The XMM-<i>Newton</i>HBS28 sample: Studying the obscuration in hard X-ray selected AGNs

Caccianiga, A.; Severgnini, P.; Braito, V.; Ceca, R. Della; Maccacaro, T.; Wolter, A.; Barcons, X.; Carrera, Francisco J.; Lehmann, I.; Page, M. J.; Saxton, R. D.; Webb, N. A.

doi:10.1051/0004-6361:20034148

Cited by 86 publications

(139 citation statements)

References 62 publications

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“…We used two power-laws with the same photon index fixed to Γ = 1.9 (Reeves & Turner 2000;Caccianiga et al 2004;Page et al 2004) to model the scattered and the primary X-ray emission. While the scattering component was absorbed only through the Galactic column density, we estimated an intrinsic column density that absorbs the primary X-ray emission of N H = (4 ± 2) × 10 23 cm −2 (χ 2 /d.o.f.…”

Section: Xmm-newton Archival Datamentioning

confidence: 99%

Suzaku and SWIFT-BAT observations of a newly discovered Compton-thick AGN

Severgnini

Caccianiga

Ceca

et al. 2010

A&A

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Context. Obscured AGN are fundamental to understand the history of supermassive black hole growth and their influence on galaxy formation. However, the Compton-thick AGN (N H > 10 24 cm −2 ) population is basically unconstrained, with less than a few dozen confirmed Compton-thick AGN found and studied so far. A way to select heavily obscured AGN is to compare the X-ray emission below 10 keV (which is strongly depressed) with the emission from other bands that are less affected by the absorption, like the IR band. To this end, we have cross-correlated the 2XMM catalogue with the IRAS Point Source catalogue and, by using the X-ray to infrared flux ratio and X-ray colours, we selected a well defined sample of Compton-thick AGN candidates at z < 0.1. Aims. The aim of this work is to confirm the nature and to study one of these local Compton-thick AGN candidates, the nearby (z = 0.029) Seyfert 2 galaxy IRAS 04507+0358, by constraining the amount of intrinsic absorption (N H ) and thus the intrinsic luminosity. Methods. To this end we obtained deep (100 ks) Suzaku observations (AO4 call) and performed a joint fit with SWIFT-BAT data. We analysed XMM-Newton, Suzaku and SWIFT-BAT data and present here the results of this broad-band (0.4−100 keV) spectral analysis. Results. We found that the broad-band X-ray emission of IRAS 04507+0358 requires a large amount of absorption (higher than 10 24 cm −2 ) to be well reproduced, thus confirming the Compton-thick nature of this source. In particular, the most probable scenario is that of a mildly (N H ∼ 1.3−1.5 × 10 24 cm −2 , L(2−10 keV) ∼ 5−7 × 10 43 erg s −1 ) Compton-thick AGN.

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Section: Xmm-newton Archival Datamentioning

confidence: 99%

Suzaku and SWIFT-BAT observations of a newly discovered Compton-thick AGN

Severgnini

Caccianiga

Ceca

et al. 2010

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“…8 is probably the best place where to look for Compton Thin QSO2; as shown in (e.g. Caccianiga et al 2004) the very positive HR2 reflects the relatively large intrinsic photoelectric absorption present in many QSO2 and responsible for their preferential discovery in hard X-ray surveys 6 . 6 We caution however that the separation in HR2 properties between Compton Thin and Compton Thick QSO2 is probably clear only for sources with redshift as high as in our learning sample (z <∼ 0.8); at Finally, we show in Fig.…”

Section: Fig 8 Left Panelmentioning

confidence: 98%

“…X-ray selection looks instead for luminous (L X,2−10 keV > 10 44 erg/s) significantly obscured (column density N H > 10 22 cm −2 ) sources, which are best selected in the E > 2 keV hard X-ray band (e.g. Mainieri et al 2002;Caccianiga et al 2004;Perola et al 2004;Vignali et al 2006;Della Ceca et al 2008;Krumpe et al 2008). Within the Unified Model (Antonucci 1993), obscuration of the central X-ray-emitting and Broad Line-emitting regions by an intervening torus gives rise to those consistent properties across both bands.…”

Section: Searching For Qso2 Candidatesmentioning

confidence: 99%

Cross-correlation of the 2XMMi catalogue with Data Release 7 of the Sloan Digital Sky Survey

