East Asian VLBI Network Observations of Active Galactic Nuclei Jets:
  Imaging with KaVA+Tianma+Nanshan
  The East Asian very-long-baseline interferometry (VLBI) Network (EAVN) is a
rapidly evolving international VLBI array that is currently promoted under
joint efforts among China, Japan, and Korea. EAVN aims at forming a joint VLBI
Network by combining a large number of radio telescopes distributed over East
Asian regions. After the combination of the Korean VLBI Network (KVN) and the
VLBI Exploration of Radio Astrometry (VERA) into KaVA, further expansion with
the joint array in East Asia is actively promoted. Here we report the first
imaging results (at 22 and 43 GHz) of bright radio sources obtained with KaVA
connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China. To test
the EAVN imaging performance for different sources, we observed four active
galactic nuclei (AGN) having different brightness and morphology. As a result,
we confirmed that Tianma 65-m Radio Telescope (TMRT) significantly enhances the
overall array sensitivity, a factor of 4 improvement in baseline sensitivity
and 2 in image dynamic range compared to the case of KaVA only. The addition of
Nanshan 26-m Radio Telescope (NSRT) further doubled the east-west angular
resolution. With the resulting high-dynamic-range, high-resolution images with
EAVN (KaVA+TMRT+NSRT), various fine-scale structures in our targets, such as
the counter-jet in M87, a kink-like morphology of the 3C273 jet and the weak
emission in other sources, are successfully detected. This demonstrates the
powerful capability of EAVN to study AGN jets and to achieve other science
goals in general. Ongoing expansion of EAVN will further enhance the angular
resolution, detection sensitivity and frequency coverage of the network.
