The hyperluminous, dust-obscured quasar W2246-0526 at z=4.6: detection
  of parsec-scale radio activity
  WISE J224607.56$-$052634.9 (W2246-0526) is a hyperluminous ($L_{\rm
bol}\approx 1.7\times 10^{14}~L_\odot$), dust-obscured and radio-quiet quasar
at redshift $z=4.6$. It plays a key role in probing the transition stage
between dusty starbursts and unobscured quasars in the co-evolution of galaxies
and supermassive black holes (SMBHs). To search for the evidence of the jet
activity launched by the SMBH in W2246-0526, we performed very long baseline
interferometry (VLBI) observations of its radio counterpart with the European
VLBI Network (EVN) plus the enhanced Multi Element Remotely Linked
Interferometer Network (e-MERLIN) at 1.66 GHz and the Very Long Baseline Array
(VLBA) at 1.44 and 1.66 GHz. The deep EVN plus e-MERLIN observations detect a
compact (size $\leq32$ pc) sub-mJy component contributing about ten percent of
its total flux density, which spatially coincides with the peak of dust
continuum and [C II] emissions. Together with its relatively high brightness
temperature ($\geq8\times10^{6}$ K), we interpret the component as a
consequence of non-thermal radio activity powered by the central SMBH, which
likely originates from a stationary jet base. The resolved-out radio emission
possibly come from a diffuse jet, quasar-driven winds, or both, while the
contribution by star formation activity is negligible. Moreover, we propose an
updated geometry structure of its multi-wavelength active nucleus and shed
light on the radio quasar selection bias towards the blazars at $z>4$.
