SDSS J114657.79+403708.6: The third most distant blazar at z = 5.0

The radio-loud quasar SDSS J114657.79+403708.6 at a redshift z = 5.0 is one of the most distant radio-loud objects. The IR-optical luminosity and spectrum suggest that its black hole has a very large mass:M= (5 ± 1) × 109M⊙. The radio-loudness (ratio of the radio to optical flux) of the source is large (around 100), suggesting that the source is viewed at small angles from the jet axis, and could be a blazar. The X-ray observations fully confirm this hypothesis, due to the high level and hardness of the flux. This makes SDSS J114657.79+403708.6 the third most distant blazar known, after Q0906+693 (z = 5.47) and B2 1023+25 (z = 5.3). Among those, SDSS J114657.79+403708.6 has the largest black holemass, setting interesting constraints on the mass function of heavy (>109M⊙) black holes at high redshifts. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.