Geumsook Park(Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea, Research Institute of Basic Sciences, Seoul National University, Seoul 08826, Republic of Korea)
Bon-Chul Koo(Department of Physics and Astronomy, Seoul National University, Seoul 08861, Republic of Korea, Research Institute of Basic Sciences, Seoul National University, Seoul 08826, Republic of Korea)
Kee-Tae Kim(Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea)
Bruce Elmegreen(IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, USA)