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.

Deep Chandra Observations of A2495: A Possible Sloshing-regulated Feedback Cycle in a Triple-offset Galaxy Cluster

“…Then, the counts in the region of the putative depression are compared with the average azimuthal value at the same distance from the X-ray peak. This is the method used by Hlavacek-Larrondo et al (2015); Macconi et al (2022), but the irregular morphology of the ICM made this analysis not trivial. We obtained the following results: O1 2.8σ, O2 5.6σ, I1 0.6σ, I2 2.2σ.…”

“…The peculiar and asymmetric morphology of the ICM makes a reliable estimation of the surface brightness deficit and its significance not trivial, even with the high number of counts provided by the new Chandra observations. We adopted three methods, the first based on the azimuthal comparison shown in Hlavacek-Larrondo et al (2015), Macconi et al (2022), the second exploiting only the local value of the ICM around the putative cavity (as done in Ubertosi et al 2021b), and the last performing a radial comparison. In all cases, the number of counts from a region containing the depression and from a region without them were used to calculate the significance with the following definition:…”