Dynamical friction of radio galaxies in galaxy clusters

TL;DR

This paper investigates how dynamical friction causes luminous radio galaxies in galaxy clusters to migrate toward the center, resulting in a more concentrated distribution over a few billion years.

Contribution

It demonstrates that dynamical friction can explain the observed central concentration of radio galaxies in clusters within a realistic cosmological timeframe.

Findings

Radio galaxy distribution becomes more concentrated over 3-5 Gyr.

Dynamical friction accounts for the observed high concentration of radio galaxies.

Initial NFW profile evolves to a higher concentration profile due to dynamical friction.

Abstract

The distribution of luminous radio galaxies in galaxy clusters has been observed to be concentrated in the inner region. We consider the role of dynamical friction of massive galaxies ($M\sim 10^{12.5}$ M$_{\odot}$), assuming them to be hosts of luminous radio galaxies, and show that beginning with a Navarro-Frenk-White density profile of a cluster of mass $M_{cl}\sim 10^{15}$ M$_{\odot}$ of concentration $c\sim 5$ and collapsing at $z\sim 1$, the density profile of radio galaxies evolve to a profile of concentration $c \sim 25$, as observed, in a time scale of $t\sim 3\hbox{--}5$ Gyr.