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arXiv 1407.4579astro-ph.SR
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Herschel分辨碎片谱中的圆盘半径和颗粒尺寸

Disk Radii and Grain Sizes in Herschel-Resolved Debris Disks

Nicole Pawellek, Alexander V. Krivov, Jonathan P. Marshall, Benjamin Montesinos, Péter Ábrahám, Attila Moór, Geoffrey Bryden, Carlos Eiroa

摘要:

碎片盘的半径及其尘埃颗粒的大小是这些系统中形成机制和物理过程的痕迹。我们使用34个碎片磁盘的样本空间解决各种赫歇尔程序来约束他们。虽然我们模拟的磁盘与温暖和寒冷的组件,我们专注于我们的分析只对寒冷的外磁盘,即柯伊伯带的类似物。从解析图像中得出的碎片盘半径显示出很大的分散度,但与恒星亮度没有显着的趋势,这反对冰线在设定碎片盘尺寸方面发挥主导作用。固定磁盘半径的推断,从解决的图像,我们的光谱能量分布模型,以确定尘埃温度和粒度分布。虽然尘埃温度系统地增加对早期的光谱类型,它的比率,在磁盘半径的黑体温度降低与恒星光度。这是由典型的颗粒尺寸增加,朝向更明亮的恒星解释的。的大小相比,辐射压力井喷限制$s_\text{blow}$,这是成比例的恒星的光度质量比,因此也增加对早期的光谱类。在G-到A-恒星的磁盘中的颗粒大小被推断为$s_\text{blow}$在所有恒星光度的几倍,与碰撞模型的碎片磁盘。以$s_\text{blow}$为单位测量的大小似乎随着光度的增加而减小,这可能暗示着盘的搅拌水平朝着更早类型的恒星增加。

英文摘要:

(Abridged) The radii of debris disks and the sizes of their dust grains are tracers of the formation mechanisms and physical processes operating in these systems. We use a sample of 34 debris disks spatially resolved in various Herschel programs to constrain them. While we modeled disks with both warm and cold components, we focus our analysis only on the cold outer disks, i.e. Kuiper-belt analogs. The disk radii derived from the resolved images reveal a large dispersion, but no significant trend with the stellar luminosity, which argues against ice lines as a dominant player in setting the debris disk sizes. Fixing the disk radii to those inferred from the resolved images, we model the spectral energy distributions to determine the dust temperatures and the grain size distributions. While the dust temperature systematically increases towards earlier spectral types, its ratio to the blackbody temperature at the disk radius decreases with the stellar luminosity. This is explained by an increase of typical grain sizes towards more luminous stars. The sizes are compared to the radiation pressure blowout limit $s_\text{blow}$ that is proportional to the stellar luminosity-to-mass ratio and thus also increases towards earlier spectral classes. The grain sizes in the disks of G- to A-stars are inferred to be several times $s_\text{blow}$ at all stellar luminosities, in agreement with collisional models of debris disks. The sizes, measured in the units of $s_\text{blow}$, appear to decrease with the luminosity, which may be suggestive of the disk's stirring level increasing towards earlier-type stars.

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