A constant pressure model for the Warm Absorber in NGC 3783

transcript

Anabela C. Gonçalves1,3

S. Collin1, A.-M. Dumont1, A. Rozanska2, M. Mouchet1, L. Chevallier1, R. Goosmann1

1 Observatoire de Paris-Meudon (LUTH), France2 Copernicus Astronomical Center (CAMK), Poland3 Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL), Portugal

Outline

The Warm Absorber (WA) ■ Generic properties

The TITAN code (A.-M. Dumont & S. Collin , Paris Observatory)■ Main characteristics■ Application range and examples

NGC 3783■ The data ■ Previous studies on the WA ■ Preliminary results obtained with the TITAN code

Conclusions and future work

Workshop: some open questions

The Warm Absorber in AGN

WA general properties

■ WA seems to be located between the disk and the NLR

■ Outflow of material at a few hundreds kms-1, possible multiple velocity components

■ The mass outflow can be important

(exact location? geometry?)

■ Warm (T ~ 105-106 K) plasma surrounding the active nucleus

■ Photoionized by X-rays produced near the black hole

(how much?) Inspired by Fabian (1998)

rge et al.

(1995)

NGC 3783

After Chandra and XMM-Newton:

■ Space observatories with grating spectrometers allow for line-resolved spectroscopy

i et al. (2002)

Warm Absorber observations

The importance of high(er) spectral resolution

Before Chandra and XMM-Newton (1999):

■ First WA observation in MR 2251-178 by Einstein (Halpern 1984)

Photoionization codes must follow improvement in data quality!

■ ASCA observations show the presence of a WA in ~ 50% nearby Type 1 AGN: detection of absorption edges, no details

TITAN photoionization code

missing species!

■ Designed for optically thick media (Dumont et al. 2000, Collin et al. 2004)

■ Computes the gas structure in thermal and ionization equilibrium, both locally and globally

■ 102 ions and atoms: H, He, C, N, O, Ne, Mg, Si, S, F

■ Computes the transfer for ~1000 lines and the continuum

■ Modes: Constant Density, Gaseous Pressure or Total Pressure

■ Calculates multi-angle spectra (outward, reflected and transmitted)

■ Accounts for Compton heating/cooling (coupled with NOAR code)

105 < nH < 1014 cm-3

NH < 1026 cm-2

8000 < T < 107 K

10 < < 105

■ Parameters’ optimal range:

= L/nHR2

Multi-angle spectra■ “normal direction” + 5 cones

(7’, 18°, 40°, 60°, 77°, 87°)

■ computes the transmitted, reflected and outward flux

Computes the transfer of lines and continuum■ No escape probability approximation, but throughout calculations (ALI)

TITAN photoionization code

Line profile studies

■ Accounts for P Cyg-like profiles

● Chandra data

TITAN model

OVIII 18.97

TITAN application examplesGoosmann et al.

(Poster at “The X-ray Universe 2005”)

Tomorrow: don’t miss Loic’s talk on “The puzzle of the soft X-ray excess in AGN: absorption or reflection? ” !!!

Chevallier et al.

(Poster at “The X-ray Universe 2005”)

Warm Absorber in NGC 3783

NGC 3783

■ Seyfert 1.5 at z = 0.0097, V ~ 13.5 mag, also very bright in X-rays and UV

■ X-ray (Chandra, XMM) and UV spectra (HST, FUSE): variability studies, line identifications, UV absorption lines studies, …

■ High quality Chandra spectrum, 900 ks exposure (Kaspi et al. 2002)

Kaspi et al. (2002)

=> Stratification of the WA

■ >100 absorption lines detected, covering a wide range in ionization

Krongold et al. (2003)

Previous NGC 3783 studies

Chandra data (56ks, 900ks spectra) ■ Kaspi et al. (00, 01, 02), Krongold et al. (03), Netzer et al. (03), …

XMM-Newton data (40ks, 280 ks spectra)■ Blustin et al. (2002), Behar et al. (2003), …

Main Results (also discussed in previous talk) ■ 2-phase gas (cold Low-Ionization Phase and hot High-Ionization Phase)

■ absorbing and emitting plasma are manifestations of the same gas

■ 2 or more velocity systems identified in Chandra observations

■ 1 single velocity system in XMM observations (v ~ -600 – -800 km s -1)

■ velocity systems compatible with UV absorption components

■ Albeit extensively studied, WA usually modelled with multiple zones of constant density

Previous NGC 3783 studies

Netzer et al. (03) modelling

= L/nHR2

NH = 2.1022 cm-2 = 4265 erg cm s-1

NH = 1.1022 = 1071

NH = 8.1021 = 68

■ Simulates the WA stratification with 3 components at constant density:

Netzer et al. (2003)

