Dullo, B.T., Knapen, J.H., Baldi, R.D., Williams, D.R.A., Beswick, R.J., McHardy, I.M., Green, D.A., Paz, A. Gil de, Aalto, S., Alberdi, A., Argo, M.K., Gallagher, J.S., Klöckner, H.-R., Marcaide, J.M., Mutie, I.M., Saikia, D.J., Saikia, P., Stevens, I.R. and Torrejón, S. (2024) LeMMINGs. Multi-wavelength constraints on the co-existence of nuclear star clusters and AGN in nucleated galaxies. Monthly Notices of the Royal Astronomical Society, 532 (4), 4729-4751. (doi:10.1093/mnras/stae1732).
Abstract
The relation between nuclear star clusters (NSCs) and the growth of the central supermassive black holes (SMBHs), as well astheir connection to the properties of the host galaxies, is crucial for understanding the evolution of galaxies. Recent observationshave revealed that about 10 per cent of nucleated galaxies host hybrid nuclei, consisting of both NSCs and accreting SMBHsthat power active galactic nuclei (AGNs). Motivated by the potential of the recently published multiwavelength data sets fromLeMMINGs survey, here we present the most thorough investigation to date of the incidence of hybrid nuclei in a large sample of100 nearby nucleated galaxies (10 E, 25 S0, 63 S, and 2 Irr), covering a wide range in stellar mass (M∗,gal ∼ 108.7 − 1012 M⨀).We identify the nuclei and derive their properties by performing detailed 1D and 2D multicomponent decompositions of theoptical and near-infrared HST stellar light distributions of the galaxies using Sersic ´ and core-Sersic ´ models. Our AGN diagnosticsare based on homogeneously derived nuclear 1.5 GHz e-MERLIN radio, Chandra X-ray (0.3–10 keV), and optical emission-linedata. We determine the nucleation fraction (fnuc) as the relative incidence of nuclei across the LeMMINGs HST sample and find fnuc = 100/149 (= 67 ± 7 per cent), confirming previous work, with a peak value of 49/56 (= 88 ± 13 per cent) at bulge masses M∗,bulge ∼ 109.4 − 1010.8 M⨀. We identify 30 nucleated LeMMINGs galaxies that are optically active, radio-detected, and X-rayluminous (LX > 1039 erg s−1). This indicates that our nucleated sample has a lower limit ∼ 30 per cent occupancy of hybridnuclei, which is a function of M∗,bulge and M∗,gal. We find that hybrid nuclei have a number density of (1.5 ± 0.4) × 10−5 Mpc−3,are more common at M∗,gal ∼ 1010.6 − 1011.8 M⨀ and occur, at least, three times more frequently than previously reported.
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