YZ

Yingkang Zhang

7 records found

There is still a limited number of high-redshift (z > 3) active galactic nuclei (AGNs) whose jet kinematics have been studied with very long baseline interferometry (VLBI). Without a dedicated proper motion survey, regularly conducted astrometric VLBI observations of bright ra ...
There are approximately 250 quasars discovered at redshift z ≥ 6, of which only a handful were detected in radio bands, and even fewer were imaged with the highest resolution very long baseline interferometry (VLBI) technique. Here we report the results of our dual-frequency obse ...

J2102+6015

A potential distant multimessenger?

We present and briefly discuss results of several studies of the source J2102+6015 with tentatively defined redshift z = 4.575 which demonstrates unusual properties in imaging and astrometric VLBI observations. Its properties might be considered as indications on the supermassive ...

Radio-loud Quasars above Redshift 4

Very Long Baseline Interferometry (VLBI) Imaging of an Extended Sample

High-redshift radio sources provide plentiful opportunities for studying the formation and evolution of early galaxies and supermassive black holes. However, the number of known radio-loud active galactic nuclei (AGN) above redshift 4 is rather limited. At high redshifts, it appe ...
Less than 200 radio-loud active galactic nuclei are known above redshift 4. Around 40 of them have been observed at milliarcsecond (mas) scale resolution with very long baseline interferometry (VLBI) technique. Some of them are unresolved, compact, relativistically beamed objects ...
Blazars are a sub-class of quasars with Doppler boosted jets oriented close to the line of sight, and thus efficient probes of supermassive black hole growth and their environment, especially at high redshifts. Here we report on Very Long Baseline Interferometry observations of a ...

J0906+6930

A radio quasar in the early Universe

Radio-loud high-redshift quasars (HRQs), although only a few of them are known to date, are crucial for studies of the growth of supermassive black holes (SMBHs) and the evolution of active galactic nuclei at early cosmological epochs. Radio jets offer direct evidence of SMBHs, a ...