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 Gyr ago (Tyson et al.1998, ApJ, 116, 102)
Study the core

4. Seyfert galaxies Low luminosity AGN
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

7. 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

10. 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

11. Ionization parameter ξ = L/nr2 L luminosity n gas density
r distance from source

12. XMM-Newton RGS (7-38 Ǻ) spectral resolution 0.07 Ǻ FWHM EPIC MOS
EPIC pn
Large effective area
Simultaneous observations

13. Chandra HETGS (1-24 Ǻ) LETGS ( 1-180 Ǻ)
Spectral resolution between Ǻ and 0.05 Ǻ
Long wavelength range
Low effective area
Non-simultaneous observations

14. Observational campaign
RGS
137 ks
July 2001
Simultaneous UV and X-ray observations:
HETGS
170 ks
Jan. 2002
LETGS
340 ks
HST STIS
21 ks

15. UV spectra Broad emission lines FWHM~8000 km/s
Narrow emission lines FWHM~1000 km/s
Absorption lines FWHM~100 km/s
5 ≠ outflow v
Lowly ionized absorber
Arav et al. 2001, 2003, Crenshaw et al. 2003, Brotherton et al. 2002

16. 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
1041 km/s
222 km/s
18.05 m-2
18.44 m-2

17. 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 !

18. UV spectra: results Crenshaw et al. 2003: Dusty absorber
log NOVI=20.26 m-2
log NOVIII=20.20 m-2
Arav et al. 2002,2003:
FUSE:log NOVI=19.69 m-2
Non-black saturation
Lower limit to column density

19. X-ray spectra Combine HETGS resolution with λ range LETGS
Probe low to highly ionized absorber

20. Are the absorbers seen in the UV and the X-rays the same ?

21. Velocity structure Resolve the highest UV outflow v for 6 ions
Same outflow velocity structure as the UV

22. Order of magnitude more than detected in UV
Ionization parameter
Detect O VI and lower ionized ions
log NO VI=20.6 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 NEL’s
→ 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

26. 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)

28. Ionization structure RGS data Fe only
Model with 3,4 and 5 ionization components

29. Pressure equilibrium Ξ = L/ (4πcr2P) = 0.961x104 ξ/T
L luminosity, r distance
c speed of light
P ideal gas pressure
P = nkT
T temperature
In Ξ versus T plot means vertical section constant nT

30. Are the different ionization states in pressure equilibrium?
Ionization structure
Are the different ionization states in pressure equilibrium?

31. Continuous ionization distribution
Assume solar abundances
Continuous distribution over 3.5 orders in ξ
dNH/dlnξ~ξα
α=0.40±0.05

32. Spectral variability: low state
New observation
March
Low hard state
Preliminary results
M. Feňovčík

33. 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 Feňovčík, in prep.

34. Spectral variability: NGC 3783
RGS
EPIC pn
Higher ξ absorber is variable, while low ξ is not in NGC 3783 XMM data
(Behar et al. 2003, Reeves et al. 2004)

35. Geometry of the absorber

36. Geometry of the wind v (km/s) -166 -1040 ξ=1 0.0007 0.0001 ξ=1000 0.7
0.1

37. 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

38. 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

41. 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 ξ
The outflow occurs in narrow steamers
Likely, part of the outflow escapes