The ionization structure of the wind in NGC 5548

1
The ionization structure of the wind in NGC 5548

• Katrien Steenbrugge
• Harvard-Smithsonian Center for Astrophysics
• In collaboration with Jelle Kaastra
• N. Arav, M. Crenshaw, S. Kraemer, R. Edelson, C.
  de Vries, I. George, D. Liedahl, R. van der Meer,
  F. Paerels, J. Turner, T. Yaqoob

2
Overview

• Introduction
• Open questions
• UV spectra and results
• X-ray spectra
• Ionization structure
• Geometry of the wind
• Mass loss through the wind
• Conclusions

3
NGC 5548

• Well studied nearby Seyfert 1 galaxy
• Low Galactic absorption
• X-ray bright
• Has a rather strong warm absorber
• Collision 0.6-1.0 Gyr ago (Tyson et al.1998, ApJ,
  116, 102)
• Study the core

4
Seyfert galaxies
NGC 5548, Kaastra et al. 2002

• Low luminosity AGN
• Broadened emission lines in optical and UV
  spectra
• Seyfert 1 broad and narrow lines
• X-ray Absorption spectrum
• Seyfert 2 broad lines in polarized
  light
• X-ray Emission line spectrum
  

NGC 1068, Kinkhabwala 2002
5
Geometry of the absorber

• Narrow and broad emission/absorption lines
• Viewing angle and unification
• Seyfert 2 edge on
• Seyfert 1 face on
• Urry Padovani, 1995, PASP, 107, 803

6
Geometry of the absorber

• 
  Elvis, 2000, ApJ, 545, 63

No absorption
BAL
NAL
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Similarities between models

• Elvis, 2000, ApJ, 545, 63

Clouds in pressure equilibrium with a hot outflow
8
Differences between models

• Difference in viewing angle
• Difference in opening angle of the outflow
• Difference in location of the absorber
• Explains Seyfert 1 galaxies without absorption
• Explains broad absorption line quasars
• Expect only 1 outflow velocity
• Explains IR emission
• Explains Seyfert 2 galaxies

9
Open questions

• Are the absorbers seen in the UV and the X-rays
  the same (Mathur, Wilkes Elvis, 1995, ApJ, 452,
  230)
• Ionization structure of the absorber
• Location and geometry of the absorber
• Mass loss through wind, enrichment IGM

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Photo-ionized plasma

• Strong radiation field
• Low density gas
• Plasma is ionized by absorbing photons
• Gives specific triplet ratios and series line
  ratios
• Optically thin ? ignore radiative transfer

Godet, Collin Dumnont, 2004
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Ionization parameter

• ? L/nr2
• L luminosity
• n gas density
• r distance from source

12
XMM-Newton

• RGS (7-38 ?)
• spectral resolution 0.07 ? FWHM
• EPIC MOS
• EPIC pn
• Large effective area
• Simultaneous observations

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Chandra

• HETGS (1-24 ?)
• LETGS ( 1-180 ?)
• Spectral resolution between 0.012 ? and 0.05 ?
• Long wavelength range
• Low effective area
• Non-simultaneous observations

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Observational campaign
RGS 137 ks July 2001

• Simultaneous UV and X-ray observations

HETGS 170 ks Jan. 2002
LETGS 340 ks Jan. 2002
HST STIS 21 ks Jan. 2002
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UV spectra

• Broad emission lines FWHM8000 km/s
• Narrow emission lines FWHM1000 km/s
• Absorption lines FWHM100 km/s
• 5 ? outflow v
• Lowly ionized absorber
• Arav et al. 2001, 2003, Crenshaw et al. 2003,
  Brotherton et al. 2002

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Absorption components
Outflow velocity FWHM Log NC IV Log NN V
166 km/s 61 km/s 17.76 m-2 18.16 m-2
336 km/s 145 km/s 18.43 m-2 18.86 m-2
530 km/s 159 km/s 17.97 m-2 18.94 m-2
667 km/s 43 km/s 17.75 m-2 18.16 m-2
1041 km/s 222 km/s 18.05 m-2 18.44 m-2
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UV spectra dusty absorber

• Fit 1 ionization parameter per velocity component
• In order that all 4 lines fit play around with
  abundances
• Abundance ratios could be explained if some C,
  Mg, Si and Fe are stored in dust

