East Asian VLBI Network astrometry toward the extreme outer Galaxy: Kinematic distance with the proper motion of G034.84−00.95
Year: 2022
Type: article
Abstract: We aim to reveal the structure and kinematics of the Outer Scutum–Centaurus (OSC) arm located on the far side of the Milky Way through very long baseline interferometry (VLBI) astrometry using KaVA, which is composed of KVN (the Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We report the proper motion of a 22 GHz H2O maser source, which is associated with the star-forming region G034.84−00.95, to be (μαcos δ, μδ) = (−1.61 ± 0.18, −4.29 ± 0.16) mas yr−1 in equatorial coordinates (J2000.0). We estimate the 2D kinematic distance to the source to be 18.6 ± 1.0 kpc, which is derived from the variance weighted average of kinematic distances with local standard of rest velocity and the galactic-longitude component of the measured proper motion. Our result places the source in the OSC arm and implies that G034.84−00.95 is moving away from the Galactic plane with a vertical velocity of −38 ± 16 km s−1. Since the H i supershell GS033+06−49 is located at a kinematic distance roughly equal to that of G034.84−00.95, it is expected that gas circulation occurs between the outer Galactic disk around G034.84−00.95 with a Galactocentric distance of $12.8^{+1.0}_{-0.9}\:$kpc and the halo. We evaluate possible origins of the fast vertical motion of G034.84−00.95, which are (1) supernova explosions and (2) cloud collisions with the Galactic disk. However, neither of these possibilities are matched with the results of VLBI astrometry or the spatial distributions of H ii regions and H i gas.
DOI: 10.1093/pasj/psac102
Authors: Nobuyuki Sakai, Bo Zhang, Shuangjing Xu, Daisuke Sakai, Yoshiaki Tamura, Takaaki Jike, Taehyun Jung, Chungsik Oh, Jeong-Sook Kim, Noriyuki Kawaguchi, Hiroshi Imai, Wu Jiang, Lang Cui, Soon-Wook Kim, Pengfei Jiang, Tomoharu Kurayama, Jeong Ae Lee, Kazuya Hachisuka, Dong-Kyu Jung, Bo Xia, Guanghui Li, Mareki Honma, Kee-Tae Kim, Zhi-Qiang Shen, Na Wang
Institutions: Korea Astronomy and Space Science Institute, National Astronomical Research Institute of Thailand, Chinese Academy of Sciences, Shanghai Astronomical Observatory, National Astronomical Observatory of Japan, Ulsan National Institute of Science and Technology, Kagoshima University, Xinjiang Astronomical Observatory, Teikyo University of Science, Korea University of Science and Technology
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4313263233