Query : 2011A&A...534A.126P

2011A&A...534A.126P - Astronomy and Astrophysics, volume 534A, 126-126 (2011/10-1)

X-ray spectroscopy of the Compton-thick Seyfert 2 ESO 138-G1.


Abstract (from CDS):

We report on our analysis of XMM-Newton observations of the Seyfert 2 galaxy ESO 138-G1 (z=0.0091). These data reveal a complex spectrum in both its soft and hard portions. The 0.5-2keV band is characterized by a strong ``soft-excess'' component with several emission lines, as commonly observed in other narrow-line AGN. Above 3keV, a power-law fit yields a very flat slope (Γ∼0.35), along with the presence of a prominent line-like emission feature around ∼6.4keV. This indicates heavy obscuration along the line of sight to the nucleus. We find an excellent fit to the 3-10keV continuum with a pure reflection model, which provides strong evidence of a Compton-thick screen, preventing direct detection of the intrinsic nuclear X-ray emission. Although a model consisting of a power law transmitted through an absorber with NH∼2.5x1023cm–2 also provides a reasonable fit to the hard X-ray data, the equivalent width (EW) value of ∼800eV measured for the FeKα emission line is inconsistent with a primary continuum obscured by a Compton-thin column density. Furthermore, the ratio of 2-10keV to de-reddened [OIII] fluxes for ESO 138-G1 agrees with the typical values reported for well-studied Compton-thick Seyfert galaxies. Finally, we also note that the upper limits to the 15-150keV flux provided by Swift/BAT and INTEGRAL/IBIS seem to rule out the presence of a transmitted component of the nuclear continuum even in this very hard X-ray band, hence imply that the column density of the absorber could be as high as 1025cm–2. This makes ESO 138-G1 a very interesting, heavy Compton-thick AGN candidate for the next X-ray missions with spectroscopic and imaging capabilities above 10keV.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: nuclei - X-ray: galaxies - galaxies: individual: ESO 138-G1

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 ESO 138-1 Sy2 16 51 20.2687785665 -59 14 04.287486933   14.35 13.63 13.02   ~ 114 0
2 NGC 6221 Sy2 16 52 46.329 -59 13 00.99   10.90 13.45 9.68 10.4 ~ 284 0

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