C 0.35
N 1
O 0.75
Mg 0.2
Si 0.06
Fe 0.05
But multiple ionization parameters per
velocity component !
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UV spectra results

• Crenshaw et al. 2003
• Dusty absorber
• log NOVI20.26 m-2
• log NOVIII20.20 m-2
• Arav et al. 2002,2003
• FUSElog NOVI19.69 m-2
• Non-black saturation
• Lower limit to column density

19
X-ray spectra

• Combine HETGS resolution with ? range LETGS
• Probe low to highly ionized absorber

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Are the absorbers seen in the UV and the X-rays
the same ?
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Velocity structure

• Resolve the highest UV outflow v for 6 ions
• Same outflow velocity structure as the UV

22
Ionization parameter

• Detect O VI and lower ionized ions
• log NO VI20.6 m-2
• Inferred NH 1024 m-2
• Order of magnitude more than detected in UV

23
Comparison

• Same velocity structure, same ionization
• Different column densities
• Possible solution (Arav et al. 2002)
• The absorber does not cover the NELs
• ? Non-black saturation, underestimate NH
• Velocity dependent covering factor in the UV
• UV and X-ray absorber are the same

24
Velocity structure

• If we measure 1 outflow v
• Higher ionized ions have higher outflow
  velocities

25

• Ionization structure of velocity components

HST STIS
FUSE
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Ionization structure of the absorber

• Both models require clouds in pressure
  equilibrium.
• Pressure equilibrium implies several separate
  components with a different ionization parameter.

27
Ionization structure

• Iron is best indicator of ionization
• H abundance 10
• Lower ionized iron ionization is uncertain
• (Netzer et al. 2003)

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Ionization structure

• RGS data
• Fe only
• Model with 3,4 and 5 ionization components

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Pressure equilibrium

• ? L/ (4pcr2P)
• 0.961x104 ?/T
• L luminosity, r distance
• c speed of light
• P ideal gas pressure
• P nkT
• T temperature
• In ? versus T plot means vertical section
  constant nT

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Ionization structure

• Are the different ionization states in pressure
  equilibrium?

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Continuous ionization distribution

• Assume solar abundances
• Continuous distribution over 3.5 orders in
  ?
• dNH/dln??a
• a0.400.05

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Spectral variability low state

• New observation
• March 15 2005
• Low hard state
• Preliminary results
• M. Fenovcík

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Spectral variability low state

• Stronger OV, O III
• Noisy O IV
• Column density of O VI, O VII and O VIII did not
  vary
• Supports continuum ionization model
• Hard to explain in clouds in pressure equilibrium
  model

Marian Fenovcík, in prep.
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Spectral variability NGC 3783
RGS
EPIC pn

• Higher ? absorber is variable, while low ? is not
  in NGC 3783 XMM data
• (Behar et al. 2003, Reeves et al. 2004)

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Geometry of the absorber
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Geometry of the wind
v (km/s) -166 -1040
?1 0.0007 0.0001
?1000 0.7 0.1
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Geometry of the absorber

• Narrow streams
• Dense core lowly ionized
• One stream per outflow velocity component
  observed
• Gives asymmetric line profile

Arav et al., 1999, ApJ, 516, 27
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Can mass escape?

• Important for the enrichment of the IGM and AGN
  feedback
• vesc (2GMBH/r)1/2
• MBH 6.8 107 Mo (Wandel 2002)
• v 166 km/s to 1041 km/s
• r (5.8/vr2) 105 pc
• Assuming vr 1000 km/s ?r 0.6 pc
• Assuming all mass escapes and mass loss mass
  accretion Mloss 0.3 M0/yr

39
Broad emission lines

• Very weak
• O VII triplet
• Expected from optical and UV ionization

40
Future work
Has the ionization a cut-off, or is most of the
gas completely ionized?
ASTROE-2 Launch summer 2005 High resolution high
energy grating Study the highly ionized universe
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Conclusions

• The UV and X-ray absorbers are the same
• The absorbers are not in pressure equilibrium
• The ionization structure is likely continuous
  spanning 3.5 orders in ?
• The outflow occurs in narrow steamers
• Likely, part of the outflow escapes