Evidence for radio loud to radio quiet evolution from red and blue quasars

TL;DR

The paper provides evidence that quasars evolve from radio loud to radio quiet states, explaining their distribution patterns through different evolutionary timescales and black hole spin dynamics.

Contribution

It introduces a model linking quasar radio loudness evolution with black hole spin changes and distinct timescales for radio loud and quiet phases.

Findings

Red and blue QSOs approach each other at the radio quiet end.

Rapid evolution in radio loud phases results in fewer objects at high radio loudness.

Largest differences between red and blue QSOs occur at intermediate radio loudness.

Abstract

Recent work on red and blue quasi-stellar objects (QSOs) has identified peculiar number distributions as a function of radio loudness that we explore and attempt to explain from the perspective of a picture in which a subset of the population of active galaxies evolves from the radio loud to the radio quiet state. Because the time evolution is slowed down by an order of magnitude or more for the radio quiet phase, the numbers of red and blue QSOs approach each other at the extreme end of the radio quiet range of radio loudness with larger numbers. The rapid time evolution of most radio loud phases, instead, makes the numbers similar but lower at the far radio loud end. At the midpoint of radio loudness, instead, the differences between red and blue QSOs experience their largest values which results from accretion rapidly spinning black holes down but subsequently spinning them up more slowly. Recovering these basic features of the observations is evidence for rapid evolution away from radio loudness and slow evolution in radio quiet states.