The First Very Long Baseline Interferometry Image of 44 GHz Methanol Maser with the KVN and VERA Array (KaVA)
Abstract
We have carried out the first very long baseline interferometry (VLBI) imaging of 44 GHz class I methanol maser (7_{0}-6_{1}A^{+}) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151-1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds x 1.5 milliarcseconds (mas). These features are detected at a limited number of baselines within the length of shorter than approximately 650 km corresponding to 100 Mlambda in the uv-coverage. The central velocity and the velocity width of the 44 GHz methanol maser are consistent with those of the quiescent gas rather than the outflow traced by the SiO thermal line. The minimum component size among the maser features is ~ 5 mas x 2 mas, which corresponds to the linear size of ~ 15 AU x 6 AU assuming a distance of 3 kpc. The brightness temperatures of these features range from ~ 3.5 x 10^{8} to 1.0 x 10^{10} K, which are higher than estimated lower limit from a previous Very Large Array observation with the highest spatial resolution of ~ 50 mas. The 44 GHz class I methanol maser in IRAS 18151-1208 is found to be associated with the MM2 core, which is thought to be less evolved than another millimeter core MM1 associated with the 6.7 GHz class II methanol maser.
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Cite
@article{arxiv.1406.2086,
title = {The First Very Long Baseline Interferometry Image of 44 GHz Methanol Maser with the KVN and VERA Array (KaVA)},
author = {Naoko Matsumoto and Tomoya Hirota and Koichiro Sugiyama and Kee-Tae Kim and Mikyoung Kim and Do-Young Byun and Taehyun Jung and James O. Chibueze and Mareki Honma and Osamu Kameya and Jongsoo Kim and A-Ran Lyo and Kazuhito Motogi and Chungsik Oh and Nagisa Shino and Kazuyoshi Sunada and Jaehan Bae and Hyunsoo Chung and Moon-Hee Chung and Se-Hyung Cho and Myoung-Hee Han and Seog-Tae Han and Jung-Wook Hwang and Do-Heung Je and Takaaki Jike and Dong-Kyu Jung and Jin-seung Jung and Ji-hyun Kang and Jiman Kang and Yong-Woo Kang and Yukitoshi Kan-ya and Noriyuki Kawaguchi and Bong Gyu Kim and Jaeheon Kim and Hyo Ryoung Kim and Hyun-Goo Kim and Hideyuki Kobayashi and Yusuke Kono and Tomoharu Kurayama and Changhoon Lee and Jeong Ae Lee and Jeewon Lee and Jung-Won Lee and Sang Hyun Lee and Sang-Sung Lee and Young Chol Minh and Atsushi Miyazaki and Se-Jin Oh and Tomoaki Oyama and Sun-youp Park and Duk-Gyoo Roh and Tetsuo Sasao and Satoko Sawada-Satoh and Katsunori M. Shibata and Bong Won Sohn and Min-Gyu Song and Yoshiaki Tamura and Kiyoaki Wajima and Seog-Oh Wi and Jae-Hwan Yeom and Young Joo Yun},
journal= {arXiv preprint arXiv:1406.2086},
year = {2014}
}
Comments
19 pages, 3 figures