A small radio galaxy at z=4.026
  Less than $200$ radio-loud active galactic nuclei (AGN) 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 with
jets pointing at small angles to the observer's line of sight. But there are
also objects with no sign of relativistic beaming possibly having larger jet
inclination angles. In a couple of cases, X-ray observations indicate the
presence of relativistic beaming in contrary to the VLBI measurements made with
the European VLBI Network (EVN). J1420$+$1205 is a prominent example, where our
$30-100$ mas-scale enhanced Multi Element Remotely Linked Interferometer
Network (e-MERLIN) radio observations revealed a rich structure reminiscent of
a small radio galaxy. It shows a bright hotspot which might be related to the
denser interstellar medium around a young galaxy at an early cosmological
epoch.
