The Relationship Between Beam Power and Radio Power for Classical Double Radio Sources

TL;DR

This study establishes a quantitative relationship between beam power and radio power in classical double radio sources, enabling radio power to serve as a proxy for beam power, with no significant redshift evolution observed.

Contribution

The paper derives an empirical formula linking beam power and radio power for classical double radio sources, facilitating easier estimation of beam power from radio observations.

Findings

Beam power relates to radio power via Log(Lj) = 0.84 Log(P) + 2.15.

Conversion efficiency from beam to radio power is about 0.7%.

No significant redshift evolution of the beam-to-radio power ratio was found.

Abstract

Beam power is a fundamental parameter that describes, in part, the state of a supermassive black hole system. Determining the beam powers of powerful classical double radio sources requires substantial observing time, so it would be useful to determine the relationship between beam power and radio power so that radio power could be used as a proxy for beam power. A sample of 31 powerful classical double radio sources with previously determined beam and radio powers are studied; the sources have redshifts between about 0.056 and 1.8. It is found that the relationship between beam power, Lj, and radio power, P, is well described by Log(Lj) = 0.84 Log(P) + 2.15, where both L_j and P are in units of 10^(44) erg/s. This indicates that beam power is converted to radio power with an efficiency of about 0.7%. The ratio of beam power to radio power is studied as a function of redshift; there is no significant evidence for redshift evolution of this ratio over the redshift range studied. The relationship is consistent with empirical results obtained by Cavagnolo et al. (2010) for radio sources in gas rich environments, which are primarily FRI sources, and with the theoretical predictions of Willott et al. (1999).