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Keywords:

  • radiation mechanisms: non-thermal;
  • BL Lacertae objects: general;
  • radio continuum: galaxies;
  • gamma-rays: galaxies;
  • X-rays: galaxies

ABSTRACT

We study the quasi-simultaneous near-IR, optical, ultraviolet and X-ray photometry of 11 γ-ray selected blazars for which redshift estimates larger than 1.2 have been recently provided. Four of these objects turn out to be high-power blazars with the peak of their synchrotron emission between ∼3 × 1015 and ∼1016 Hz, and therefore of a kind predicted to exist but never seen before. This discovery has important implications for our understanding of physical processes in blazars, including the so-called ‘blazar sequence’, and might also help in constraining the extragalactic background light through γ-ray absorption since two sources are strongly detected even in the 10–100 GeV Fermi-LAT band. Based on our previous work and their high powers, these sources are very likely high-redshift flat-spectrum radio quasars, with their emission lines swamped by the non-thermal continuum.