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Superluminal sources.

R C Vermeulen1

  • 1Owens Valley Radio Observatory, California Institute of Technology, Pasadena, CA 91125, USA.

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

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This study analyzes apparent velocity statistics in radio jet sources, finding no evidence for distinct populations. The distribution suggests a skewed Lorentz factor distribution, impacting cosmological models.

Area of Science:

  • Astrophysics
  • Cosmology
  • Radio Astronomy

Background:

  • Apparent velocity statistics of extragalactic radio sources are crucial for understanding jet physics and cosmology.
  • Beaming models predict specific velocity distributions, which need observational validation.

Purpose of the Study:

  • To present predictions for apparent velocity statistics under simple beaming models.
  • To compare these predictions with observational data from a large, homogeneous survey.
  • To discuss applications for testing unification models and for cosmological measurements (Hubble constant, deceleration parameter).

Main Methods:

  • Comparison of theoretical predictions from simple beaming models with observed apparent velocity statistics.
  • Analysis of data from a large, homogeneous survey of radio sources.

Related Experiment Videos

  • Examination of the relationship between apparent velocity and observed luminosity.

    • Main Results:

    • The data do not provide compelling evidence for intrinsically different populations of galaxies, BL Lacertae objects, or quasars.
    • Apparent velocities (βapp) in the range 1-5 h⁻¹ (where h = H₀/100 km s⁻¹ Mpc⁻¹) occur with roughly equal frequency.
    • Higher βapp values (up to 10 h⁻¹) are scarcer than previously reported, suggesting earlier studies focused on non-representative sources.
    • The βapp distribution indicates a skewed distribution of Lorentz factors (γb), peaking around 2 h⁻¹ and extending to at least 10 h⁻¹.
    • A rising upper envelope in the βapp distribution is observed as a function of 5-GHz luminosity.

    Conclusions:

    • The observed apparent velocity statistics are consistent with simple beaming models and suggest a skewed distribution of Lorentz factors.
    • The findings challenge the notion of intrinsically different source populations and highlight the importance of representative samples.
    • Combined analysis of source counts and apparent velocity statistics in larger samples can offer significant insights into radio jet source properties and cosmological parameters.