Abstract
Abstract Radio emission from the high- and super-Eddington accreting active galactic nuclei (AGNs) has various origins: a persistent jet, the magnetized corona, and the wind-like outflows. It is still unclear which is the leading mechanism responsible for the observed radio emission and how the radio emission is related to other characteristic parameters such as the Eddington ratio and black hole mass. In this paper, we present the 5 GHz Very Large Array (VLA) observational results of a sample of 25 extremely high Eddington accreting supermassive black holes (EESBHs, the Eddington ratio λ Edd close to or above 1) in narrow-line Seyfert 1 galaxies, among which 22 sources are detected. Most of the EESBHs show a compact radio structure from a few hundred parsecs to 1 kpc scale. We estimated the lowest star formation rate surface density required for producing the observed radio emission and found that it is higher than the largest value previously detected in circumnuclear starburst galaxies, implying that the radio emission is from the AGN activity. Along with a comparison sample, we find an overall inverse –λ Edd correlation ranging from sub- to super-Eddington ratios. The high-Eddington and mildly super-Eddington AGNs (−0.5 < log ) have a radio-to-X-ray luminosity ratio L R/L X ∼ 10−5–10−4 and a steep radio spectrum, supporting that the radio emission is from transient ejecta (outflows) of corona; however, the jet contribution cannot be entirely ruled out. Our highly super-Eddington sources (log ) have a flatter radio spectrum, along with its low radio luminosity: ; their radio emission is likely dominated by a magnetized corona, and a radiation-pressure-caused jet is also proposed in this paper.
Highlights
With increasing observational evidence during the past two decades, it is widely accepted that supermassive black holes (SMBHs) with MBH ~ 105-10 M reside at the centers of most galaxies
To study the super-Eddington accretion and investigate the origin of the radio emission in extremely high Eddington ratio accreting active galactic nucleus (AGN), we present high-resolution Very Large Array (VLA) results of a sample of narrow-line Seyfert 1 galaxies (NLS1s) that are accreting at Eddington ratios close to or exceeding 1
The new results for 25 Eddington ratio accreting supermassive black holes (EESBHs) observed with the VLA are obtained from a total of 45 data sets, of which 26 were previously published (see the references in Column (10) of Table 2), and the remaining 19 data sets are analyzed in this work
Summary
With increasing observational evidence during the past two decades, it is widely accepted that supermassive black holes (SMBHs) with MBH ~ 105-10 M reside at the centers of most galaxies (see review in Kormendy & Ho 2013). The total energy radiated by this process cannot exceed the Eddington luminosity for the spherically symmetric accretion, which was thought to be the main mechanism for regulating the growth of SMBHs. observations have shown that super-Eddington accretion can occur in a variety of celestial systems, such as Galactic X-ray binaries (XRBs), e.g., SS 433 (Gies et al 2002; Begelman et al 2006; Fabrika et al 2015; Middleton et al 2018) and GRS 1915+105 (Mirabel & Rodríguez 1994; Greiner et al 2001); tidal disruption events
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