The ionization structure of the wind in NGC 5548

Katrien SteenbruggeHarvard-Smithsonian Center for Astrophysics

In collaboration with Jelle KaastraN. Arav, M. Crenshaw, S. Kraemer, R. Edelson, C. de Vries, I. George,

D. Liedahl, R. van der Meer, F. Paerels, J. Turner, T. Yaqoob

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

Seyfert galaxies• 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 5548, Kaastra et al. 2002

NGC 1068, Kinkhabwala 2002

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

Geometry of the absorber Elvis, 2000, ApJ, 545, 63

No absorptionBAL

NAL

Similarities between modelsElvis, 2000, ApJ, 545, 63

Clouds in pressure equilibrium with a hot outflow

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

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

Ionization parameter

• ξ = L/nr2

• L luminosity• n gas density• r distance

from source

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

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

Absorption componentsOutflow 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

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 0.05But multiple ionization parameters per velocity component !

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

X-ray spectra

• Combine HETGS resolution with λ range LETGS

• Probe low to highly ionized absorber

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

Velocity structure

• Resolve the highest UV outflow v for 6 ions

• Same outflow velocity structure as the 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

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

Velocity structure

• If we measure 1 outflow v

• Higher ionized ions have higher outflow velocities

Ionization structure of velocity components

HST STIS

FUSE

Ionization structure of the absorber

Both models require clouds in pressure equilibrium.

Pressure equilibrium implies several separate components with a different ionization

parameter.

Ionization structure

• Iron is best indicator of ionization

• H abundance = 10

• Lower ionized iron ionization is uncertain

(Netzer et al. 2003)

Ionization structure

• RGS data• Fe only• Model with 3,4

and 5 ionization components

Pressure equilibriumΞ = 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

Ionization structure

Are the different ionization states in pressure equilibrium?

Continuous ionization distribution

• Assume solar abundances

• Continuous distribution over 3.5 orders in ξ

• dNH/dlnξ~ξα

• α=0.40±0.05

Spectral variability: low state

• New observation• March 15 2005• Low hard state• Preliminary

results • M. Feňovčík

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.

Spectral variability: NGC 3783

Higher ξ absorber is variable, while low ξ is not in NGC 3783 XMM data

(Behar et al. 2003, Reeves et al. 2004)

RGS EPIC pn

Geometry of the absorber

Geometry of the wind

2/ cLM acc

2/ nrL

accloss MM

vnrmM ploss2

2

)/(cmv

p

v (km/s) -166 -1040

ξ=1 0.0007 0.0001

ξ=1000 0.7 0.1

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

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/vr

2) · 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

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