Mean and Extreme Radio Properties of Quasars and the Origin of Radio Emission

Abstract

I investigate the evolution of both the radio-loud fraction (RLF) and, using a stacking analysis, the mean radio-loudness of quasars. I consider how these values evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission line region. I match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric) primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high-redshift, I find that both the RLF and the mean radio-loudness increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio-loudness increase for quasars that are argued to have weaker radiation line-driven wind components of the broad emission line region. In agreement with past work, I find that the RLF increases with increasing optical luminosity and decreasing redshift while the mean radio-loudness evolves in the exact opposite manner. This difference in behavior in the L-z plane may indicate selection effects that bias an understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, I argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences. Only RQ quasars at one extreme of the distribution are likely to become RL through slight differences in spin and/or merger history.%%%%Ph.D., Physics – Drexel University, 2014