302 research outputs found
Uncovering Local Absorbed Active Galactic Nuclei with Swift and Suzaku
Detection of absorbed active galactic nuclei and their properties remains an
elusive and important problem in understanding the evolution and activation of
black holes. With the very hard X-ray survey conducted by Swift's Burst Alert
Telescope - the first all-sky survey in 30 years - we are beginning to uncover
the characteristics of obscured AGN. The synergy between Suzaku and Swift has
been crucial in pinning down the X-ray properties of newly detected heavily
obscured but bright hard X-ray sources. We review the X-ray and optical
spectroscopic properties of obscured AGN in the local Universe, as detected in
the Swift survey. We discuss the relative distribution of absorbed/unabsorbed
sources, including "hidden" and Compton thick AGN populations. Among the
results from the survey, we find that absorbed AGN are less luminous than
unabsorbed sources. Optical spectra reveal that sources with emission line
ratios indicative of LINERs/H II galaxies/composites are the least luminous
objects in the sample, while optical absorbed and unabsorbed Seyferts have the
same luminosity distributions. Thus, the least luminous sources are likely
accreting in a different mode than the Seyferts.Comment: 8 pages, 5 figures, To appear in the conference proceedings for
"Exploring the X-ray Universe: Suzaku and Beyond", the July 2011 Suzaku
Science Conferenc
The Complex X-ray Spectrum of the Sefyert 1.5 Source NGC 6860
The X-ray spectrum of the Seyfert 1.5 source NGC 6860 is among the most
complex of the sources detected in the Swift Burst Alert Telescope all-sky
survey. A short XMM-Newton follow-up observation of the source revealed a flat
spectrum both above and below 2 keV. To uncover the complexity of the source,
in this paper we analyze both a 40 ks Suzaku and a 100 ks XMM-Newton
observation of NGC 6860. While the spectral state of the source changed between
the newer observations presented here and the earlier short XMM-Newton spectrum
- showing a higher flux and steeper power law component - the spectrum of NGC
6860 is still complex with clearly detected warm absorption signatures. We find
that a two component warm ionized absorber is present in the soft spectrum,
with column densities of about 10^20 and 10^21 cm$^-2, ionization parameters of
xi = 180 and 45 ergs cm s^-1, and outflow velocities for each component in the
range of 0-300 km s^-1. Additionally, in the hard spectrum we find a broad
(approx 11000 km s^-1) Fe K-alpha emission line, redshifted by approx 2800 km
s^-1.Comment: 35 pages, 9 figures, Accepted to Ap
The Swift BAT Survey Detects Two Optical Broad Line, X-ray Heavily Obscured Active Galaxies: NVSS 193013+341047 and IRAS 05218-1212
The Swift Burst Alert Telescope (BAT) is discovering interesting new objects
while monitoring the sky in the 14-195 keV band. Here we present the X-ray
properties and spectral energy distributions for two unusual AGN sources. Both
NVSS 193013+341047 and IRAS 05218-1212 are absorbed, Compton-thin, but heavily
obscured (NH \sim 10^23 cm-2), X-ray sources at redshifts < 0.1. The spectral
energy distributions reveal these galaxies to be very red, with high extinction
in the optical and UV. A similar SED is seen for the extremely red objects
(EROs) detected in the higher redshift universe. This suggests that these
unusual BAT-detected sources are a low- redshift (z << 1) analog to EROs, which
recent evidence suggests are a class of the elusive type II quasars. Studying
the multi-wavelength properties of these sources may reveal the properties of
their high redshift counterparts.Comment: 20 pages, accepted to Ap
Optical Spectral Properties of Swift BAT Hard X-ray Selected Active Galactic Nuclei Sources
The Swift Burst Alert Telescope (BAT) survey of Active Galactic Nuclei (AGN)
is providing an unprecedented view of local AGNs ( = 0.03) and their host
galaxy properties. In this paper, we present an analysis of the optical spectra
of a sample of 64 AGNs from the 9-month survey, detected solely based on their
14-195 keV flux. Our analysis includes both archived spectra from the Sloan
Digital Sky Survey and our own observations from the 2.1-m Kitt Peak National
Observatory telescope. Among our results, we include line ratio classifications
utilizing standard emission line diagnostic plots, [O III] 5007 A luminosities,
and H-beta derived black hole masses. As in our X-ray study, we find the type 2
sources to be less luminous (in [O III] 5007 A and 14-195 keV luminosities)
with lower accretion rates than the type 1 sources. We find that the optically
classified LINERs, H II/composite galaxies, and ambiguous sources have the
lowest luminosities, while both broad line and narrow line Seyferts have
similar luminosities. From a comparison of the hard X-ray (14-195 keV) and [O
III] luminosities, we find that both the observed and extinction-corrected [O
III] luminosities are weakly correlated with X-ray luminosity. In a study of
the host galaxy properties from both continuum fits and measurements of the
stellar absorption indices, we find that the hosts of the narrow line sources
have properties consistent with late type galaxies.Comment: 84 pages, 20 figures, 17 tables, accepted in Ap
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