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Toward early scientific results on AGNs: 'KAVA'(KVN and VERA array) joint AGN WG report
손봉원,이상성,Sohn, Bong Won,Kino, Motoki,Niinuma, Kotaro,Lee, Sang-Sung,Honma, Mareki,Nagai, Hiroshi,Sascha, Sascha Trippe,Jung, Taehyun 한국천문학회 2012 天文學會報 Vol.37 No.2
We report the results of KVN-VERA('KAVA'; KVN and VERA Arrary) AGN WG test observation in 2011 and 2012. The results from these commisioning years show that 'KAVA' is able to produce noble images of radio loud AGNs at 22 and 43GHz. This dedicated high frequency VLBI facility will be especially competitive for the regions where conventional low freuquency facilities see the optically thick part of synchrotron radiation. In the second part of this talk, we report the early science activities of the AGN WG. Sgr A*, Jet acceleration zone of M87, extremely young radio galaxies are the prime cadidates of the joint activities. Lastly we will stress how the phase-referencing 'KAVA' does enhance the imaging sensitivity and open new era of VLBI AGN researches.
Ricean Bias Correction in Linear Polarization Observation
손봉원 한국우주과학회 2011 Journal of Astronomy and Space Sciences Vol.28 No.4
I developed an enhanced correction method for Ricean bias which occurs in linear polarization measurement. Two known methods for Ricean bias correction are reviewed. In low signal-to-noise area, the method based on the mode of the equation gives better representation of the fractional polarization. But a caution should be given that the accurate estimation of noise level, i.e. σ of the polarized flux, is important. The maximum likelihood method is better choice for high signal-to-noise area. I suggest a hybrid method which uses the mode of the equation at the low signal-to-noise area and takes the maximum likelihood method at the high signal-to-noise area. A modified correction coefficient for the mode solution is proposed. The impact on the depolarization measure analysis is discussed.