Missing Baryons, from Clusters to Groups of Galaxies

TL;DR

This paper explains the observed scarcity of baryons in galaxy clusters and groups by analyzing how energy inputs from active galactic nuclei affect the intracluster plasma, matching observed X-ray luminosity-temperature relations.

Contribution

It introduces a model linking AGN energy feedback to the missing baryons problem, aligning theoretical predictions with observational data.

Findings

L_X-T relation shape and evolution match observations

AGN feedback explains baryon scarcity in clusters

Predicts future observational patterns

Abstract

From clusters to groups of galaxies, the powerful bremsstrahlung radiation L_X emitted in X rays by the intracluster plasma is observed to decline sharply with lowering virial temperatures T (i.e., at shallower depths of the gravitational wells) after a steep local L_X-T correlation; this implies increasing scarcity of diffuse baryons relative to dark matter, well under the cosmic fraction. We show how the widely debated issue concerning these `missing baryons' is solved in terms of the thermal and/or dynamical effects of the kinetic (at low redshifts z) and radiative (at high z) energy inputs from central active galactic nuclei, of which independent evidence is being observed. From these inputs we compute shape and z-evolution expected for L_X-T correlation which agree with the existing data, and provide a predictive pattern for future observations.