Fundamental Parameters of the Milky Way Galaxy Based on VLBI astrometry
Abstract
We present analyses to determine the fundamental parameters of the Galaxy based on VLBI astrometry of 52 Galactic maser sources obtained with VERA, VLBA and EVN. We model the Galaxy's structure with a set of parameters including the Galaxy center distance R_0, the angular rotation velocity at the LSR Omega_0, mean peculiar motion of the sources with respect to Galactic rotation (U_src, V_src, W_src), rotation-curve shape index, and the V component of the Solar peculiar motions V_sun. Based on a Markov chain Monte Carlo method, we find that the Galaxy center distance is constrained at a 5% level to be R_0 = 8.05 +/- 0.45 kpc, where the error bar includes both statistical and systematic errors. We also find that the two components of the source peculiar motion U_src and W_src are fairly small compared to the Galactic rotation velocity, being U_src = 1.0 +/- 1.5 km/s and W_src = -1.4 +/- 1.2 km/s. Also, the rotation curve shape is found to be basically flat between Galacto-centric radii of 4 and 13 kpc. On the other hand, we find a linear relation between V_src and V_sun as V_src = V_sun -19 (+/- 2) km/s, suggesting that the value of V_src is fully dependent on the adopted value of V_sun. Regarding the rotation speed in the vicinity of the Sun, we also find a strong correlation between Omega_0 and V_sun. We find that the angular velocity of the Sun, Omega_sun, which is defined as Omega_sun = Omega_0 + V_sun/R_0, can be well constrained with the best estimate of Omega_sun = 31.09 +/- 0.78 km/s/kpc. This corresponds to Theta_0 = 238 +/- 14 km/s if one adopts the above value of R_0 and recent determination of V_sun ~ 12 km/s.
Keywords
Cite
@article{arxiv.1211.3843,
title = {Fundamental Parameters of the Milky Way Galaxy Based on VLBI astrometry},
author = {Mareki Honma and Takumi Nagayama and Kazuma Ando and Takeshi Bushimata and Yoon Kyung Choi and Toshihiro Handa and Tomoya Hirota and Hiroshi Imai and Takaaki Jike and Mi Kyoung Kim and Osamu Kameya and Noriyuki Kawaguchi and Hideyuki Kobayashi and Tomoharu Kurayama and Seisuke Kuji and Naoko Matsumoto and Seiji Manabe and Takeshi Miyaji and Kazuhito Motogi and Akiharu Nakagawa and Hiroyuki Nakanishi and Notaro Niinuma and Chung Sik Oh and Toshihiro Omodaka and Tomoaki Oyama and Nobuyuki Sakai and Katsuhisa Sato and Mayumi Sato and Katsunori Shibata and Satoshi Shiozaki and Kazuyoshi Sunada and Yoshiaki Tamura and Yuji Ueno and Aya Yamauchi},
journal= {arXiv preprint arXiv:1211.3843},
year = {2015}
}
Comments
14 pages, 6 figures, PASJ in press