Radio quiet AGN

B. CzernyCopernicus Astronomical

Center Warsaw

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VHE: are radio quiet AGN of any interest?

• bad news: only a small fraction of energy emitted above 100 KeV

• good news: AGN are the best probes of GR – X-ray spectroscopy

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Outline• general introduction

• X-ray spectroscopy

• current developments

based on results obtained in collaboration with: S. Collin

R. Goosman, M. Mouchet, A.-M. Dumont, M. Dovciak, V. Karas, A. Rozanska, G. Ponti

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Radio quiet AGN: intro• Definition:

• Properties: L from 1047 erg/s down broad band spectra

15log GHz)/F(B))(F(R

1))(/)5(log( BFGHzFF

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Radio-quiet AGN:intro

Albert Einstein (1879-1955)

Karl Schwarzschild (1873-1916)

Roy Kerr (1934-)

John Michell (1724-1793)

What are they? Black holes

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Radio quiet AGN: intro• What are they?

Accreting black holes

M ~ 106 – 1010 MsM~ from tens of Ms/year down

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Type 1 and type 2 objects

• Type 1: viewed roughly face on not strongly obscured but warm absorber present• Type 2: viewed at high inclinations strongly obscured (so

called „dusty/molecular torus” – most probably a

type of wind)High energy processes better followed in type

1 objects

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Components:• Cold optically thick accretion disk

• Hot optically thin plasma: geometry under discussion

Paticles roughly in Keplerian motion if pressure gradient unimportant

General relativity effect: presence of the marginally stable orbit

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Emission of accretion disks

• Stationary cold Keplerian acccretion disk

)(3

)(3

rfr

MGMrF

)()( 4 rTrF eff)(

3)(

3rf

r

MGMrF

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Accretion disk spectra

• Tmax ~105 K

• Disk emission peaks in far UV

Composite spectrum of bright quasars from sample of Fransis et al. (1991) after Morris, disk black body fit and schematic representation of the composite of Zheng et al/Laor et al.

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AGN flow geometry

L/LEdd < 0.1

disk far from marginally stable orbit

L/LEdd ~0.1 – 1

disk approaches marginally stable orbit

L/LEdd > 1

disk puffs up

Plausible geometry:

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Hot plasma emission• Bremsstrahlung• Synchrotron• Compton scattering

They form broad band spectra, difficult to assign to any particular distance from the gravity center; problems with definite determination of geometry

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Cold plasma emission• Thermal emission T ~ 105 K• Reprocessing of incident hard X-rays - thermalization - Thomson/Compton scattering - emission of atomic lines

In AGN elements like C,N,O, Si, S,… and Fe are not fully ionized in the disk even close to the marginally stable orbit

The option of line emission gives the full advantage of X-ray spectroscopy

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Broad Kα iron line• The shape of iron line tests the

particle motion close to horizon

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First detecion of Kα line

Detection of broad line in MCG -6-15-30 in ASCA data (Tanaka et al.. 1995)

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New observations of K

Broad line in the same object (MCG-6-30-15) measured with XMM

(Fabian et al. 2002)

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Variability of the line profile

Detection Line profile in of variosu luminosity states in ASCA data (Iwasawa et al.. 1996) broad line in MCG -6-15-30 in ASCA data (Tanaka et al.. 1995)

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Variability of hard X-rays

Lightcurve of MCG -6-15-30 form XMM (Ponti et al.. 2004)

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Time-dependent process

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Single spot• Computations of the reflection

component require solution of radiative transfer

- continuum - hundreds of atomic lines

A few codes exists. Titan/Noar code of Collin, Dumont & Abrassart (2000) is the best for optically thick media.

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Local spectrum

• Result depends on the flare phase

Local X-ray spectrum of irradiated accretion disk (Collin et al. 2003)

State 2: unexpanded disk

State 3: disk expanded due to the X-ray heating

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Single spot

R. Goosmann, in preparation

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Spot motion, light propagation in curved space

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Mean and rms spectra

Model parameters: a = 0.95 , i =30 deg, M = 107 MsTfl = 2e5 (r/18)3/2 [s], Ffl ~ r-3 [s], uniform flare distributionWork in progress…

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Single flare observations

• Bright flare from MCG -6-15-30

Ponti et al.. 2004

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Iron line delay in a single flare

Ponti et al. 2004

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In which sense AGN are better than GBH ?• Typical current count rate 10 cts/s 10 000 cts/s• Typical Keplerian timescale at inner disk

orbit 103 s 10-3 s• so counts per single orbit 100 cts 10 cts• lower ionization level GBH better for evolutionary studies

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Spatial resolution of observationsTypowe osiągane zdolności rozdzielcze:

Typ Masa Odległość 1”[cm] 1”[RSchw]

GBH 10 10 kpc 1017 3x1011

Milky Way 2.6x106 10 kpc 1017 106

MBH 107 50 Mpc 5x1020 109

MBH 109 1 Gpc 1022 2x109

Specjalne techniki (VLBI, fotometria plamkowa) pozwalają osiągnąć wyniki lepsze o parę rzędów wielkości, ale to wciąż za mało. Obszar w bezpośredniej bliskości czarnej dziury można jednak badać pośrednio poprzez analizę widma promieniowania, także w zależności od czasu.

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Are central objects indeed black holes?

• So far everything is consistent with GR expectations although accuracy is not high

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If something looks like a black hole …

From www page of Peter King

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