Astrophys. J., 804, 143 (2015/May-2)
High-resolution 25 M imaging of the disks around Herbig Ae/Be stars.
HONDA M., MAASKANT K., OKAMOTO Y.K., KATAZA H., YAMASHITA T., MIYATA T., SAKO S., FUJIYOSHI T., SAKON I., FUJIWARA H., KAMIZUKA T., MULDERS G.D., LOPEZ-RODRIGUEZ E., PACKHAM C. and ONAKA T.
Abstract (from CDS):
We imaged circumstellar disks around 22 Herbig Ae/Be stars at 25 µm using Subaru/COMICS and Gemini/T-ReCS. Our sample consists of an equal number of objects from each of the two categories defined by Meeus et al.; 11 group I (flaring disk) and II (flat disk) sources. We find that group I sources tend to show more extended emission than group II sources. Previous studies have shown that the continuous disk is difficult to resolve with 8 m class telescopes in the Q band due to the strong emission from the unresolved innermost region of the disk. This indicates that the resolved Q-band sources require a hole or gap 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, but 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 idea 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 into the mid-plane of the protoplanetary disk. However, considering the growing evidence for the presence of a hole or gap 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.
circumstellar matter - protoplanetary disks - stars: pre-main sequence
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