Galactic Outer Rotation Curve project with VERA

【日時】4月18日(水) 10:30~12:00
【場所】国立天文台・三鷹 中央棟(北)1階 講義室
【発表者(敬称略)】(総研大 D2 坂井 伸行・三鷹、指導教員:本間 希樹
Galactic Outer Rotation Curve project with VERA
I will talk mainly about two topics,
(1) Sakai et al. 2012 in accepted and
(2) Future prospects of our project.
The abstract of (1) is shown as below:
We report measurement of trigonometric parallax of IRAS 05168+3634 with VERA.
The parallax is 0.532 +/- 0.053 mas, corresponding to a distance of 1.88+0.21 -0.17 kpc. This result is significantly smaller than the previous distance estimate of 6 kpc based on kinematic distance. This drastic change in the source distance revises not only physical parameters of IRAS 05168+3634, but also its location of the source, placing it in the Perseus arm rather than the Outer arm. We also measure proper motions of the source. A combination of the distance and the proper motions with systemic velocity
yields rotation velocity (Θ) of 227+9-11 km s-1 at the source, assuming Θ0 = 240 km s-1. Our result combined with previous VLBI results for six sources in the Perseus arm indicates that the sources rotate systematically slower than the Galactic rotation velocity at the LSR. In fact, we show observed disk peculiar motions averaged over the seven sources in the Perseus arm as (Umean, Vmean) = (11 +/- 3, -17 +/- 3) km s-1, indicating that these seven sources are systematically moving toward the Galactic center, and lag behind the Galactic rotation.