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首页> 外文期刊>Astronomy and astrophysics >Full two-dimensional radiative transfer modelling of the transitional disk LkCa 15
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Full two-dimensional radiative transfer modelling of the transitional disk LkCa 15

机译：过渡盘LkCa 15的完整二维辐射传递建模

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Context. With the legacy of Spitzer and current advances in(sub)mm astronomy, a considerable number of so-called ``transitional''disks has been identified which are believed to contain gaps or havedevelopped large inner holes, some filled with dust. This may indicatethat complex geometries may be a key feature in disk evolution that hasto be understood and modelled correctly. The disk around LkCa15 is such a disk, with a large gap ranging from 5-46AU, as identified by Espaillat et al. (2007, ApJ, 670, L135) using 1+1Dradiative transfer modelling. To fit the spectral energy distribution(SED), they propose two possible scenarios for the inner(<5AU) disk - optically thick or optically thin - and onescenario for the outer disk. Aims. We use the gapped disk of LkCa 15 as a case in point toillustrate the importance of 2D radiative transfer in transitionaldisks by showing how the vertical dust distribution in dust-filledinner holes determines not only the radial optical depth but also theouter disk geometry. Methods. We use MCMax, a 2D radiative transfer code with aself-consistent vertical density and temperature structure, to modelthe SED of LkCa 15. Results. We identify two possible geometries for the inner andouter disk that are both different from those in Espaillat et al.(2007, ApJ, 670, L135). An inner disk in hydrostatic equilibriumreprocesses enough starlight to fit the near infrared flux, but alsocasts a shadow on the inner rim of the outer disk. This requires theouter disk scale height to be high enough to rise out of the shadow. Anoptically thin inner disk does not cast such a shadow, and the SED canbe fitted with a smaller outer disk scale height. For the dust in theinner regions to become optically thin however, the scale height wouldhave to be so much higher than its hydrostatic equilibrium value thatit effectively becomes a dust shell. It is currently unclear if aphysical mechanism exists which could provide for such a configuration.Conclusions. We find that the radial optical depth of dustwithin the inner hole of LkCa 15 is controlled by its verticaldistribution. If it turns optically thick, the outer disk scale heightmust be increased to raise the outer disk out of the inner disk'sshadow. Key words: stars: pre-main sequence - stars: individual: LkCa 15 - protoplanetary disks - radiative transfer - circumstellar matter
机译：上下文。随着Spitzer的遗留和（亚）毫米天文学的最新发展，已经确定了许多所谓的``过渡''磁盘，这些磁盘被认为存在间隙或形成了较大的内孔，其中一些充满了灰尘。这可能表明复杂的几何形状可能是磁盘演变中的关键特征，必须正确理解和建模。 Espaillat等人发现，LkCa15周围的磁盘就是这样的磁盘，其间隙介于5-46AU之间。 （2007，ApJ，670，L135）使用1 + 1Dradiative传输建模。为了适合光谱能量分布（SED），他们为内层（<5AU）磁盘提出了两种可能的方案-光学厚度或光学厚度-和外层磁盘的两种方案。目的我们以LkCa 15的间隙盘为例，通过显示充满尘埃的内孔中的垂直尘埃分布不仅决定径向光学深度而且决定了外盘的几何形状，来说明过渡盘二维辐射传递的重要性。方法。我们使用MCMax（具有自身一致的垂直密度和温度结构的2D辐射传递代码）对LkCa 15的SED进行建模。我们确定了内盘和外盘的两种可能的几何形状，它们与Espaillat等人（2007，ApJ，670，L135）中的不同。处于静水平衡状态的内圆盘可再加工足够的星光以适合近红外通量，但也会在外圆盘的内缘上投射阴影。这要求外盘刻度尺高度必须足够高以从阴影中升起。光学上较薄的内部磁盘不会产生阴影，因此SED可以安装较小的外部磁盘刻度高度。然而，为了使内部区域的灰尘变得光学上稀薄，水垢高度必须比其静水平衡值高得多，以至于它实际上变成了灰尘壳。目前尚不清楚是否存在可以提供这种配置的物理机制。我们发现，LkCa 15内孔中灰尘的径向光学深度受其垂直分布的控制。如果从光学角度变厚，则必须增加外盘刻度尺的高度，以将外盘从内盘的阴影中抬起。关键词：恒星：主前序-恒星：单个：LkCa 15-原行星盘-辐射传递-绕星物质

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