Our approach: a single medium in Total Pressure equilibrium

■ Results in the natural stratification of the WA

■ Allows to explain the presence of lines from different ionization states

■ Using the photoionization code TITAN allows to calculate the temperature, density and ionization structures, plus the absorption and emission spectra

■ Temperature profile is the same for different densities

■ Radiation pressure is similar, and so is the absorption spectrum, but not the emission component

Pressure equilibrium studies

Comparison to A. Rozanska’s work

■ We use the same code (TITAN), in a more recent version

■ We use the same mode: Total Pressure equilibrium

■ We use a different incident spectrum (not a simple power law spectrum)■ Multi-angle capability available in

most recent versions of the code

■ We can use “real” normal incidence, instead of isotropic approximation

■ We can obtain the emission and absorption contribution separately

Warm Absorber in NGC 3783

The observations

■ Data taken from the Chandra archives

■ HETG spectra reduced with CIAO 3.2.1

■ Available multi-wavelength observations provide information on incident spectrum

The Model

■ Incident spectrum as in Kaspi et al. (2001): broken power-law continuum

■ We have built an optimized grid of 4x4 models

grid parameters: = 2000, 2500, 3000, 3500 erg cm s-1

NH = 3.1022, 4.1022, 5.1022, 6.1022 cm-2

other parameters: nH (at surface) = 105 cm-3, vturb = 150 kms-1

■ For all models, we have calculated the outward and reflection spectra in multiple directions, plus the ionization and temperature structures

Kaspi et al. (2001)

Constant density modelConstant Density vs. Total Pressure

Preliminary results

Temperature profiles

■ The WA stratification can be obtained through constant pressure modelsConstant total pressure model

Preliminary results

Ionization structures

■ The WA stratification can be obtained through constant pressure modelsConstant density model Constant total pressure model

Preliminary results

Other Pysical quantities

■ e.g. Temperature profile, densityConstant density model Constant total pressure model

Preliminary results

Warm Absorber size

■ The cloud size is ~ 1.7 x larger for Constant Density models

Preliminary results

Calculated spectra

■ Our grid can account for the observations

■ The best model (NH = 4.1022 , = 2500) reproduces well the continuum and lines

■ Absorption features blueshifted (~800 kms-1)

Si XIII

Mg XII

Si XIV

Si XIII

Si XIV

Conclusions and future workSome conclusions…

■ The TITAN code is well adapted to the study of the WA in AGN

■ The WA in NGC 3783 can be modelled under total pressure equilibrium

■ For this model, we estimated a WA size R ~ 2 1017 cm (0.25 ly or 0.07 pc) compared to a 1.7 x larger WA for a model calculated at constant density

■ For a WA located at R ~ 4 105 RG (bottom NLR) <=>

●●

Mout /MEdd ~ 1(0.72 – 0.79 pc and R/R ~ 0.1)

■ For a WA located at R ~ 4 104 RG (BLR) <=> ●●

Mout /MEdd ~ 0.1(0.07 – 0.15 pc and R/R ~ 1)

■ To be compared to other mass outflows (Blustin PhD Thesis ; Blustin et al. 05): ●●

Mout /Macc < 400, 25 and 6.4 (3 outflowing components) ; 4.3 (average)

■ And WA location: 0.17 pc – 1.8 pc or 2.9 pc (Blustin PhD Thesis; Blustin et al. 05)

R < 5.7 pc (from variability considerations, Krongold et al. 05)

R < 3.2 pc, 0.63 pc and 0.18 pc (3 components, Netzer et al. 03)

If fcov ~1 => diffuse outward spectra

If fcov <1 => additional reflection spectra If Pcyg-like profiles =>

absorption profile (blueshifted)

outward emission (narrower)

emission from reflection (no shift or redshifted)

Conclusions and future work

Work in progress on the NGC 3673 Warm Absorber

■ Complete the grid with models using different vturb and nH

■ Study the line-emission components to better constrain the covering factor

Future work■ To use TITAN to model the WA observed in other Type 1 and Type 2 AGN

■ Lines missing in the model => complete the TITAN atomic data

■ A larger grid of models aimed at the future use of the code by the community

Workshop: open questions

How to produce redshifted (or more blueshifted) emission?■ Through balance of different components, line-of-sight projections, and adequate covering factor implying a reflected component

■ Can a “failed wind” explain larger absorption, less blueshifted, and/or redshifted emission?

What kind of geometry does such a model suggest?■ R/R smaller for higher mass output rate, but always within “reasonable” values

■ We can have full covering factor of the source in the line-of-sight and still contribution from the reflection on the neighbouring clouds

■ Cloud size => clumpiness? Preferred geometry?

A constant pressure model for the Warm Absorber in NGC 3783

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