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

¹ Dipartimento di Fisica e Astronomia, Alma Mater Studiorum, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
e-mail: duccio.macconi2@unibo.it
² INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna (OAS), Area della Ricerca CNR, Via Gobetti 101, 40129 Bologna, Italy
³ INAF, Istituto di Radioastronomia di Bologna (IRA), Via Gobetti 101, 40129 Bologna, Italy
⁴ University of California Observatories/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA

Received: 31 December 2021
Accepted: 28 January 2022

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 L_X ≈ 2 × 10⁴⁰ erg s⁻¹ and a temperature of kT ≈ 0.8 keV. We calculated the total energy (E_cav = 4PV ≈ 10⁵⁵ erg) required to inflate the cavity and its age (t_cav ≈ 9 Myrs), assuming that it is filled with relativistic particles and rises buoyantly. The inferred total cavity power is as low as P_cav = E_cav/t_cav ≈ 6 × 10⁴⁰ erg s⁻¹, which is the lowest one among the radio-filled systems. Comparing P_cav 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 P_cav − L_cool relation, mainly tested on groups and clusters, also works for such a low-power system.