IGRINS 高转动振动H2观测揭示的光离解区物理条件
Physical conditions in PDRs revealed by IGRINS ro-vibrational H2 observations
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中文总结 AI 辅助
本研究通过IGRINS高分辨光谱观测五个光离解区的H2发射线，结合默东PDR模型，成功约束了热压力和FUV场强度，并揭示了新形成H2分子的能量分布特征。
中文摘要 AI 辅助
我们将使用IGRINS光谱仪获得的5个光离解区（PDRs：S140、IC63、马头星云、NGC 2023和猎户座棒）的高转动振动H2观测数据，与使用默东PDR代码生成的PDR模型进行比较，以估算物理条件并约束支配PDR的物理和化学过程。我们使用了新近进行流量定标和消光校正的IGRINS H2观测数据，覆盖1.45-2.45微米波段，分辨率达45000，并通过简单的卡方最小化方法以及一种稳健方法（即贝叶斯反演结合先进MCMC技术进行后验探索）来调整默东PDR模型。PDR模型基于来自Pollux数据库的理论恒星光谱，为每个PDR使用了特定的入射远紫外（FUV）光谱。默东PDR代码能够在两倍因子内重现超过85%的观测到的H2转动振动谱线强度。我们发现：（1）对入射FUV场进行真实建模（无论是在几何形状还是光谱形状方面）以及（2）纳入H2高振动能级碰撞退激发速率的最新数据，是取得这一成功的关键。研究发现，H2转动振动发射线能够对热压力和入射FUV场强度G0提供良好的约束，尽管在大多数PDR中仍存在不可忽略的剩余简并性。额外的约束条件，例如从ALMA或JWST观测中导出的PDR空间尺度，能够消除这种简并性。对于低激发PDR，观测证据表明，在尘埃表面新形成的H2分子具有相对较低的转动能量和较高的振动能量，这与H2表面形成的理论和实验研究预测一致。
英文摘要
We compare H2 high ro-vibrational observations of 5 PDRs (S140, IC63, Horsehead Nebula, NGC 2023 and Orion Bar) obtained with the IGRINS spectrograph to PDR models produced with the Meudon PDR code, in order to estimate the physical conditions and to constrain the physical and chemical processes that govern PDRs. We use newly flux-calibrated and extinction-corrected IGRINS H2 observations covering the 1.45-2.45 um range at a resolution of 45000, and adjust Meudon PDR models using both a simple chi2 minimization approach and a robust method using Bayesian inversion followed by posterior exploration via an advanced MCMC technique. The PDR models use specific incident FUV spectra for each PDRs based on theoretical stellar spectra from the Pollux database. The Meudon PDR code is able to reproduce more than 85% of the observed H2 ro-vibrational line intensities within a factor of two. We find that (1) a realistic modeling of the incident FUV field (both in term of geometry and of spectral shape) and (2) the inclusion of recent data on collisional de-excitation rates for high vibrational levels of H2 are key to this success. H2 ro-vibrational emission lines are found to provide good constraints on both the thermal pressure and the incident FUV field strength, G0, although with a non-negligible remaining degeneracy in most PDRs. Additional constraints, such as the spatial scales of the PDR derived from ALMA or JWST observations, are found to be able to lift this degeneracy. For low excitation PDRs, the observations provide evidence that nascent H2 molecules formed on grains have relatively low rotational energy and high vibrational energy, as predicted by theoretical and experimental studies of the surface formation of H2.
发表机构
- Observatoire de Paris, PSL Research University（巴黎天文台，PSL研究大学）
- Instituto de Física Fundamental (CSIC)（基础物理研究所（西班牙高等科学研究委员会））
- Queen Mary University of London（伦敦玛丽女王大学）
- University of Texas at Austin（德克萨斯大学奥斯汀分校）
- Université Paris Cité（巴黎西岱大学）
- Université Paris-Saclay（巴黎萨克雷大学）
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