The host galaxies of radio AGN: New views from combining LoTSS and MaNGA observations

¹ Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany
² Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
³ Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB, UK
⁴ National Centre for Nuclear Research, Pasteura 7, PL-02093 Warsaw, Poland

^⋆ Corresponding author; gxjin@mpa-garching.mpg.de

Received: 23 August 2024
Accepted: 15 January 2025

Abstract

The role of radio mode active galactic nuclei (AGN) feedback on galaxy evolution is still under debate. In this study we utilized a combination of radio continuum observations and optical integral field spectroscopic (IFS) data to explore the impact of radio AGN on the evolution of their host galaxies at global and subgalactic scales. We constructed a comprehensive radio-IFS sample comprising 5548 galaxies with redshift z < 0.15 by cross-matching the LOFAR Two-Metre Sky Survey (LoTSS) with the Mapping Nearby Galaxies at APO (MaNGA) survey. We revisited the tight linear radio continuum–star formation relation and quantify its intrinsic scatter, then used the relation to classify 616 radio-excess AGN with excessive radio luminosities over the values expected from their star formation rates. Massive radio AGN host galaxies are predominantly quiescent systems, but the quenching level shows no correlation with the jet luminosity. The mass assembly histories derived from the stellar population synthesis model fitting agree with the cosmological simulations incorporating radio-mode AGN feedback models. We observe that radio AGN hosts grow faster than a control sample of galaxies matched in stellar mass, and the quenching age (∼5 Gyr) is at larger lookback times than the typical radio jet age (< 1 Gyr). By stacking the spectra in different radial bins and comparing results for radio AGN hosts and their controls, we find emission line excess features in the nuclear region of radio AGN hosts. This excess is more prominent in low-luminosity, low-mass, and compact radio AGN. The [N II]/Hα ratios of the excessive emission line indicate that radio AGN or related jets are ionizing the surrounding interstellar medium in the vicinity of the nucleus. Our results support the scenario that the observed present-day radio AGN activity may help their host galaxies maintain quiescence through gas ionization and heating, but it is not responsible for the past quenching of their hosts.