Evolutionary Tracks of Individual Quasars in the Mass-Luminosity Plane

TL;DR

This paper models the evolution of individual quasars in the mass-luminosity plane, constraining their growth tracks and lifetimes to match observed distributions across redshifts, suggesting rapid decline in accretion rates.

Contribution

It introduces simple evolutionary models for quasars that fit observed data and constrain quasar lifetimes, duty cycles, and decline rates in Eddington ratios.

Findings

Quasar evolution tracks are constrained within observed distributions.

Models suggest short quasar lifetimes of 1-2 Gyr.

Rapid decline in Eddington ratio, possibly as t^-6 or steeper.

Abstract

Previous work on the quasar mass-luminosity plane indicates the possibility that quasars of the same central black hole mass might follow a common evolutionary track, independent of the properties of the host galaxy. We consider two simple models for the evolution of individual quasars. Requiring these tracks to lie within the observed quasar locus at all redshifts strongly constrains the model parameters, but does allow some solutions. These solutions include a family of tracks with similar shape but different initial masses that might match the observed quasar distributions at all redshifts z < 2.0. This family of solutions is characterized by short (1-2 Gyr) lifetimes, a duty cycle in which the quasar is on at least 25% of the time, and a rapid decline in Eddington ratio, perhaps with L/L_Edd ~ t^-6 or steeper.