Detection of a radio-filled X-ray cavity within the interstellar medium of NGC 5141

Abstract

We present the first Chandra detection of a single X-ray cavity within the interstellar medium of the small Fanaroff-Riley type I radio galaxy NGC 5141. The X-ray surface brightness depression, located ≈4 kpc away from the galaxy center, is projected on the northern radio lobe, which is completely contained within the galaxy. The thermal gas surrounding the cavity, which extends to ≃20 kpc, has a bolometric X-ray luminosity (0.1–100 keV) of LX ≈ 2 × 1040 erg s−1 and a temperature of kT ≈ 0.8 keV. We calculated the total energy (Ecav = 4PV ≈ 1055 erg) required to inflate the cavity and its age (tcav ≈ 9 Myrs), assuming that it is filled with relativistic particles and rises buoyantly. The inferred total cavity power is as low as Pcav = Ecav/tcav ≈ 6 × 1040 erg s−1, which is the lowest one among the radio-filled systems. Comparing Pcav to the bolometric X-ray luminosity (i.e., the cooling luminosity), we conclude that NGC 5141’s central active galactic nucleus can heat the interstellar medium and balance its cooling luminosity, confirming that the Pcav − Lcool relation, mainly tested on groups and clusters, also works for such a low-power system.