11

A. Streblyanska, G. Hasinger,A. Streblyanska, G. Hasinger,

A.A. Finoguenov, X. Barcons, S. Finoguenov, X. Barcons, S. Mateos, Mateos,

A. C. FabianA. C. Fabian

A relativisticA relativisticFe line in the mean X-ray Fe line in the mean X-ray

spectra of type-1 and type-2spectra of type-1 and type-2

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XMM-Newton X-ray observatory: a powerful tool for X-ray spectroscopy of a large number of

sources.

The advantage of XMM-Newton compared to Chandra is its wide energy band and its unprecedented sensitivity in the hard band, which is well suited to study very faint intrinsically absorbed X-ray sources.The large Effective Area of XMM mirrors allows us to study fainter haloes and objects.

Deep X-ray surveys with Chandra and XMM-Newton

Deep Chandra and XMM-Newton surveys allowed to reach extremely low flux levels and to resolve ~90% of the X-ray background (XRB) to discrete sources (< 10 keV).

33

CDFS: XMM PN+MOS RA 3:32:28 and DEC -27:48:30 (J2000)

The exposure time for good quality observation added up to ~ 370 ksec (XMM) +

1Ms Chandra dataset (Giacconi et al. 2002)

Lockman Hole: XMM PN+MOS

RA 10:52:43 and DEC +57:28:48 (J2000)The remaining exposure times after cleaning are ~770-800 ksec (PN-MOS1-MOS2) (PV+AO-1+AO-2 phases).

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From optical identifications we know that the dominant population in both surveys is a mixture of obscured (type-2) and unobscured (type-1) AGNs, with a small fraction of groups/clusters of galaxies. The fraction of obscurated objects increase at lower flux.

Study of properties and number abundance of groups at high redshifts is one of the most sensitive tests on the cluster evolution and provides a basis for a comparison with future surveys aimed to find more massive clusters at similar redshifts.

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Stacking XMM rest frame Stacking XMM rest frame spectra in deep fieldspectra in deep field

The next step after investigating the individual spectra was to group the faint objects by source classification and combine their spectra in order to determine general spectral properties for each type of object.

Using the extensive optical identification of AGN population in combination with 770 ksec XMM-Newton survey of the Lockman Hole, we have derived the average X-ray spectral properties of sources spectroscopically identified with the VLT and Keck telescopes. With data from the EPIC-pn and MOS detectors, we used a sample of 104 sources with redshift identification and photon counts > 200.

66

An important ingredient to the background synthesis models is the average X-ray spectrum of AGN (local samples of Seyfert-1 and Seyfert-2 galaxies: slope of the AGN spectrum and absorbing column). A possibility to detect a feature in the cosmic spectrum arising from the Fe line has been first studied by Schwartz (1988), where narrow Fe lines were assumed. A diversity in line shapes have been recently reported, as relativistic iron lines have been discovered in some objects with ASCA (Tanaka et al. 1995) and confirmed with XMM-Newton (Wilms et al. 2001, Fabian et al. 2002). The most recent evidence is controversial. Only a small fraction of Seyfert galaxies seems to emit relativistic iron lines (Balestra et al. 2004) and the line shapes observed with XMM-Newton and Chandra are more complicated. Frequently a narrow component is observed in the Fe line and the analysis of the broad, relativistic component is often hampered by systematic uncertainties in modelling the continuum.

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AGN-2

AGN-1

Redshifts distribution of the sources in our sample.

53 type-1 AGN 41 type-2 AGN

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Spectral analysisSpectral analysis•Each individual spectrum was fit with a single power law model •Both the ratio of the data to the model as well as a reconstructed unfolded spectrum was saved

•An average spectrum was created with a bin width of 0.25 keV for energies lower than 8 keV and a bin width 2 keV above

•Each spectrum was shifted to the rest frame:●For the ratio we increase the energies by the factor of (1+z). ●For the unfolded spectra we used the same

energy band to renormalize the spectra to the same value for further averaging and increase the energies by the factor of (1+z).

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Type-1 and Type-2 AGN (ratio)Type-1 and Type-2 AGN (ratio) PN+MOS. ~800 ksec

53 objects

Type-1 AGN

41 objects

Type-2 AGN

1010

LH data: unfolded spectra.LH data: unfolded spectra.

Type-1 AGN

Type-2 AGN

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type-1 AGN type-2 AGN

The ratio from the stacked unfolded spectrum (power law model)

The resulting ratio plots from mean unfolded spectra obtained by using averaging methods. The unfolded spectra are fit with a power-law model in the ranges 0.2-3 and 8-20 keV.

