Evidence of Parsec-Scale Jets in Low-Luminosity Active Galactic Nuclei

Abstract

The nuclear radio emission of low-luminosity active galactic nuclei (LLAGN) is often associated with unresolved cores. In this paper we show that most LLAGN present extended jet radio emission when observed with sufficient angular resolution and sensitivity. They are thus able to power, at least, parsec-scale radio jets. To increase the detection rate of jets in LLAGN, we analyze subarcsecond resolution data of three low-ionization nuclear emission regions. This yields the detection of extended jet-like radio structures in NGC 1097 and NGC 2911 and the first resolved parsec-scale jet of NGC 4594 (Sombrero). The three sources belong to a sample of nearby LLAGN for which high-spatial-resolution spectral energy distribution of their core emission is available. This allows us to study their accretion rate and jet power (Q jet ) without drawing on (most) of the ad hoc assumptions usually considered in large statistical surveys. We find that those LLAGN with large-scale radio jets (>100 pc) have Q jet > 10 42 erg s −1 , while the lowest Q jet correspond to those LLAGN with parsec-scale (≤100 pc) jets. The Q jet is at least as large as the radiated bolometric luminosity for all LLAGN, in agreement with previous statistical studies. Our detection of parsec-scale jets in individual objects further shows that the kinematic jet contribution is equally important in large-or parsec-scale objects. We also find that the Eddington-scaled accretion rate is still highly sub-Eddington (< 10 −4 ) when adding the Q jet to the total emitted luminosity (radiated plus kinetic). This indicates that LLAGN are not only inefficient radiators but that they also accrete inefficiently or are very efficient advectors.

A new period of activity in the core of NGC 660

“…in M51 Rampadarath et al in prep; more generally in Nagar et al 2002Nagar et al , 2005Panessa & Giroletti 2013;Mezcua & Prieto 2014). In NGC 660, the central source detected by e-MERLIN is both compact and flat spectrum, and the EVN map shows evidence of a core-jet structure.…”

A refined sub-grid model for black hole accretion and AGN feedback in large cosmological simulations

“…Recently, Mezcua & Prieto (2014) presented measurements of luminosities of a much smaller sample of AGN, but with sufficiently larger angular resolution and sensitivity. Their estimations for L bol are more reliable than those presented in Russell et al (2013), because they measure L bol after integrating the radio to X-ray Spectral Energy Distribution (SED).…”

“…There is evidence for two distinct phases of AGN activity and feedback: the radio-mode and the quasar-mode. The radio-mode is characterized by large radio jets generating hot X-ray cavi-E-mail: steinborn@usm.lmu.de ties (Russell et al 2013, Mezcua & Prieto 2014, whereas in the quasar-mode the emission is dominated by the accretion disc, which is visible as the so-called blue bump in the spectrum of quasars and Seyfert galaxies (e.g. Elvis et al 1994, Prieto et al 2010).…”

Kinetic and radiative power from optically thin accretion flows

“…Several studies aiming at comparing the radiative and kinetic properties have been recently performed (e.g., King et al 2012;Mezcua & Prieto 2014;Hlavacek-Larrondo et al 2015;Hogan et al 2015;Shin et al 2016) In this work, we mainly use results by Russell et al (2013), one of the most comprehensive investigations based on observations of nuclear X-ray sources and the corresponding cavities in a large sample of 57 BCGs. These authors have found that the nuclear radiation exceeds the mechanical energy output of the outflow when the mean accretion rate rises above a few percent of the Eddington luminosity, corresponding to the onset of the quasar mode.…”