论文标题
II组Herbig磁盘中的二分法：Alma Gas Disk高度测量结果显示出垂直延伸的大型阴影和紧凑的扁平磁盘
A dichotomy in group II Herbig disks: ALMA gas disk height measurements show both shadowed large vertically extended disks and compact flat disks
论文作者
论文摘要
Herbig星可以根据光谱能量分布中的Far-Ir多余的形状分为第一组和II组。这种分离可能是进化的，并且与这些磁盘的垂直结构有关。我们旨在确定Herbig磁盘的排放高度，并比较两组的垂直范围。 Alma带6对12CO发射线的观测值和八个Herbig磁盘（四个I组和四个II组源）的空间分辨率以12CO发射线的形式通过其他作品中开发的几何方法来确定来自通道图的发射高度。我们发现，所有组磁盘的高度与半径比至少为0.25，并且对于三个磁盘，气体发射曲线可以追溯到200-500 au。 II组磁盘分为MWC 480和HD 163296，它们的发射高度轮廓与I组磁盘相似，AK SCO和HD 142666非常平坦（不超过10个AU的高度）和更紧凑的（大小<200 au）。当宿主恒星的亮度被解释时，亮度温度在磁盘之间没有差异。我们的发现与以前的工作一致，表明I组磁盘已垂直扩展，并且II组磁盘是大型且自我阴影或紧凑的。 MWC 480和HD 163296均可能是I组磁盘的前体，我们现在在形成腔内可以辐射磁盘的外部部位之前看到的。非常平坦的磁盘AK SCO和HD 142666可能是由于这些磁盘的高龄（〜20而不是<10 Myr）而引起的。这些垂直结构上的这些巨大差异并未反映在这些磁盘的光谱分布中。在较高的空间和速度分辨率下，更深入的观察对于进一步表征了Herbig子组。
Herbig stars can be classified into group I and group II depending on the shape of the far-IR excess from the spectral energy distribution. This separation may be evolutionary and related to the vertical structure of these disks. We aim to determine the emission height of Herbig disks and compare the resulting vertical extent of both groups. ALMA Band 6 observations of 12CO emission lines at sufficient velocity and spatial resolution of eight Herbig disks (four group I and four group II sources) are used to determine the emission heights from the channel maps via geometrical methods developed in other works. We find that all group I disks are vertically extended with a height to radius ratio of at least 0.25, and for three of the disks the gas emission profile can be traced out to 200-500 au. The group II disks are divided between MWC 480 and HD 163296 which have similar emission height profiles as the group I disks, and AK Sco and HD 142666 which are very flat (not exceeding a height of 10 au) and more compact (<200 au in size). The brightness temperatures show no differences between the disks when the luminosity of the host star is accounted for. Our findings agree with previous work suggesting that group I disks are vertically extended and that group II disks are either large and self-shadowed or compact. Both MWC 480 and HD 163296 could be precursors of group I disks, which we see now before a cavity has formed that would allow irradiation of the outer parts of the disk. The very flat disks AK Sco and HD 142666 could be due to significant settling because of the advanced age of these disks (~20 instead of <10 Myr). These large differences in vertical structures are not reflected in the spectral energy distributions of these disks. More and deeper observations at higher spatial and velocity resolution are necessary to further characterize the Herbig sub-groups.
