Tracing the energetic outflows from galactic nuclei: observational evidence for a large-scale bipolar radio and X-ray-emitting bubble-like structure in M106

Abstract

ABSTRACT The role of energetic outflows from galactic nuclei in shaping galaxy formation and evolution is still shrouded in uncertainty. In this study, we shed light on this complex phenomenon by presenting evidence for a large-scale bipolar radio/X-ray-emitting bubble-like structure emanating from the central region of the nearby disc galaxy M106 (NGC 4258). Our findings, based on Low-Frequency Array survey data and Chandra observations, provide a glimpse into the underlying physical processes driving this enigmatic structure. Similar to the eROSITA/Fermi bubbles in our own Galaxy, the M106 bubbles enclose diffuse hot plasma and are partially bounded by prominent radio/X-ray-emitting edges. We constrain the magnetic field and cosmic-ray properties of the structure. The analysis of the X-ray data gives an estimate of the thermal energy of the bubbles as ∼8 × 1056 erg. This energy can be supplied by the jets and perhaps by the wind from the accretion flow of the galaxy’s low-luminosity AGN, which most likely has been much more powerful in the recent past, with an average mechanical energy release rate of ∼4 × 1042 erg s−1 over the last ∼8 × 106 yr – the estimated age of the structure. We also show evidence for diffuse X-ray emission on larger scales, indicating the presence of a hot galactic corona. Our results provide a clear manifestation of galactic nuclear feedback regulating the gas content and energetics of the circumgalactic medium of disc galaxies similar to our own.