AI 中文总结
研究通过构建三维模型估计原行星盘冷却时间尺度，进而推断尘埃表面密度和粒径，以HD 142527盘为例，发现其北部阴影区域冷却时间尺度及最大粒径，还满足垂直剪切不稳定性条件，为约束尘埃粒径提供有效工具，可用于其他过渡盘。
AI 中文摘要
行星形成始于年轻恒星周围原行星盘中的尘埃增长和星子形成。为理解这些过程，从盘观测估计尘埃粒径至关重要。本研究基于冷却时间尺度估计开发了一种约束粒径的新方法。该方法适用于具有倾斜内盘在外盘上投下阴影的过渡盘，利用近红外散射光图像构建盘表面三维模型并与亚毫米尘埃连续体图比较，估计冷却时间尺度，再构建解析模型推断尘埃表面密度和粒径。将此方法应用于HD 142527原行星盘，发现盘北部阴影区域冷却时间尺度约为轨道周期的百分之几，与观测一致的最大粒径约为0.1 - 1毫米，还满足垂直剪切不稳定性所需条件。研究表明估计冷却时间尺度是约束尘埃粒径的有效工具，该方法可普遍应用于其他有内盘诱导阴影的过渡盘。
英文摘要
Planet formation begins with dust growth and planetesimal formation within protoplanetary disks surrounding young stars. To understand these processes, it is essential to estimate dust grain sizes from disk observations. In this study, we develop a new method to constrain grain size based on the estimation of cooling timescales. Our approach applies to transitional disks that possess an inclined inner disk casting shadows on the outer disk, whose temperature variations serve as a tracer of dust properties. By constructing a three-dimensional model of the disk surface using near-infrared scattering light images and comparing it with submillimeter dust continuum maps, we estimate the spatial offset between the irradiated and shadowed regions to derive the cooling timescale. We then build an analytic model that calculates the cooling timescale at the dust thermal emission height with an assumed turbulent diffusion intensity to infer the dust surface density and dust grain size. Applying this method to the protoplanetary disk around HD~142527, we find that the disk's northern shadowed region cools on a timescale of a few percent of the orbital period and that the maximum grain size consistent with the observations is approximately 0.1-1 mm. We also find that the conditions required for the vertical shear instability, which needs a short cooling timescale, are satisfied, allowing turbulence with an intensity consistent with near-infrared observations. This study demonstrates that estimating cooling timescales is an effective tool for constraining dust grain size. Our approach can be generally applied to other transition disks with inner-disk-induced shadows.
Comments25 pages, 21 figures, 2 tables, submitted to PASJ
