An X-ray view of 82 LINERs with Chandra and XMM-Newton data

TL;DR

This study provides a comprehensive X-ray spectral analysis of 82 LINERs, revealing that about 80% host active galactic nuclei, and introduces models with double absorbers to better understand their nuclear properties.

Contribution

It offers the largest homogeneous X-ray spectral dataset for LINERs, incorporating new models with double absorbers and multiwavelength data for improved AGN identification.

Findings

80% of LINERs show evidence of AGN activity

Spectral fits favor composite models with absorbed continuum and soft components

Majority exhibit compact nuclear X-ray sources indicating active nuclei

Abstract

We present the results of an homogeneous X-ray analysis for 82 nearby LINERs selected from the catalogue of Carrillo et al. (1999). All sources have available Chandra (68 sources) and/or XMM-Newton (55 sources) observations. This is the largest sample of LINERs with X-ray spectral data (60 out of the 82 objects) and significantly improves our previous analysis based on Chandra data for 51 LINERs (Gonzalez-Martin et al. 2006). It increases both the sample size and adds XMM-Newton data. New models permit the inclusion of double absorbers in the spectral fits. Nuclear X-ray morphology is inferred from the compactness of detected nuclear sources in the hard band (4.5-8.0 keV). Sixty per cent of the sample shows a compact nuclear source and are classified as AGN candidates. The spectral analysis indicates that best fits involve a composite model: absorbed primary continuum and (2) soft spectrum below 2 keV described by an absorbed scatterer and/or a thermal component. The resulting median spectra parameters and their standard deviations are: G=2.11, <kT>=0.54 keV, <log(NH1)>=21.32 and <log(NH2)>=21.93. We complement our X-ray results with our analysis of HST optical images and literature data on emission lines, radio compactness and stellar population. Adding all these multiwavelength data, we conclude that evidence do exist supporting the AGN nature of their nuclear engine for 80% of the sample (66 out of 82 objects).