值一致。亚微米级尘埃颗粒的模拟质量分数主要由无定形碳（占56%）构成，其次是无定形镁铁辉石（28%）、结晶橄榄石（10%）和无定形镁铁橄榄石（5%），结晶质量分数为0.2385(0.0008)。我们将C/2022 E3（ZTF）的挥发物和尘埃组成与迄今已测量的彗星（包括JWST观测过的彗星）进行了比较。
英文摘要
We report a survey of molecular emission from cometary volatiles using the James Webb Space Telescope (JWST) toward Oort cloud comet C/2022 E3 (ZTF) carried out on UT 2023 February 28 and March 1 at a heliocentric distance (rH) of 1.33 au. These measurements of H2O, HCN, CH3OH, C2H6, CH4, CO, CO2, 13CO2, and OCS sampled post-perihelion molecular chemistry in C/2022 E3. A suite of near to mid-infrared OH (prompt emission) transitions were also detected. This work presents nucleus-centered spectra for all detected species, spatial-spectral maps of column density and rotational temperature as a function of distance from the nucleus for all except C2H6, HCN, and OH, and maps of co-measured continuum. The spatial distributions of both quantities were anisotropic for all mapped molecules; however, H2O showed distributions distinct from the remaining species. Coma-averaged values of the ortho-to-para ratio (OPR) for H2O and the 12CO2/13CO2 ratio derived from these maps were consistent with the statistical equilibrium value of 3 and the terrestrial value of 89, respectively. The modeled mass fraction of the sub-micron dust grains is dominated by amorphous carbon (56%) followed by amorphous Mg:Fe pyroxene (28%), crystalline olivine (10%), and amorphous Mg:Fe olivine (5%) with a crystalline mass fraction of 0.2385(0.0008). We compare the volatile and dust composition of C/2022 E3 (ZTF) against comets measured to date, including those surveyed by JWST.
Comments20 pages, 15 figures, 4 tables
