Paper

LeMMINGs. III. The e-MERLIN Legacy Survey of the Palomar sample. Exploring the origin of nuclear radio emission in active and inactive galaxies through the O III -- radio connection

Zanisi, L, Pahari, M, Alberdi, A, Bendo, G J, Knapen, J H, Argo, M K, Körding, E, Saikia, D J, Panessa, F, Saikia, P, Corbel, S, Aalto, S, Brinks, E, Martí-Vidal, I, Mundell, C G, Beswick, R J, Mutie, I, Maccarone, T J, Green, D A, Williams, D R A, Pérez-Torres, M A, Baan, W A, McHardy, I, Ward, M J, Fenech, D M, Baldi, R D, Shankar, F, Dullo, B T, Spencer, R E, Marcaide, J M, Stevens, I R, Uttley, P, H -R Klöckner, Romero-Cañizales, C

2021

Overview

What determines the nuclear radio emission in local galaxies? We combine optical [O III] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically-complete sample of 280 nearby, optically active (LINER and Seyfert) and inactive HII and Absorption line galaxies [ALG]) galaxies. Using [O III] luminosity (\\(L_{\\rm [O~III]}\\)) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical-radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores (\\(L_{\\rm core}\\)) is found to scale with BH mass (\\(M_{\\rm BH}\\)) and [O~III] luminosity. Below \\(M_{\\rm BH} \\sim\\)10\\(^{6.5}\\) M\\(_{\\odot}\\), stellar processes from non-jetted HII galaxies dominate with \\(L_{\\rm core} \\propto M_{\\rm BH}^{0.61\\pm0.33}\\) and \\(L_{\\rm core} \\propto L_{\\rm [O~III]}^{0.79\\pm0.30}\\). Above \\(M_{\\rm BH} \\sim\\)10\\(^{6.5}\\) M\\(_{\\odot}\\), accretion-driven processes dominate with \\(L_{\\rm core} \\propto M_{\\rm BH}^{1.5-1.65}\\) and \\(L_{\\rm core} \\propto L_{\\rm [O~III]}^{0.99-1.31}\\) for active galaxies: radio-quiet/loud LINERs, Seyferts and jetted HII galaxies always display (although low) signatures of radio-emitting BH activity, with \\(L_{\\rm 1.5\\, GHz}\\gtrsim\\)10\\(^{19.8}\\) W Hz\\(^{-1}\\) and \\(M_{\\rm BH}\\gtrsim10^{7}\\) M\\(_{\\odot}\\), on a broad range of Eddington-scaled accretion rates (\\(\\dot{m}\\)). Radio-quiet and radio-loud LINERs are powered by low-\\(\\dot{m}\\) discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-\\(\\dot{m}\\) discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted HII galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. [abridged]

• Publisher: Cornell University Library, arXiv.org
• Subject: Accretion disks / Active galaxies / Deposition / Jets / Linings / Luminosity / Nuclear fuels / Optical activity / Radio astronomy / Radio emission / Relativistic effects / Seyfert galaxies