MERLIN and EVN observations of a z=4.515 radio galaxy, RC J0311+0507, and the problem of SMBHs in the early Universe

Abstract

RC J0311+0507, the parent galaxy of which has a redshift, z, of 4.514, is one of the most luminous objects in the High-z radio Universe. New MERLIN and EVN intensity and polarization maps of the object at 1.7 GHz and 5 GHz show multiple compact components and extended emission orientated in a primarily NS direction on either side of what appears to be a core. The flux density ratio between the southern and northern components is highly asymmetric, with values of ∼30 at 5 GHz and ∼10 at 1.7 GHz. New optical observations using the Russian 6-m optical telescope confirm the identification of the radio source with a galaxy, and show the presence of extended Ly α emission. The very high radio luminosities and the high "bulge optical emission" suggest the presence of a very massive (10 9 M ⊙ ) Black Hole (BH). Assuming that the age of the Universe at z = 4.514 is only ∼1.3 Gyr and that the standard epoch for the formation of galaxies is within the redshift range from 7 to 10, there is less than 0.5 Gyr available for the formation of RC J0311+0507. The quick growth of a BH mass solely as a result of a merger is questionable, and the simple evolution from several solar masses to 10 9 M ⊙ in a timescale of less 1 Gyr appears to be very improbable.10th European VLBI Network Symposium and EVN Users Meeting: VLBI and the new generation of radio arrays