AGN-Induced Cavities in NGC 1399 and NGC 4649

TL;DR

This study analyzes X-ray and radio observations of NGC 1399 and NGC 4649 to measure AGN-induced cavities, jet power, and particle content, revealing differences in electron populations and entrainment between the galaxies.

Contribution

It provides the first detailed calculation of jet power and particle energy ratios in cavities of NGC 1399 and NGC 4649, highlighting differences in electron populations.

Findings

Jet power estimates are ~8-14 x 10^{41} erg/s for NGC 1399.

k/f values indicate few entrained particles in NGC 1399, but many in NGC 4649.

Electron spectrum models fit NGC 1399 well, less so for NGC 4649.

Abstract

We present an analysis of archival Chandra and VLA observations of the E0 galaxy NGC 1399 and the E2 galaxy NGC 4649 in which we investigate cavities in the surrounding X-ray emitting medium caused by the central AGN. We calculate the jet power required for the AGN to evacuate these cavities and find values of ~8x10^{41} erg/s and ~14x10^{41} erg/s for the lobes of NGC 1399 and ~7x10^{41} erg/s and ~6x10^{41} erg/s for those of NGC 4649. We also calculate the k/f values for each cavity, where k is the ratio of the total particle energy to that of electrons radiating in the range of 10 MHz to 10 GHz, and f is the volume filling factor of the plasma in the cavity. We find that the values of k/f for the lobes of NGC 1399 are ~93 and ~190, and those of the lobes of NGC 4649 are ~15000 and ~12000. We conclude that the assumed spectrum describes the electron distribution in the lobes of NGC 1399 reasonably well, and that there are few entrained particles. For NGC 4649, either there are many entrained particles or the model spectrum does not accurately describe the population of electrons.