AI 中文总结
研究AB Aur行星形成盘中的方位分子变化，通过NOEMA 1.2毫米观测发现化学多样性，用转动图分析等方法探究其成因，揭示环境吸积和行星形成共同影响盘化学方位变化及行星组成。
AI 中文摘要
后期吸积事件正成为盘演化的重要驱动力。这种吸积在分子线和散射光中表现为丝状飘带，扰乱盘结构，但其化学后果仍未明确。我们展示了对AB Aur的NOEMA 1.2毫米观测，这是一个有结构的年轻赫比格盘，有正在进行的吸积和行星形成迹象。我们检测到方位化学多样性：在北部盘靠近推测的飘带 - 盘相互作用区域SO发射增强，而C₂H在相对的南侧达到峰值；CS形成近乎轴对称的环。HCN和HCO⁺在尘埃环中的尘埃连续体过密度附近达到峰值。转动图分析表明北部SO的转动温度和柱密度较高，而CS保持轴对称且转动温度较低，这表明这些物种探测不同的盘层。对于C₂H，温度变化可能有影响但不能完全解释不对称性。HCO⁺/H¹³CO⁺线比值表明HCO⁺在分子环上光学厚度大，而腔内升高的比值表明气相¹²C/¹³C增强，与同位素选择性光解离一致。与化学模型比较支持气相C/O比值接近或高于1，在C₂H明亮区域有效C/O更高。我们讨论了化学不对称的两个起源：（i）吸积引起的含O冰的加热和解吸增强了SO并降低了飘带撞击点附近的气相C/O，（ii）行星驱动的子结构和局部加热或增强的紫外线辐射促进了南部盘中富含烃的化学过程。这些结果突出了环境吸积和行星形成可共同在盘化学中 imprint方位变化，对形成行星的组成有潜在影响。
英文摘要
Late infall episodes are emerging as an important driver of disk evolution. Observed as filamentary streamers in molecular lines and scattered light, such accretion perturbs disk structures, yet its chemical consequences remain unconstrained. We present NOEMA 1.2 mm observations of AB Aur, a structured young Herbig disk showing evidence for ongoing infall and planet formation. We detect azimuthal chemical diversity: SO emission is enhanced in the northern disk near the inferred streamer-disk interaction region, while C$_2$H peaks on the opposite southern side; CS forms a nearly axisymmetric ring. HCN and HCO$^+$ peak near the dust continuum overdensity in the dust ring. Rotational diagram analyses show higher SO rotational temperatures and column densities in the north, whereas CS remains axisymmetric with lower rotational temperatures, suggesting that the species probe different disk layers. For C$_2$H, temperature variations may contribute to but cannot fully explain the asymmetries. The HCO$^+$/H$^{13}$CO$^+$ line ratio indicates that HCO$^+$ is optically thick across the molecular ring, while the elevated ratio inside the cavity suggests enhanced gas-phase $^{12}$C/$^{13}$C, consistent with isotope-selective photodissociation. Comparison with chemical models favors gas-phase C/O ratios near or above unity, with higher effective C/O in the C$_2$H-bright sector. We discuss two origins for the chemical asymmetries: (i) infall-induced heating and desorption of O-bearing ices enhance SO and lower gas-phase C/O near the streamer's impact site, and (ii) planet-driven substructures and localized heating or enhanced UV irradiation promote hydrocarbon-rich chemistry in the southern disk. These results highlight that environmental accretion and planet formation can jointly imprint azimuthal variations in disk chemistry, with potential impacts on forming planets' compositions.
Comments17 pages, 15 figures, 2 tables in the main text, 4 appendices, Accepted for publication in A&A
