VLBI study of water maser emission in the Seyfert 2 galaxy NGC5793. I: Imaging blueshifted emission and the parsec-scale jet

摘要: We present the first result of VLBI observations blueshifted water maser emission from type 2 Seyfert galaxy NGC5793, which we combine with new and previous continuum at 1.7, 5.0, 8.4, 15, 22 GHz. Maser was detected earlier in single-dish found to have both red- features relative systemic velocity. could image only emission, is located 3.6 pc southwest GHz peak. The originate two clusters that are separated by 0.7 milliarcsecond (0.16 pc). No compact within spot. A source showing a marginally inverted spectrum between 1.7 5.0 4.2 position. spectral turnover might be due synchrotron self-absorption caused shock jet owing collision dense gas, or it free-free absorption an ionized screen possibly inner part disk, foreground jet. The may disk. If so, would rotating opposite sense highly inclined galactic disk observed CO emission. estimate binding mass 1 presumed nucleus on order 10^7 Msun. Alternatively, amplification radio circumnuclear molecular gas. In this case, high blueshift mean masing region moving outward away gas surrounding active nucleus.