On the unified scheme for high-excitation galaxies and quasars in 3CRR sample

  • F. C. OdoEmail author
  • P. E. Okobi
  • J. A. Alhassan
  • A. A. Ubachukwu


In this paper, we use the distributions of luminosity (P) and radio size (D) to re-examine the consistency of the unified scheme of high-excitation radio galaxies and quasars in the recently updated 3CRR sample. Based on a standard cosmology, we derive theoretically and show from observed data, the luminosity limit above which the 3CRR objects are well-sampled. We find, on average, a quasar fraction \(\sim \) 0.44 and galaxy-to-quasar size ratio \(\approx \) 2. Assuming a relativistic outflow of jet materials, we find a mean angle to the line of sight in the range \(35^{\circ }\,\le \,\phi \,\le 44^{\circ }\) for the quasars. On supposition of luminosity and orientation-dependent linear size evolution, expressed in a general functional form \(D_{(P,z,\phi )}\,\approx \,P^{\pm q}\)(1+\(z)^{-w}\)sin\(\phi \), we show that above the flux detection threshold of the 3CRR sample, high-excitation galaxies and quasars undergo similar evolution with \(q = -\,0.5\); \(w = -\,0.27\) and luminosity independent evolution parameter \(x = 2.27\), when orientation effect is accounted for. The results are consistent with orientation-based unified scheme for radio galaxies and quasars.


Galaxies: active galaxies: quasars general 



The authors are grateful to the anonymous referee for invaluable suggestions.


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Copyright information

© Indian Academy of Sciences 2019

Authors and Affiliations

  • F. C. Odo
    • 1
    Email author
  • P. E. Okobi
    • 1
  • J. A. Alhassan
    • 1
  • A. A. Ubachukwu
    • 1
  1. 1.Department of Physics and AstronomyUniversity of NigeriaNsukkaNigeria

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