Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1B011


Sugiyama, Koichiro (Yamaguchi University)
Fujisawa, Kenta (Yamaguchi University)
Hachisuka, Kazuya (SHAO)
Yonekura, Yoshinori (Ibaraki University)
Motogi, Kazuhito (Yamaguchi University)
Sawada-Satoh, Satoko (NAOJ)
Matsumoto, Naoko (NAOJ)
Furukawa, Naoko (Ibaraki University)
Hirano, Daiki (Yamaguchi University)
Saito, Yu (Ibaraki University)
Shen, Zhiqiang (SHAO)
Honma, Mareki (NAOJ)
Hirota, Tomoya (NAOJ)
Murata, Yasuhiro (ISAS/JAXA)
Doi, Akihiro (ISAS/JAXA)
Niinuma, Kotaro (Yamaguchi University)
Dodson, Richard (KASI)
Rioja, Maria (ICRAR)
Ellingsen, Simon (University of Tasmania)
Chen, Xi (SHAO)
Kim, Kee-Tae (KASI)
Ogawa, Hideo (Osaka Prefecture University)

We have started a VLBI monitor project of the 6.7 GHz methanol maser sources by using the Japanese VLBI Network (JVN) and the East-Asian VLBI Network (EAVN). The 6.7 GHz methanol maser emission can be one of the best probe to obtain 3-dimensional (3-D) velocity information, particularly on an accretion disk around forming high-mass protostars. The systematic VLBI survey monitor can provide us a chance to understand the evolution of the accretion disk, which is one of the basic issues in the high-mass star formation. Our VLBI monitor project for the 6.7 GHz methanol masers has been started since August 2010 toward 36 sources, which are at mainly southern hemisphere, brighter than 65 Jy in total flux densities, and no previous VLBI observations (including two previous VLBI sources for verification of imaging capabilities). In this presentation, we will show a result of the JVN/EAVN imaging survey for all of 36 target sources obtained in 2010-2012 as an initial result of this project. In this imaging survey, spatial distributions of the methanol maser spots in 35 sources were obtained, in which 33 sources provide new VLBI images. The new images increase the VLBI imaged sample of the 6.7 GHz methanol maser by 1.5 times compared to that so far. The spatial morphology was classified into five categories on the basis of the criteria used in the previous VLBI observations (Bartkiewicz et al. 2009), including elliptical, arched, and linear morphology which could be the best candidates associated with the disk (Fujisawa et al. to be submitted). The VLBI imaging survey result was compared to spatial distributions observed with the Australia Telescope Compact Array (ATCA). The ATCA observations provided us the spatial distribution without a missing flux, and solved ambiguities for some sources classified into the complex spatial morphology on the basis of the VLBI survey. We also present an initial result for a detection of relative proper motions and 3-D velocity information in the elliptical methanol maser sources, G006.79-00.25. The detected motions suggest that the methanol masers showing the elliptical morphology can trace the rotating disk.

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