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
  • Megan Argo
  • S. Aalto
  • A. Alberdi
  • W. A. Baan
  • Danielle Fenech
  • D. A. Green
  • H.-R. Klöckner
  • E. Körding
  • T. J. Maccarone
  • J. M. Marcaide
  • Isaac Mutie
  • F. Panessa
  • M. A. Pérez-Torres
  • C. Romero-Cañizales
  • D. J. Saikia
  • P. Saikia
  • F. Shankar
  • Ralph 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? 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[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∼10**6.5 M⊙, stellar processes from non-jetted HII galaxies dominate with Lcore∝M**0.61±0.33BH and Lcore∝L**0.79±0.30[O III]. Above MBH∼10**6.5 M⊙, accretion-driven processes dominate with Lcore∝M**1.5−1.65BH and Lcore∝L**0.99−1.31[O III] for active galaxies: radio-quiet/loud LINERs, Seyferts and jetted HII galaxies always display (although low) signatures of radio-emitting BH activity, with L1.5GHz≳10**19.8 W Hz−1 and MBH≳10**7 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 HII galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties.

Bibliographical metadata

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Publication statusAccepted/In press - 13 Sep 2021