HD 144432多环内盘富铁尘埃的中红外证据
Mid-infrared evidence for iron-rich dust in the multi-ringed inner disk of HD 144432
AI总结：
本文利用VLTI多仪器红外干涉数据和新模型TGMdust研究HD 144432内盘，发现其三环结构及富铁尘埃更符合观测，提出温暖内盘中碳主要在气相而铁和硫化物为固体主要成分。
摘要：
背景。岩质行星通过固体颗粒在行星形成盘内几个天文单位区域内聚集而形成。它们的化学成分反映了行星形成时盘内以固态形式存在的物质。目标。我们旨在利用甚大望远镜干涉仪（VLTI）获取的大量红外干涉数据，结合PIONIER、GRAVITY和MATISSE观测，约束年轻恒星HD 144432内盘的结构和尘埃成分。方法。我们引入了一个新的物理盘模型TGMdust，用于对干涉数据进行成像，并拟合盘结构和尘埃成分。我们还使用GGchem进行了平衡凝聚计算。结果。我们的最佳拟合模型具有三个盘区，在0.15、1.3和4.1天文单位处具有环状结构。假设盘中约0.9天文单位和约3天文单位处的暗区是由行星打开的空隙，我们估计假想的打开空隙的行星质量约为一个木星质量。我们发现了来自内两个盘区（r<4天文单位）在λ>3微米处光学薄发射（τ<0.4）的证据。我们的硅酸盐成分拟合证实了径向矿物学梯度。为了确定负责红外连续谱发射的尘埃成分，我们探索了两种尘埃成分情况，一种是硅酸盐+铁混合物，另一种是硅酸盐+碳混合物。我们发现富铁模型对光谱能量分布提供了更好的拟合。结论。我们提出，在典型行星形成盘的温暖内部区域（r<5天文单位）中，大部分甚至全部碳处于气相，而铁和硫化铁颗粒与镁橄榄石和顽火辉石一起是固体混合物的主要成分。我们的分析表明，需要使用新的中红外仪器（如MATISSE和JWST/MIRI）对内盘尘埃进行详细研究。
英文摘要：
Context. Rocky planets form by the concentration of solid particles in the inner few au regions of planet-forming disks. Their chemical composition reflects the materials in the disk available in the solid phase at the time the planets were forming. Aims. We aim to constrain the structure and dust composition of the inner disk of the young star HD 144432, using an extensive set of infrared interferometric data taken by the Very Large Telescope Interferometer (VLTI), combining PIONIER, GRAVITY, and MATISSE observations. Methods. We introduced a new physical disk model, TGMdust, to image the interferometric data, and to fit the disk structure and dust composition. We also performed equilibrium condensation calculations with GGchem. Results. Our best-fit model has three disk zones with ring-like structures at 0.15, 1.3, and 4.1 au. Assuming that the dark regions in the disk at ~0.9 au and at ~3 au are gaps opened by planets, we estimate the masses of the putative gap-opening planets to be around a Jupiter mass. We find evidence for an optically thin emission ($τ<0.4$) from the inner two disk zones ($r<4$ au) at $λ>3\ μ$m. Our silicate compositional fits confirm radial mineralogy gradients. To identify the dust component responsible for the infrared continuum emission, we explore two cases for the dust composition, one with a silicate+iron mixture and the other with a silicate+carbon one. We find that the iron-rich model provides a better fit to the spectral energy distribution. Conclusions. We propose that in the warm inner regions ($r<5$ au) of typical planet-forming disks, most if not all carbon is in the gas phase, while iron and iron sulfide grains are major constituents of the solid mixture along with forsterite and enstatite. Our analysis demonstrates the need for detailed studies of the dust in inner disks with new mid-infrared instruments such as MATISSE and JWST/MIRI.
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