Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Experiment Videos

Difficulties with unification.

A K Singal1

  • 1Netherlands Founation for Research in Astronomy, Dwingeloo, The Netherlands.

Proceedings of the National Academy of Sciences of the United States of America
|December 5, 1995
PubMed
Summary
This summary is machine-generated.

Related Concept Videos

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

Correction to: The MELD Score Is Superior to the Maddrey Discriminant Function Score to Predict Short-Term Mortality in Alcohol-Associated Hepatitis: A Global Study.

The American journal of gastroenterology·2022
Same author

The MELD Score Is Superior to the Maddrey Discriminant Function Score to Predict Short-Term Mortality in Alcohol-Associated Hepatitis: A Global Study.

The American journal of gastroenterology·2021
Same author

Relapse of porphyria cutanea tarda after treatment with phlebotomy or 4-aminoquinoline antimalarials: a meta-analysis.

The British journal of dermatology·2018
Same author

Management of hepatocellular carcinoma.

Journal of cancer research and clinical oncology·2014
Same author

Editorial: sepsis in cirrhosis - there may be trouble ahead; authors' reply.

Alimentary pharmacology & therapeutics·2014
Same author

Prevalence and in-hospital mortality trends of infections among patients with cirrhosis: a nationwide study of hospitalised patients in the United States.

Alimentary pharmacology & therapeutics·2014
Same journal

Chemotactic self-organization captures the dynamics of mammalian hair follicle patterning.

Proceedings of the National Academy of Sciences of the United States of America·2026
Same journal

Tomographic imaging of superconducting order using particle-hole interference.

Proceedings of the National Academy of Sciences of the United States of America·2026
Same journal

Inhibitory potential of autologous neutralizing antibodies sets quantitative limits on the rebound-competent HIV-1 reservoir.

Proceedings of the National Academy of Sciences of the United States of America·2026
Same journal

Inferring epidemiological parameters under an infectious phylogeography model with visitor dynamics.

Proceedings of the National Academy of Sciences of the United States of America·2026
Same journal

Analytical modeling for suction cup designs for skin-interfaced wearable devices.

Proceedings of the National Academy of Sciences of the United States of America·2026
Same journal

Improving cell-free metabolism through direct integration of artificial respiratory chains.

Proceedings of the National Academy of Sciences of the United States of America·2026
See all related articles

Orientation-based unified schemes struggle to explain quasar and radio galaxy observations. Number ratios in orientation-bias-free samples vary with redshift and luminosity, contradicting simple models.

Area of Science:

  • Extragalactic Astronomy
  • Active Galactic Nuclei (AGN) Research

Background:

  • Unified schemes propose that quasars and radio galaxies are intrinsically similar, differing only in their viewing angle.
  • These models often assume a fixed torus opening angle (around 45 degrees) obscuring the active galactic nucleus.
  • Previous studies relied on samples potentially affected by orientation bias, limiting definitive conclusions.

Purpose of the Study:

  • To critically evaluate orientation-based unified scheme models using meter-wavelength selected samples, which are less prone to orientation bias.
  • To investigate discrepancies between model predictions and observational data regarding quasar and radio galaxy populations.
  • To explore the implications of these discrepancies for modified unified scheme models.

Main Methods:

Related Experiment Videos

  • Analysis of meter-wavelength selected samples of quasars and radio galaxies, assumed to be largely free of orientation bias.
  • Comparison of observed quasar-to-radio galaxy number ratios with predictions from simple orientation-based unified schemes.
  • Examination of the dependence of these ratios on redshift, flux density, and radio luminosity.
  • Assessment of the impact of varying torus opening angles and cosmological evolution on model predictions.

    • Main Results:

    • Observed quasar-to-radio galaxy number ratios in orientation-bias-free samples do not align with expectations of simple unified schemes.
    • The observed ratios exhibit a strong dependence on redshift, flux density, and radio luminosity.
    • Even with cosmological evolution of the torus opening angle, significant differences in luminosity-redshift plane size distributions between radio galaxies and quasars remain unexplained.

    Conclusions:

    • Simple orientation-based unified schemes, with a fixed average torus opening angle, are insufficient to explain current observational data.
    • The observed dependencies suggest that factors beyond simple orientation, or a more complex evolutionary scenario, are at play.
    • These findings necessitate revisions to or alternatives to current unified scheme models for active galactic nuclei.