Publication details

Radio Emission of Nearby Early-type Galaxies in the Low and Very Low Radio Luminosity Range


WÓJTOWICZ Anna Patrycja STAWARZ Łukasz CHEUNG C. C. WERNER Norbert RUDKA Dominik

Year of publication 2023
Type Article in Periodical
Magazine / Source Astrophysical Journal
MU Faculty or unit

Faculty of Science

Keywords Radio active galactic nuclei; Radio galaxies; Radio cores; Early-type galaxies; Radio jets
Description We analyze radio continuum emission of early-type galaxies with dynamical measurements of central supermassive black hole (SMBH) masses and well-characterized large-scale environments, but regardless of the exact level of the nuclear activity. The 1.4 GHz radio fluxes collected with ~arcmin resolution for 62 nearby targets (distances ?153 Mpc) correspond to low and very low monochromatic luminosities of Lr ~ 1035–1041 erg s-1. We quantify possible correlations between the radio properties with the main parameters of SMBHs, host galaxies, and hot gaseous halos, finding a general bimodality in the radio luminosity distribution, with the borderline between radio-bright and radio-dim populations at $\mathrm{log}{L}_{{\rm{r}}}/{L}_{\mathrm{Edd}}\simeq -8.5$. We analyze the far-infrared data for the targets, finding that all radio-bright and over a half of the radio-dim sources are overluminous in radio wavelengths with respect to the far-infrared–radio correlation. High-resolution radio maps reveal that the overwhelming majority of radio-dim sources is unresolved on the arcsecond scale, while the bulk of radio-bright sources display extended jets and lobes of low- and intermediate-power radio galaxies; these jets dominate the radio emission of radio-bright objects. Regarding the origin of the radio emission of radio-dim sources, we discuss two main possibilities. One possibility is the advection-dominated accretion flow model, in which the radio and nuclear X-ray radiative outputs at very low accretion rates are both dominated by unresolved jets. The other possibility is that the radio-dim sources, unlike the radio-bright ones, are characterized by low values of SMBH spins, so that their radio emission is not related to the jets, but instead is due to a combination of star-forming processes and previous nuclear outbursts.
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