Evidence for the AGN nature of LINERs

González-Martín, O.; Masegosa, J.; Márquez, I.; Jiménez-Bailón, E.
Bibliographical reference

Black Holes from Stars to Galaxies -- Across the Range of Masses. Edited by V. Karas and G. Matt. Proceedings of IAU Symposium #238, held 21-25 August, 2006 in Prague, Czech Republic. Cambridge, UK: Cambridge University Press, 2007., pp.373-374

Advertised on:
4
2007
Number of authors
4
IAC number of authors
0
Citations
1
Refereed citations
1
Description
Low-luminosity AGNs (LLAGNs), which make up the vast majority of the AGN population, may yield important clues into the origin and evolution of nuclear activity, constituting a perfect laboratory to investigate the connection between galaxies in which the central black holes are active and those in which they are quiescent. The precence of a compact X-ray nucleus may provide evidences about their AGN nature. Chandra's excellent resolution allows an investigation of the X-ray nuclear properties of these galaxies. Low Ionization Nuclear-Emission Ragions (LINERs) have been selected from the catalogue by Carrillo et al. (1999). Data on 51 out of the initial 495 optical LINERs are found with the required signal-to-noise. The X-ray morphology has been classified attending to their nuclear compactness in the hard band (4.5-8 keV) into 2 categories: AGN-like nuclei (those with a clearly identified unresolved nuclear source) and Starburst-like nuclei (the ones without a clear nuclear source). 59% of the total sample are classified as AGNs with a median luminosity of 2.5x 1040 erg/s, which is an order of magnitude greather than for SB-like nuclei. The spectral fitting implies that most of the objects need a non-negligible contribution from a non-thermal component. Color-Color diagrams are defined which allow us to compute physical parameters to analyze the origin of the X-ray emission. This method is specially useful for galaxies with low S/N for which no spectral fitting can be performed. The presence of an AGN seems to be the most natural explanation for the origin of the power-law component. A comparative sample of Seyfert 2 objects has been compiled from Chandra archive, to look for common properties or eventual differences between both AGN populations.