Seyfert galaxies and BeppoSAX

Matt, Giorgio

doi:10.1016/s0920-5632(98)00264-3

Cited by 4 publications

(5 citation statements)

References 50 publications

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“…Whereas in other Sy1s the cut-off occurs at much higher values, with lower limits around 200-300 keV (c.f. Gondek et al 1996;Matt 1998). More recently, Zdziarski et al (2000) have measured the average OSSE spectra of Sy 1 and Sy 2.…”

Section: Discussionmentioning

confidence: 99%

“…As the luminosity increases the atoms in the disk become increasingly ionized. At high ioniza-tion states the iron line is emitted at higher energies and its flux may decrease (Nandra et al 1997b and references therein;Matt 1998;Ross et al 1999, hereafter RFY99). Ultimately, the optical depth for photo-electric absorption decreases to such an extent that the continuum flux <30 keV is mostly reflected from the ionized disk and no longer absorbed (Basko et al 1974;RFY99).…”

Section: Introductionmentioning

confidence: 99%

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BeppoSAX spectroscopy of MR 2251-178: A test for ionized reflection in radio quiet QSOs

Orr

Barr

Guainazzi³

et al. 2001

A&A

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Abstract. We present the 0.1-200 keV BeppoSAX spectrum of MR 2251-178 observed at two epochs in 1998 separated by 5 months. Both epochs show identical spectral shape and X-ray flux. Analysis of the combined spectra allow us to confirm the presence of the ionized Fe Kα line detected by ASCA and to test the presence of reflection from ionized material. The best self-consistent spectral fit is obtained when including a contribution from a mildly ionized reflector (ξ0.01−100 ∼ 1625 erg cm s −1 , i.e. U0.1−10 ∼ 0.14) with a reflection fraction Rion ∼ 0.11. An exponential cut-off to the direct power-law continuum is then required at E ∼ 100 keV. The low energy spectrum is absorbed by ionized matter with a column density NW = (8.121 cm −2 and an X-ray ionization parameter U0.1−10 = 0.06± 0.01. The warm absorber column is slightly lower than that measured with ASCA. This change could be caused by bulk motion. The BeppoSAX absorber ionization parameter globally agrees with the "U versus Flux" correlation found for MR 2251-178 with EXOSAT, Ginga and ASCA. This suggests that the absorber is in a state of instantaneous ionization equilibrium.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

BeppoSAX spectroscopy of MR 2251-178: A test for ionized reflection in radio quiet QSOs

Orr

Barr

Guainazzi³

et al. 2001

A&A

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“…X-ray emission above 20 keV is commonly observed in Seyfert galaxies (see e.g. Matt 1998). Among clusters, hard X-ray emission has been found so far only in Coma and A 2256 with good significance, and in A 2199 with marginal significance (FuscoFemiano et al 1999(FuscoFemiano et al , 2000Kaastra et al 1999) As stated in Sect.…”

Section: Mrc 0625-536mentioning

confidence: 99%

BeppoSAX observation of Hercules A and MRC 0625-536

Trussoni

Feretti

Massaglia

et al. 2001

A&A

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Abstract. We present BeppoSAX observations of the two FR I type radio galaxies Hercules A (3C 348) and MRC 0625-536 in the energy range 0.2-200 keV. Data analysis shows that the X-ray flux from Hercules A is consistent with a diffuse thermal plasma emitting at T ≈ 4-5 keV with a possible, but somewhat uncertain, contribution of a softer component at T ≈ 3 keV. The non thermal emission from the active nucleus must be significantly smaller than the thermal one, and no indication of relevant core obscuration by a surrounding torus was detected. The flux from MRC 0625-536 originates from an extended region and has been fitted to a thermal law with T ≈ 5.7 keV and with a column density consistent with the galactic absorption. A spatially resolved spectral analysis does not show a relevant variation of the temperature and of the metallicity across the diffuse emission zone. A non thermal spectral component, related to the nuclear activity, may be present in the innermost region with some possible amount of local obscuration, contributing < ∼ 10% to the total luminosity. Hard X-ray emission from MRC 0625-536 has been detected in the PDS (15-200 keV) that may be related either to its galactic core or to the intracluster region.

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“…The Compton thick regime has been much less sampled either due to the lack of complete spectral coverage and/or all‐sky surveys above 10 keV (for mildly Compton thick sources) or because the entire high energy spectrum is down scattered by Compton recoil and therefore depressed at all energies (heavily Compton thick sources). Until now, indirect arguments have been used to probe this regime: the intensity of the iron line at 6.4 keV (equivalent width typically of the order of 1 keV, Matt 1999), the signature of strong Compton reflection or the ratio of the observed X‐ray luminosity against an isotropic indicator of the source intensity, often the [O iii ] 5007 Å luminosity. However, sometimes iron line and Compton reflection diagnostics may lead to a wrong classification, caused by a temporary switching off of the primary continuum (Guainazzi, Matt & Perola 2005) and not by thick absorption.…”

Section: Introductionmentioning

confidence: 99%

The fraction of Compton-thick sources in anINTEGRALcomplete AGN sample

Malizia

Stephen

Bassani

et al. 2009

Monthly Notices of the Royal Astronomical Society

127

147

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We study the NH distribution in a complete sample of 88 active galactic nuclei (AGN) selected in the 20–40 keV band from INTEGRAL/Imager on Board the Integral Satellite (IBIS) observations. We find that the fraction of absorbed (NH≥ 1022 cm2) sources is 43 per cent while the Compton thick AGN comprise 7 per cent of the sample. While these estimates are fully compatible with previous soft gamma‐ray surveys, they would appear to be in contrast with results reported by Risaliti, Maiolino & Salvati using an optically selected sample. This apparent difference can be explained as being due to a selection bias caused by the reduction in high energy flux in Compton thick objects rendering them invisible at our sensitivity limit. Taking this into account, we estimate that the fraction of highly absorbed sources is actually in close agreement with the optically selected sample. Furthermore, we show that the measured fraction of absorbed sources in our sample decreases from 80 to ∼20–30 per cent as a function of redshift with all Compton thick AGN having z≤ 0.015. If we limit our analysis to this distance and compare only the type 2 objects in our sample with the Risaliti et al. objects below this redshift value, we find a perfect match to their NH distribution. We conclude that in the low‐redshift bin we are seeing almost the entire AGN population, from unabsorbed to at least mildly Compton thick objects, while in the total sample we lose the heavily absorbed ‘counterparts’ of distant and therefore dim sources with little or no absorption. Taking therefore this low z bin as the only one able to provide the ‘true’ distribution of absorption in types 1 and 2 AGN, we estimate the fraction of Compton thick objects to be ≥24 per cent.

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Seyfert galaxies and BeppoSAX

Abstract: The contributions that BeppoSAX is expected to give and, after one and a half year of operation, has already given, to our knowledge of both type 1 and type 2 Seyfert galaxies are outlined and reviewed.

Cited by 4 publications

References 50 publications

BeppoSAX spectroscopy of MR 2251-178: A test for ionized reflection in radio quiet QSOs

BeppoSAX spectroscopy of MR 2251-178: A test for ionized reflection in radio quiet QSOs

BeppoSAX observation of Hercules A and MRC 0625-536

The fraction of Compton-thick sources in anINTEGRALcomplete AGN sample

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