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Type-1 AGN: Unfolded spectraType-1 AGN: Unfolded spectrawabs * wabs(po + linemodel)NH = 5.7 × 1019 cm-2 (fixed) Photon index = 1.74±0.2NH = 8±1 × 1020 cm-2

ModeModell

Energy, keV

EW, eVEW, eV β Rin (Rg) Rout (Rg) i (deg) χ2/DOF

laor 6.46.4** 560±10560±1000

33** 3.1±1.03.1±1.0 400400-120-120 30±1.30±1.88

0.73/67

diskline 6.46.4** 480±60480±60 22** 6.4±1.26.4±1.2 22±422±4 29±1.29±1.33

0.70/67

GaussiaGaussiann

5.9±0.5.9±0.22

420±30420±30 -- -- -- -- 1.35/68* fixed

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Type-2 AGN: Unfolded spectraType-2 AGN: Unfolded spectraNH = 5.7 × 1019 cm-2 (fixed)Photon index = 1.6±0.2NH = 5.2±0.9 × 1020 cm-2

ModeModell

Energy, keV

EW, eVEW, eV β Rin (Rg) Rout (Rg) i (deg) χ2/DOF

laor 6.46.4** 455±3455±355

33** 6.2±0.6.2±0.99

400400-100-100 30±1.30±1.88

0.66/63

diskline 6.46.4** 320±2320±255

22** 6.06.0+0.1+0.1 800±40800±4000

29±1.29±1.33

0.80/63

GaussiaGaussiann

6.34±0.06.34±0.033

280±2280±255

-- -- -- -- 0.83/64* fixed

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Unfolded spectraUnfolded spectraType-1 AGNType-1 AGN Type-2 AGNType-2 AGN

EW = 455±40 eV

EW = 560±100 eV

A Doppler-broadened line with FWHM ~150,000 km s-1 can only be produced in the inner region of a relativistic accretion flow by fluorescence (Fabian et al. 2002). The observed FWHM and EW is larger than the average value found in Seyfert 1 galaxies (~ 500 eV, e.g. Nandra et al. 1997), but similar to the FWHM of some of the brightest nearby active galaxies (f.e., to MCG-6-30-15 with z=0.007749).

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DiscussionDiscussionThe large EW as the result of a high

metallicity(?)One of the explanations for the large EWs can be given by a model including ionized disc reflection with lines and edges from different ionization stages of iron blurred together by relativistic effects (Fabian et al. 2002b).The value of the Fe abundance determines the relative importance of the line complex in respect to the comptonization bump, seen at energies exceeding 10 keV. Since the observed EW of the broad Fe line is high, while the amplitude of a possible reflection component observed above 10 keV is small, this model yields a high Fe abundance as an explanation of the observation. This model has been applied for several nearby objects and can account for all the observed spectral features, but yields a large iron overabundance of 3-7 × solar (Tanaka et al. 2004, Boller et al. 2003).

The blurred ionised reflection models (Ross & Fabian 1993) with an iron abundance of 3 × solar (as needed for MCG-6-30-15) in order to obtain a high EW.

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DiscussionDiscussionThis is a novel method of measuring Fe abundance in QSO at X-rays, which in addition to the determination of redshifts will allow future X-ray surveys to give insight in the chemical evolution of the host environment of QSO.

An additional reason why our large equivalent width may be connected with a large metallicity is that most of our objects are quite distant and rather luminous AGNs.

Shemmer et al. (2004)The metallicity is correlated with the accretion rate, which is in turn related to the luminosity.

distant and luminous AGN -> high metallicity -> the large equivalent widths

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ConclusionConclusion

We derive an average rest-frame spectrum of AGN type one and two. The most prominent feature in the averaged spectrum is a presence of the fluorescent Fe line.

The average rest-frame spectrum of the XRB sources shows a strong, relativistic iron line, possibly due to a high metallicity in the average population.

The strong red wing of the line feature indicates some component of spin in the average black hole.

A very broad line feature is expected in the average X-ray background spectra (Fabian et al. 2000, Gilli et al. 2001), which should be included in future population synthesis models for the X-ray background.

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ConclusionConclusionIn spite of the variety and complexity of Fe features at low z bright objects (both type-1 and type-2 Seyfert), the average line shape at higher redshift is consistent with a relativistic disk line for type-1 and type-2 AGN with some evidence of an additional narrow component for type-2 AGN.

These findings strongly reinforce the science case These findings strongly reinforce the science case of the XEUS/Constellation-X mission; with the very of the XEUS/Constellation-X mission; with the very large collecting area we can expect to measure the large collecting area we can expect to measure the relativistic Fe line parameters of individual objects relativistic Fe line parameters of individual objects out to very high redshifts (z ~ 10). out to very high redshifts (z ~ 10).

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ReferencesReferences

Fabian, A. C., Iwashawa, K., Reynolds, C.S., & Young, A.J. 2000, PASP, 112, 1145Fabian, A. C., Vaughan, S., Nandra, K., et al. 2002, MNRAS, 335, 1FFabian, A. C., Ballantyne, D. R.; Merloni, A., et al. 2002b, MNRAS, 331, 35FHasinger G. 2004, Nuclear Physics B (Proc. Suppl.) 132, 86Mainieri, V., Bergeron, J., Rosati, P., et al. 2002, A&A, 393, 425Mateos, S., Barcons, X., et al. 2005, A&A, (in preparation)Soltan, A. 1982, MNRAS, 200, 115Wilms, J., Christopher S., Begelman, M. C., et al. 2001, MNRAS, 328, 27Worsley, M., Fabian, A. C., Mateos, S., et al. 2004, MNRAS 352, L28Yu Q., Tremaine S. 2002, MNRAS 335, 965