Kee-Tae Kim

100-GHZ BAND TEST OBSERVATIONS OF THE KVN 21-M RADIO TELESCOPES

We carry out 100-GHz band test observations with the newly-constructed KVN 21-m radio telescopes in order to evaluate their performance. The three telescopes have similar performance parameters. The pointing accuracies are about 4 00 rms for the entire sky. The main beam sizes are about 30 00 (FWHMs), which is nearly the difiraction limit of the telescopes at the observing frequency (97 GHz). The measured aperture and main-beam e‐ciencies are about 52% and 46%, respectively, for all three telescopes. The estimated moon e‐ciency is »84% for the KVN Tamna telescope. The flrst sidelobes appear 50 00 (»1.6£FWHM) from the main beam centers and the levels are on average i14 dB.

Recent progress in Korean VLBI Network (KVN) project

Korea’s new VLBI project to construct the Korean VLBI Network (KVN) began in 2001 as a 7year project that is fully funded by Korean government. We plan to build three new high-precision radio telescopes of 21-m diameter at three sites in Korea. We will install the 2/8, 22 and 43-GHz HEMT receivers by 2008, and later we will expand the receiving frequency range up to 129 GHz for astronomical, geodetic, and space research. As for the front-end system, we are going to install multi-channel receivers with low-pass filters within a quasi-optical beam transportation plate. With this system, multi-frequency phase referencing for millimetre-wave VLBI as well as simultaneous multi-frequency observations will be carried out. Mark 5B will be used as the recording system. We have completed the design of the KVN data acquisition system of 2 Gsps sampling rate, which will use 4 data streams to meet the multi-channel requirement.

Properties of the molecular clump and the associated ultracompact H II region in the gas shell of the expanding H II region Sh 2-104

We study the physical and chemical properties of the molecular clump hosting a young stellar cluster, IRAS 20160+3636, which is believed to have formed via the “collect and collapse” process. Physical parameters of the UC Hii region associated with the embedded cluster are measured from the radio continuum observations. This source is found to be a typical Galactic UC Hii region, with a B0.5 type exciting star, if it is ionized by a single star. We derive a CN/HCN abundance ratio larger than 1 over this region, which may suggest that this clump is being affected by the UV radiation from the Hii region.

The VLBI imaging survey of the 6.7 GHz methanol masers using the JVN/EAVN

K. Sugiyama∗a, K. Fujisawaba, K. Hachisukac, Y. Yonekurad , K. Motogib, Z. -Q. Shenc, M. Honmae, T. Hirotae, S. Sawada-Satoh f , Y. Muratag, A. Doig, R. Dodsonh, M. J. Riojah, S. P. Ellingseni, K.-T. Kim j, and H. Ogawak aGraduate school of Science and Engineering, Yamaguchi University, Japan bResearch Institute for Time Studies, Yamaguchi University, Japan cShanghai Astronomical Observatory, Chinese Academy of Sciences, China dCenter for Astronomy, Ibaraki University, Japan eVERA Project, National Astronomical Observatory of Japan (NAOJ), Japan f Mizusawa VLBI Observatory, NAOJ, Japan gThe Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan hInternational Center for Radio Astronomy Research, University of Western Australia, Australia iSchool of Mathematics and Physics, University of Tasmania, Australia jKorea Astronomy and Space Science Institute, 776 Daedeokdae-ro, South Korea kDepartment of Physical Science, Osaka Prefecture University, Japan