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X-ray Diagnostics of Physical Conditions in Warm Absorbers
Y. Krongold (UNAM)
N. Brickhouse (CfA)M. Elvis (CfA)
F. Nicastro (CfA)S. Mathur (Ohio State U.)
D. Liedahl (LLNL)
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Found in the X-ray and UV spectra of 1/2 of all Seyfert 1 galaxies
Blueshifted (500-1000 km s-1) winds
mOUT maccr dynamically important
Valuable to understand quasars Interaction with ISM Metal pollution of the IGM
Warm Absorbers
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NGC 3783 Bright Seyfert galaxy redshift 0.0097
(2926 km s-1)
Extensively observed in the X-rays Monitored by the Chandra HETGS, Total exposure of 900 ksec > 2000 counts per resolution element at
7 A
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NGC 3783 Chandra MEG 900 ksec exposure
1keV
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Modeling with PHASE
Based on APED (Smith et al. 2001) accuracy in the wavelength
Plus data for inner shell transitions (Behar et al. 2001, 2002), and from Verner list
Ionization balance from CLOUDY Includes a Voigt Profiles Self Consistent Model Global Fit
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NGC 3783 Model
Photoionization Equilibrium Models
3 Free parameters per absorption component:
U =Q/4cr2n Ionization Parameter NH Column Density VOUT Outflow Velocity
2 Absorption Components
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NGC 3783 Chandra MEG 900 ksec exposure
1keV
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NGC 3783 Chandra MEG 900 ksec exposure
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Model Highlights
Simple solution only 2 absorbing components (LIP and HIP)
Fits more than 100 features with only 6 free parameters.
Predicts reasonable absorption in the UV by the LIP
Netzer et al. (2003) modeled a third hotter component (Fe K-shell, VHIP)
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Does not fit two significant LIP lines:
Si X, Si XI
Lack of low temperature (n=0) DR rates for Fe M-shell (Netzer et al. 2003; Netzer 2004; Kraemer Ferland and Gabel 2004)
Si X-XISi X-XI
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Other Representation Many Charge states present in the spectrum
Continuous Radial Flow of Ionization structures
Several charge states of the same element are significantly present
Not a global fit, but based on ion by ion Fits everything 40 free parameters Not self consistent
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Pressure Equilibrium
Similar kinematical properties
Confirmed by Netzer et al. (2003), plus 3erd component
3 phase medium
Phases of the same medium:
1/P
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Another Case of Pressure Balance: NGC 985
Pressure Equilibrium
Similar kinematical properties
Marginal evidence of 3rd component
3 phase medium?1/P
Krongold et al. 2004 , ApJ in press
80ksec exposure with Chandra HETGS
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Constraining the Structure and Location
of the Absorber
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Constraining the Structure of the Absorber
Continuous Flow
Several Charge States of the same element
Averaged absorption is observed
No response to flux variations by factors < 3-5
Clumped Gas
Should respond even to moderate flux variations
Isolated Components vary as expected in PI
U Flux
Opacity variation in response to flux variations
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Variability on NGC 3783 (LIP)
Bin size of 0.25 Å
Data Photoionization Equilibrium Model
Krongold et al. 2005, ApJ in press
2X flux increase
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The UTA varies as expected in PI
Data Ratio Model Ratio
Significance ~10
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Implications of Variability Variability observed in the UTA rules out a
Radial Continuous Flow of Ionization Stages If LIP in PI Using tobs as upper limit to recombination
time ne 104 cm-3
Using ne and U1/neD2 D < 6 pc (Reeves et al. 2004; Nicastro et al 1999; Netzer et al.
2002; Kriss and Blustin et al. 2003, Kaastra et al.2004)
ΔD < .15 pc Compact Absorber
Behar et al. (2003) D > 2 pc
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Further Constraints of the Density
Most Determinations are Upper or Lower Limits
We need to constrain the density ne to constrain D
Diagnostics of n:
Atomic Physics (Kaastra 2004)
Time Evolving Photoionization Models (Nicastro 1999)
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Constraining the Line Widths of the Absorber
Constraining the Geometry?
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The width of the Lines Absorption Lines are not Resolved
We have to constrain the width of the Lines indirectly
Through Models • (Widths > 200 km s-1)
Through UV data • (Widths between 100-200 km s-1)
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Voigt Profiles Convolution of Natural
and Doppler Broadening
Voigt Parameter a Γ/Δ
Not relevant in other bands
a << 1 Relevant in X-rays
a > 1(Inner shell Transitions) Affects the Depth at
the core of the line:
oNifulo
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oNifulo
Fe Inner Shell vs. Outer Shell
)(
)(
v
vOUTERo
INNERo
OUTERo
INNERo
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Constraining the GeometryUV data Constraints (Figure by Arav 2003)
UV widths >> X-ray widths UV widths ~ X-ray widths
UV
X-ray X-ray
Constraining the widths we can constrain the angle of the flow
TransverseFlow
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Conclusions WA can be modeled with a Simple picture Fits almost all absorption features with only few free
parameters
3 or 2 phases Observed in other objects
(NGC 5548, Kaastra et al 2002; IRAS 13349+2438, Sako et al. 2001, etc.) Intrinsic property related to the structure of the nuclear
environment of AGN
Pressure equilibrium (and similar kinematics) Suggests pressure confinement
Observed Variability
Rules out a Radial Continuous flow clumped gas Better Diagnostics in ne and D
Better Diagnostics of the widths Geometry Consistent with transverse flow (consistent with UV
observations)