Nobuyuki Sakai D3, SOKENDAI, Mitaka（supervisor : Mareki Honma）
The first astrometry result of the Perseus arm beyond a Galactic longitude l of ~ 190 deg with VERA
Contexts. Currently, VERA and VLBA have been conducting kpc-scales astrometry to make a 3D map of the Milky Way Galaxy.
AIms. We aim to expand previous astrometry coverage of the Perseus arm from a Galactic longitude l of ~ 190 deg to that of ~ 240 deg.
This is crucial to accurately understand large scale structure of the Perseus arm.
Methods. We carried out nine-epochs VERA astrometry observations toward massive star-forming region IRAS 07427-2400 (l = 240.3 deg, b = 0.1 deg, Vlsr = 68.0 km/s) between January 20, 2012 and September 16, 2013.
Results. The measured parallactic distance is 5.18 +0.79/-0.59 kpc, which places the source in the 3rd Galactic quadrant of the Perseus arm.
Discussions. A combination of our astrometry result and previous ones reveal that the pitch angle of the Perseus arm is constant (i = 17.7 +/- 1.8 deg) in 94.60 deg < l < 240.32 deg, although the pitch angle is changed significantly (i = 11.5 +/- 1.3 deg) in 43.17 deg < l < 94.60 deg. The difference indicates that bifurcation or spur as seen in external disk galaxies may occur in 43.17 deg < l < 94.60 deg for the Perseus arm. [Speaker 2] Shino Nagisa D2, SOKENDAI, Mitaka（supervisor : Mareki Honma） [Title] Methanol maser observation of massive star formation region IRAS 18089-1732 [Abstract] The formation scenario of massive star is not yet fully understand. Methanol maser is regarded as the signpost of the formation process of the massive star. Particular, the 44GHz methanol maser is associated with an outflow, and it is said that the 6.7GHz methanol maser is associated with an accretion disk. If this is true, 44GHz methanol maser is expected to be distributed perpendicularly with respect to rotating disk. Detecting (or rejecting) this will play a major role in understanding the scenario of massive star formation. In order to test this, we observed 6.7GHz methanol maser using JVN and obtained space distribution map. We also analyzed the VLA archive data of the 44GHz methanol maser. We were able to get the space distribution map of the 44GHz methanol maser and the 6.7GHz methanol maser of IRAS18089-1732. We argue about each emission position from the result.
The first astrometry result of the Perseus arm beyond a Galactic longitude l of ~ 190 deg with VERA etc.