片坐 宏一

著者人数: 29名形態: カラー図版あり資料番号: AA1730027053レポート番号: JAXA-SP-17-010E

We imaged circumstellar disks around 22 Herbig Ae/Be stars at 25 μm using Subaru/COMICS and Gemini/T-ReCS. Our sample consisted of 11 group I (flaring disk) andgroup II (flat disk) sources. We found that group I sources tended to show more extended emission than group II sources. Previous studies showed that the continuous disk is hard to resolve with 8-meter-class telescopes in the Q-band due to the strong emissions from the unresolved innermost region of the disk. This indicates that Q-band resolution sources requires a hole orgap in the disk material distribution to suppress the contribution from the innermost region of the disk. As many group I sources are resolved at 25 μm, we suggest that many, not all, group I Herbig Ae/Be disks have a hole or gap and are (pre-)transitional disks. On the other hand, the unresolved nature of many group II sources at 25 μm supports the suggestion that group II disks have a continuous, flat disk geometry. It has been inferred that group I disks may evolve into group II through the settling of dust grains at the mid-plane of the proto-planetary disk. However, considering growing evidence of the presence of a hole or gaps in the disk of group I sources, such an evolutionary scenario is unlikely. The difference between groups I and II may reflect different evolutionary pathways of protoplanetary disks..原著2014 年度神奈川大学総合理学研究所共同研究助成論文

The disk around the Herbig Ae star HD169142 was imaged and resolved at 18．8 and 24．5 μm using Subaru／COMICS. We interpreted the observations using a 2D radiative transfer model and found evidence for the presence of a large gap．MIR images trace dust emits at the onset of a strong rise in the spectral energy distribution（SED）at 20 μm；therefore，they are very sensitive to the location and characteristics of the inner wall of the outer disk and its dust．We determined the location of the wall to be 23 ＋3 －5 AU from the star．An extra component of hot dust must therefore exist close to the star．We found that a hydrostatic optically thick inner disk does not produce enough flux in the NIR and an optically thin geometrically thick component was our solution to fit the SED．Considering the recent findings of gaps and holes in a number of Herbig Ae／Be group I disks，we suggest that such disk structures may be common in group I sources．Classification as group I should be considered to support the classification as a transitional disk，although improved imaging surveys are needed to support this speculation．原著 2011 年度神奈川大学総合理学研究所共同研究助成論文