Cold gas bubble inflated by a low-luminosity radio jet

¹ Joint Institute for VLBI ERIC, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
² ASTRON, The Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
³ Kapteyn Astronomical Institute, University of Groningen, PO Box 800 9700 AV Groningen, The Netherlands
⁴ Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Pune 411007, India
⁵ Astronomy and Space Sciences Department Faculty of Science, Erciyes University, 38039 Kayseri, Türkiye
⁶ Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France
⁷ Institut Universitaire de France, Ministère de l’Enseignement Supérieur et de la Recherche, 1 rue Descartes, 75231 Paris Cedex F-05, France
⁸ Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 3058577, Japan
⁹ Australian National University, Research School of Astronomy and Astrophysics, Cotter Rd., Weston, ACT 2611, Australia

^⋆ Corresponding author; murthy@jive.eu

Received: 23 November 2024
Accepted: 13 January 2025

Abstract

We present NOEMA CO(2–1) observations of a nearby, young, low-luminosity radio source, B2 0258+35. Our earlier CO(1–0) study had shown the presence of strong jet-ISM interaction and a massive molecular gas outflow involving 75% of the circumnuclear gas. Our follow-up CO(2–1) observations have revealed even more complex gas kinematics, where the southern radio jet is driving out molecular gas in the form of a swiftly expanding bubble, with velocities up to almost 400 km s⁻¹. We found highly elevated CO(2–1)/CO(1–0) line ratios for the gas belonging to the bubble and also further away from the radio jets. Previous observations have shown that the active galactic nucleus (AGN) in the host galaxy, NGC 1167, is in a very low-accretion state. Thus, we attribute the high line ratios to the high gas excitation caused by the jet–ISM interaction. The radio jets, despite exhibiting a relatively low luminosity (1.3 × 10⁴⁴ erg s⁻¹), are solely responsible for the observed extreme gas kinematics. This is one of the clearest detections of an expanding cold gas bubble in such a type of source, showing that the jets are affecting both the kinematics and physicals conditions of the gas. Our study adds to the growing store of evidence that low-luminosity radio sources can also affect the kinematics and physical conditions of the cold gas, which fuels star formation, in their host galaxies to a significant extent. Hence, such sources should be considered in models seeking to quantify feedback from radio AGN.