Advection-dominated accretion, jets and the spectral energy distribution of LINERs

TL;DR

This study models the spectral energy distributions of LINERs, a type of low-luminosity AGN, revealing the roles of advection-dominated accretion flows and jets in their emission across multiple wavelengths.

Contribution

It introduces a coupled accretion-jet model for LINERs, demonstrating how jets and ADAFs contribute to their multiwavelength emission and estimating key physical parameters.

Findings

Radio emission is explained by jets, not ADAFs.

X-ray emission can originate from ADAF, jet, or both.

Model estimates of accretion and jet parameters are provided.

Abstract

Low-luminosity active galactic nuclei (LLAGNs) represent the bulk of the AGN population in the present-day universe and they trace low-level accreting supermassive black holes. The observational properties of LLAGNs suggest that their central engines are intrinsically different from those of more luminous AGNs. It has been suggested that accretion in LLAGNs occurs via an advection-dominated accretion flow (ADAF) associated with strong jets. In order to probe the accretion physics in LLAGNs as a class, we model the multiwavelength spectral energy distributions (SEDs) of 24 LINERs (taken from a recent compilation by Eracleous et al.) with a coupled accretion-jet model. The accretion flow is modeled as an inner ADAF outside of which there is a truncated standard thin disk. These SEDs include radio, near-IR to near-UV HST data, and Chandra X-ray data. We find that the radio emission is severely underpredicted by ADAF models but can be explained by the relativistic jet. The origin of the X-ray radiation in most sources can be explained by three distinct scenarios: the X-rays can be dominated by emission from the ADAF, the jet, or from both components contributing at similar levels. From the model fits, we estimate important parameters of the central engine of LINERs, such as the mass accretion rate -- relevant for studies of the feeding of AGNs -- and the mass-loss rate in the jet and the jet power -- relevant for studies of the kinetic feedback from jets.