The Astrophysical Journal | VOL. 704


Publication Date Oct 20, 2009


In this paper, we study the nuclear obscuration of galaxies hosting low ionization narrow emission regions (LINERs) based on their X-ray and optical emission. They show column densities at soft energies (0.5-2 keV) mostly related to the diffuse emission around the active galactic nucleus (AGN), showing a correlation with the optical extinction. Column densities at hard energies (2-10 keV) seem to be much higher than what would be expected from the optical extinction. They might be associated with the inner regions of the AGN, buried at optical wavelengths. The main result of this paper is that around 50% of our LINER sample shows signatures of Compton-thickness according to the most common tracers: the X-ray spectral index, F{sub X}(2-10 kV)/F([o{sub III}]) ratio, and FeKalpha equivalent width (EW). However, the EWs of the Compton-thick LINERs are significantly lower than in the Compton-thick Seyferts (approx =200 eV against >=500 eV), suggesting that the 2-10 keV emission is dominated by electron scattering of the otherwise invisible AGN, or by emission from shocked gas associated with star formation rather than by reflection from the inner wall of the torus. However, no clear relation seems to exist between galaxies with optical dust lanes and X-ray classifiedmore » Compton-thick objects. This may suggest that Compton-thick sources should be related to absorbing material located at the very inner regions of the AGN, maybe in the putative dusty torus. Larger black hole masses and lower Eddington ratios than Seyfert galaxies...

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Active Galactic Nucleus
Compton-thick Sources
Larger Black Hole Masses
Optical Extinction
Lower Eddington Ratios
X-ray Spectral Index
Earlier Morphological Types
Equivalent Width
Compton-thick Objects
Common Tracers

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