Nustar view of the central region of the Perseus cluster

TL;DR

This study presents NuSTAR observations of the central AGN in the Perseus cluster, revealing a dominant hard X-ray power-law component likely originating from the jet, with spectral analysis ruling out thermal accretion disk emission.

Contribution

First NuSTAR spectral analysis of 3C 84 that decomposes the AGN's hard X-ray emission and suggests a jet origin over thermal accretion disk processes.

Findings

Power-law component dominates above 20 keV with photon index ~1.9

Hard X-ray flux correlates with hardness ratio variations

Thermal emission from the accretion disk is insufficient to explain observed X-rays

Abstract

Located at the center of the Perseus cluster, 3C 84 is an extremely bright and nearby radio galaxy. Because of the strong diffuse thermal emission from the cluster in X-rays, the detailed properties and the origin of a power-law component from the central active galactic nucleus (AGN) remains unclear in the source. We report here the first NuSTAR observations of 3C 84. The source was observed for 24.2 and 32 ks on February 01 and 04, 2018, respectively. NuSTAR observations spectrally decompose the power-law AGN component above 10 keV. The power-law component dominates the spectrum above 20 keV with a photon index $\sim$1.9 and an energy flux F$_{20-30 keV}$ = 1.0 $\times$10$^{-11}$ erg cm$^{-2}$ s$^{-1}$, corresponding to an isotropic luminosity, $L_{20-30 keV}$ = 7.4$\times$10$^{42}$ erg s$^{-1}$. We discuss possible emitting sites for the power-law component. The expected thermal emission from the accretion disk is not hot enough to account for the hard X-rays detected from the source. Similar X-ray and $\gamma$-ray photon indices and long-term flux variations, the absence of cutoff energy in the hard X-ray spectrum of the source, correlated hard X-ray flux and hardness ratio variations, and the similarity of optical-X-ray slope to blazar rather than Seyfert galaxies supports the hard X-ray power-law component originating from the jet.