LeMMINGs: V. Nuclear activity and bulge properties: A detailed multi-component decomposition of e -MERLIN Palomar galaxies with HST

B. T. Dullo, J. H. Knapen, R. J. Beswick, R. D. Baldi, D. R.A. Williams, I. M. McHardy, J. S. Gallagher, S. Aalto, M. K. Argo, A. Gil De Paz, H. R. Klöckner, J. M. Marcaide, C. G. Mundell, I. M. Mutie, P. Saikia

Research output: Contribution to journalArticlepeer-review


We used high-resolution HST imaging and e-MERLIN 1.5-GHz observations of galaxy cores from the LeMMINGs survey to investigate the relation between optical structural properties and nuclear radio emission for a large sample of galaxies. We performed accurate, multi-component decompositions of new surface brightness profiles extracted from HST images for 163 LeMMINGs galaxies and fitted up to six galaxy components (e.g. bulges, discs, AGN, bars, rings, spiral arms, and nuclear star clusters) simultaneously with Sérsic and/or core-Sérsic models. By adding such decomposition data for ten LeMMINGs galaxies from our past work, the final sample of 173 nearby galaxies (102 Ss, 42 S0s, 23 Es, plus six Irr) with a typical bulge stellar mass of M∗,bulge ~ 106 -1012.5 M⊙ encompasses all optical spectral classes: low-ionisation nuclear emission-line region (LINER), Seyfert, Absorption Line Galaxy (ALG), and H′ ¯II. We show that the bulge mass can be significantly overestimated in many galaxies when components such as bars, rings, and spirals are not included in the fits. We additionally implemented a Monte Carlo method to determine errors on the bulge, disc, and other fitted structural parameters. Moving (in the opposite direction) across the Hubble sequence, that is from the irregular to elliptical galaxies, we confirm that bulges become larger, more prominent, and round. Such bulge dominance is associated with a brighter radio core luminosity. We also find that the radio detection fraction increases with bulge mass. At M∗,bulge ≫ 1011 M⊙, the radio detection fraction is 77%, declining to 24% for M∗,bulge < 1010 M⊙. Furthermore, we observe that core-Sérsic bulges tend to be systematically round and to possess high radio core luminosities and boxy-distorted or pure elliptical isophotes. However, there is no evidence for the previously alleged strong tendency of galaxies'central structures (i.e. a sharp Sérsic, core-Sérsic dichotomy) with their radio loudness, isophote shape, and flattening.

Original languageEnglish
Article numberA105
JournalAstronomy and Astrophysics
Early online date6 Jul 2023
Publication statusPublished - 31 Jul 2023
Externally publishedYes

Bibliographical note

Funding Information:
We thank the anonymous referee for their careful reading of the manuscript and for their suggestions. We would like to thank Alex Rosenthal for the help with the 2D IMFIT decompositions of the HST images. B.T.D acknowledges support from grant ‘Ayudas para la realización de proyectos de I+D para jóvenes doctores 2019.’ for the HiMAGC (High-resolution, Multi-band Analysis of Galaxy Centres) project funded by Comunidad de Madrid and Universidad Complutense de Madrid under grant number PR65/19-22417. This work has been supported by the AEI-MCINN grant RTI2018-096188-B-I00. J.H.K. acknowledges financial support from the State Research Agency (AEI-MCINN) of the Spanish Ministry of Science and Innovation under the grant ‘The structure and evolution of galaxies and their central regions’ with reference PID2019-105602GB-I00/10.13039/501100011033, from the ACIISI, Consejería de Economía, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference PROID2021010044, and from IAC project P/300724, financed by the Ministry of Science and Innovation, through the State Budget and by the Canary Islands Department of Economy, Knowledge and Employment, through the Regional Budget of the Autonomous Community. JSG thanks the University of Wisconsin-Madison for partial support of this research. CGM acknowledges financial support from Jim and Hiroko Sherwin. Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA). We would like to acknowledge the support from the e-MERLIN Legacy project ‘LeMMINGs’, upon which this study is based. e-MERLIN, and formerly, MERLIN, is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of the STFC. We acknowledge Jodrell Bank Centre for Astrophysics, which is funded by the STFC. This work has made use of NUMPY (van der Walt et al. 2011), MATPLOTLIB (Hunter 2007) and CORNER (Foreman-Mackey 2016) and ASTROPY , a community-developed core PYTHON package for Astronomy (Astropy Collaboration 2013, 2018), and of TOPCAT (i.e. ‘Tool for Operations on Catalogues And Tables’, Taylor 2005). The data underlying this article are available in the article and in its online supplementary material.


  • CD
  • Galaxies: elliptical and lenticular
  • Galaxies: nuclei
  • Galaxies: photometry
  • Galaxies: spiral
  • Galaxies: structure
  • Radio continuum: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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