Abstract
Seyfert galaxies, local Active Galactic Nuclei (AGN), contain a nuclear
accreting supermassive black hole surrounded by a torus of dust and gas.
In Type 2 Seyfert galaxies (Sy2s) this systems is oriented such that the
line of sight is through the obscuring torus, blocking the accretion
disk and broad line region from view. When the column density of the
torus exceeds 1.5 x 1024 cm-2, the source becomes
"Compton-thick." Several proxies of intrinsic AGN luminosity do,
however, exist: emission from gas formed in the narrow line region
(which extends hundreds of parsecs above and below the torus), such as
the [OIII] 5007 Angstrom and [OIV] 25.89 micron line, and infrared
emission from the torus itself. A sample of Seyfert galaxies selected
based on such isotropic diagnostics would therefore not be biased by the
amount of obscuration present in the system. Subsequent X-ray
observations can then be used to estimate the Compton-thick population
as X-ray emission forms in a halo around the accretion disk and is thus
subject to torus obscuration.
We present the X-ray analysis of two homogeneous samples of Sy2s,
selected based on isotropic indicators of AGN luminosity: one selected
from the Sloan Digital Sky Survey based on a high observed [OIII] flux,
and the other drawn from the original IRAS 12-micron sample. We estimate
the fraction of Compton-thick sources in these two complementary samples
by comparing the X-ray luminosity to various intrinsic AGN luminosity
proxies and by spectral signatures of reprocessing, such as the
equivalent width of the Fe K-alpha line. We estimate the amount of
obscuration present in these systems and compare them to the column
density derived from spectral fits. Finally, we search for correlations
between host galaxy properties and Compton-thick diagnostics to
investigate whether these obscured sources trace a unique host galaxy
population.
Original language | English |
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Pages | 657-657 |
Publication status | Published - 2010 |
Event | American Astronomical Society, 11th HEAD meeting - Waikoloa Village, Big Island, Hawaii, United States Duration: 1 Mar 2010 → 4 Mar 2010 |
Conference
Conference | American Astronomical Society, 11th HEAD meeting |
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Country/Territory | United States |
City | Waikoloa Village, Big Island, Hawaii |
Period | 1/03/10 → 4/03/10 |