Active galactic nuclei-induced cavities in NGC 1399 and NGC 4649

We present an analysis of archival Chandra and Very Large Array 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 active galactic nuclei (AGN). We calculate the jet power required for the AGN to evacuate these cavities and find values of ∼8 × 1041 and ∼14 × 1041erg s−1 for the lobes of NGC 1399 and ∼7 × 1041 and ∼6 × 1041erg s−1 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 ∼15 000 and ∼12 000. 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.