The Jet Power and Emission Line Correlations of Radio Loud Optically Selected Quasars

TL;DR

This study examines the extended radio emission and jet power in SDSS quasars at low redshift, revealing weak correlations with accretion luminosity and highlighting the rarity of extremely powerful jets.

Contribution

It provides the first detailed analysis of extended radio emission in optically selected quasars and clarifies the relationship between jet power and accretion luminosity.

Findings

2.7% of quasars have extended radio emission >20 kpc.

Jet powers peak around 3×10^{44} erg/sec, with very few exceeding 10^{45} erg/sec.

Weak correlation between jet power and bolometric luminosity.

Abstract

In this Letter, the properties of the extended radio emission form SDSS DR7 quasars with $0.4<z<0.8$ is studied. This low redshift sample is useful since any corresponding FIRST radio observations are sensitive enough to detect extended flux in even the weakest FR II radio sources. In the sample, 2.7% of the sources have detectable extended emission on larger than galactic scales ($>$ 20 - 30 kpc). The frequency of quasars with FR II level extended radio emission is $\approx 2.3%$ and $>0.4%$ of quasars have FR I level extended radio emission. The lower limit simply reflects the flux density limit of the survey. The distribution of the long term time averaged jet powers of these quasars, $\bar{Q}$, has a broad peak $\sim 3\times 10^{44}$ ergs/sec that turns over below below $10^{44}$ ergs/sec and sources above $10^{45}$ ergs/sec are extremely rare. It is found that the correlation between the bolometric (total thermal) luminosity of the accretion flow, $L_{bol}$, and $\bar{Q}$ is not strong. The correlation of $\bar{Q}$ with narrow line luminosity is stronger than the correlation with broad line luminosity and the continuum luminosity. It is therefore concluded that previous interpretations of correlations of $\bar{Q}$ with narrow line strengths in radio galaxies as a direct correlation of jet power and accretion power have been overstated. It is explained why this interpretation mistakenly overlooks the sizeable fraction of sources with weak accretion luminosity and powerful jets discovered by Ogle et al (2006).