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

Research output: Contribution to journalArticlepeer-review

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


What determines the nuclear radio emission in local galaxies? To address this question, 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 [H ii and absorption line galaxies (ALGs)] galaxies. Using [O iii] luminosity (L[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 (Lcore) is found to scale with BH mass (MBH) and [O iii] luminosity. Below MBH ∼106.5 M⊙, stellar processes from non-jetted H ii galaxies dominate with Lcore ∝ MBH0.61 ± 0.33 and Lcore ∝ L[O III]0.79 ± 0.30. Above MBH ∼106.5 M⊙, accretion-driven processes dominate with Lcore ∝ MBH1.5-1.65 and Lcore ∝ L[O III]0.99-1.31 for active galaxies: radio-quiet/loud LINERs, Seyferts, and jetted H ii galaxies always display (although low) signatures of radio-emitting BH activity, with L1.5 GHz ≳ 1019.8 W Hz-1 and MBH ≳ 107 M⊙, on a broad range of Eddington-scaled accretion rates (m). Radio-quiet and radio-loud LINERs are powered by low-m discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-m discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted H ii galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. In conclusion, specific accretion-ejection states of active BHs determine the radio production and the optical classification of local active galaxies.

Bibliographical metadata

Original languageEnglish
Pages (from-to)2019-2038
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date15 Oct 2021
Publication statusPublished - 1 Dec 2021