| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2001: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2000: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Many young stars were found in OB associations by the large-scale survey of emission-line stars. It is possible that the young stars not associated with apparent molecular clouds have formed in small clouds, which are remnants of molecular material. Bright-rimmed clouds (BRCs), small molecular clouds directly associated with HII regions, are believed to be sites of ongoing star formation. However, the comparisons with previous observations of Bok globules without bright rims indicated that BRCs differ significantly in the bolometric luminosities of associated YSOs and their circumstellar dust mass. Previous studies are mainly based on the catalog of BRCs associated with IRAS point sources. We made an unbiased catalog of BRCs, and tried to perform multi-wavelength studies of them. We used the grism spectrograph to survey emission-line stars in BRCs. Several emission-line stars are found even in BRCs, which are not associated with IRAS sources. Molecular line mapping is important to estimate the physical parameters of BRCs. We observed thirty-five of BRCs in CS J=2-1 line, and twenty-four of them in optically thin H^<13>CO^+ J=1-0 line. The typical size and mass of BRCs are 0.3 pc and 10 solar masses, respectively. We found several interesting BRCs to note. For example, BRC31 consists of the aggregation of three dense clumps. The dense and clumpy tail structure is shown in BRC38, whose head part is facing towards the HII region. This tail part harbors several YSOs. In the case of BRC14, H^<13>CO^+ clumps make a dense shell around the central luminous IRAS source. This suggests the interaction between the molecular gas and the cluster forming activity. Furthermore, we challenged the NIR imaging observations of wide field of view to investigate CTTs and H2 jets from YSOs to understand the star forming history of some BRCs. Still, more discussions and follow-up works are needed to clarify the role of BRCs in star formation.
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