Feedback factory: multiple faint radio jets detected in a cluster at z = 2

Abstract

ABSTRACT We report the detection of multiple faint radio sources, that we identify as active galactic nucleus (AGN) jets, within CLJ1449+0856 at z = 2 using 3 GHz Very Large Array observations. We study the effects of radio-jet-based kinetic feedback at high redshifts, which has been found to be crucial in low-redshift clusters to explain the observed thermodynamic properties of their intracluster medium (ICM). We investigate this interaction at an epoch featuring high levels of AGN activity and a transitional phase of ICM in regards to the likelihood of residual cold gas accretion. We measure a total flux of $\rm 30.6 \pm 3.3\, \mu Jy$ from the six detected jets. Their power contribution is estimated to be $1.2 \, (\pm 0.6)\, \times 10^{44} \, \rm erg\, s^{-1}$, although this value could be up to $4.7 \, \times 10^{44} \, \rm erg\, s^{-1}$. This is a factor of ∼0.25–1.0 of the previously estimated instantaneous energy injection into the ICM of CLJ1449+0856 from AGN outflows and star formation that have already been found to be sufficient in globally offsetting the cooling flows in the cluster core. In line with the already detected abundance of star formation, this mode of feedback being distributed over multiple sites, contrary to a single central source observed at low redshifts, points to accretion of gas into the cluster centre. This also suggests a ‘steady state’ of the cluster featuring non-cool-core-like behaviour. Finally, we also examine the total infrared–radio luminosity ratio for the known sample of galaxies within the cluster core and find that dense environments do not have any serious consequence on the compliance of galaxies to the infrared–radio correlation.