标题： 前主序Herbig星的中红外光谱：水线未探测到的解释 显示英文标题

标题： Mid-IR spectra of Pre-Main Sequence Herbig stars: an explanation for the non-detections of water lines

摘要： Herbig 星周围的盘中水线的中红外探测率约为5%，而围绕TTau型星的盘中的探测率约为50%。 这一差异的原因尚不清楚。 在这项研究中，我们希望找到一种解释，在中红外波段低质量与高质量前主序星（PMS）之间检测率不同的原因。 我们运行了盘模型，恒星参数调整到光谱类型B9到M2之间，使用辐射热化学盘建模代码ProDiMo。 我们在分辨率下生成了卷积光谱 斯皮策红外仪器（IRS）、詹姆斯韦伯太空望远镜（JWST）中红外仪器（MIRI）和甚大望远镜（VLT）可见近红外光谱仪（VISIR）。 我们应用了从典型斯皮策光谱推导出的随机噪声，以便直接与观测结果进行比较。 中红外水线的强度与中心恒星的光度直接相关。 我们探索了一个标准盘模型周围的小参数空间，考虑了尘埃-气体质量比、盘气体质量、尘埃沉降混合系数、翘曲指数、尘埃最大尺寸以及尺寸幂律分布指数。 模型表明，有可能抑制水发射，然而，当前的观测对于大多数探索的参数来说还不足以探测盘中的中红外线。 光谱中的噪声存在，加上高连续通量（噪声水平与连续通量成正比），是Herbig星未被探测到的最可能解释。 分辨率为大于20000的中红外光谱需要用来研究原行星盘中的水。 例如内隙、气固比、尘埃大小和分布、内盘标高，这些Herbig星和TTau型星盘结构上的内在差异能够解释Herbig星周围盘中较低的水探测率。 显示英文摘要

摘要： The mid-IR detection rate of water lines in disks around Herbig stars disks is about 5\%, while it is around 50\% for disks around TTauri stars. The reason for this is still unclear. In this study, we want to find an explanation for the different detection rates between low mass and high mass pre-main-sequence stars (PMSs) in the mid-IR regime. We run disk models with stellar parameters adjusted to spectral types B9 through M2, using the radiation thermo-chemical disk modeling code ProDiMo. We produce convolved spectra at the resolution of Spitzer IRS, JWST MIRI and VLT VISIR spectrographs. We apply random noise derived from typical Spitzer spectra for a direct comparison with observations. The strength of the mid-IR water lines correlates directly with the luminosity of the central star. We explored a small parameter space around a standard disk model, considering dust-to-gas mass ratio, disk gas mass, mixing coefficient for dust settling, flaring index, dust maximum size and size power law distribution index. The models show that it is possible to suppress the water emission, however, current observations are not sensitive enough to detect mid-IR lines in disks for most of the explored parameters. The presence of noise in the spectra, combined with the high continuum flux (noise level is proportional to the continuum flux), is the most likely explanation for the non detections towards Herbig stars. Mid-IR spectra with resolution higher than 20000 are needed to investigate water in protoplanetary disks. Intrinsic differences in disk structure, e.g. inner gaps, gas-to-dust ratio, dust size and distribution, and inner disk scale height, between Herbig and TTauri star disks are able to explain a lower water detection rate in disks around Herbig stars.