Pineau

Motch

Carrera

et al. 2011

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The Survey Science Centre of the XMM-Newton satellite released the first incremental version of the 2XMM catalogue in August 2008. Containing more than 220 000 X-ray sources, the 2XMMi was at that time the largest catalogue of X-ray sources ever published and thus constitutes an unprecedented resource for studying the high-energy properties of various classes of X-ray emitters such as AGN and stars. Thanks to the high throughput of the EPIC cameras on board XMM-Newton accurate positions, fluxes, and hardness ratios are available for a substantial fraction of the X-ray detections. The advent of the 7th release of the Sloan Digital Sky Survey offers the opportunity to cross-match two major surveys and extend the spectral energy distribution of many 2XMMi sources towards the optical bands. This implies building extensive homogeneous samples with a statistically controlled rate of spurious matches and completeness. We here present a cross-matching algorithm based on the classical likelihood ratio estimator. The method developed has the advantage of providing true probabilities of identifications without resorting to heavy Monte-Carlo simulations. Over 30,000 2XMMi sources have SDSS counterparts with individual probabilities of identification higher than 90%. At this threshold, the sample has only 2% spurious matches and contains 77% of all expected SDSS identifications. Using spectroscopic identifications from the SDSS DR7 catalogue supplemented by extraction from other catalogues, we build an identified sample from which the way the various classes of X-ray emitters gather in the multi dimensional parameter space can be analysed and later used to design a source classification scheme. We illustrate the interest of this clean source sample by investigating two scientific use cases. In the first example we show how these multi-wavelength data can be used to search for new QSO2s. Although no specific range of observed properties allows us to efficiently identify Compton Thick QSO2s, we show that the prospects are much better for Compton Thin AGN2 and discuss several possible multi-parameter selection strategies. In a second example, we confirm the hardening of the mean X-ray spectrum with increasing X-ray luminosity on a sample of over 500 X-ray active stars and reveal that on average X-ray active M stars display bluer g − r colour indexes than less active ones. Although this catalogue of 2XMM-SDSS sources cannot be used directly for statistical studies, it nevertheless represents an excellent starting point to select well defined samples of X-ray-emitting objects.

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“…We define EXO50 the sources with f x / f o > 50; these are a rare class of X-ray emitting objects, as typically AGN have f x / f o = 1-10 (see e.g. Caccianiga et al 2004, Della Ceca et al 2004, Civano et al 2012. For instance, in the XMM-Newton Bright Survey (XBS, Della Ceca et al 2004, Caccianiga et al 2008), a complete sample of bright ( f (0.5−4.5keV) 7 × 10 −14 erg cm −2 s −1 ) X-ray selected sources almost completely identified (spectroscopic identification level ∼ 98%), EXO50 objects represents only ∼ 0.5% of the source population.…”

Section: The Exo50 Samplementioning

confidence: 99%

“…1), population, namely those sources with f x / f o >50 (more than 15 times the average values of unobscured broad line AGN, e.g. Caccianiga et al 2004, Della Ceca et al 2004, Civano et al 2012 and with f x > 10 −13 erg cm −2 s −1 . In this way we should efficiently select the best candidates to be obscured QSOs; at the same time, the source brightness ensures that the optical spectroscopic identification can be achieved 1 for sources with reasonably good quality X-ray data (>few hundred counts) to carry out a reliable X-ray spectral analysis.…”

Section: Introductionmentioning

confidence: 99%

Exploring the active galactic nuclei population with extreme X-ray-to-optical flux ratios (fx/fo > 50)

Ceca

Carrera

Caccianiga

et al. 2015

Monthly Notices of the Royal Astronomical Society

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The cosmic history of the growth of supermassive black holes in galactic centers parallels that of star-formation in the Universe. However, an important fraction of this growth occurs inconspicuously in obscured objects, where ultraviolet/optical/near-infrared emission is heavily obscured by dust. Since the X-ray flux is less attenuated, a high X-ray-to-optical flux ratio ( f x / f o ) is expected to be an efficient tool to find out these obscured accreting sources. We explore here via optical spectroscopy, X-ray spectroscopy and infrared photometry the most extreme cases of this population (those with f x / f o > 50, EXO50 sources hereafter), using a well defined sample of 7 X-ray sources extracted from the 2XMM catalogue. Five EXO50 sources (∼ 70 percent of the sample) in the bright flux regime explored by our survey ( f (2−10keV) 1.5 × 10 −13 erg cm −2 s −1 ) are associated with obscured AGN (N H > 10 22 cm −2 ), spanning a redshift range between 0.75 and 1 and characterised by 2-10 keV intrinsic luminosities in the QSO regime (e.g. well in excess to 10 44 erg s −1 ). We did not find compelling evidence of Compton Thick AGN. Overall the EXO50 Type 2 QSOs do not seem to be different from standard X-ray selected Type 2 QSOs in terms of nuclear absorption; a very high AGN/host galaxy ratio seems to play a major role in explaining their extreme properties. Interestingly 3 out of 5 EXO50 Type 2 QSO objects can be classified as Extreme Dust Obscured Galaxies (EDOGs, f 24 µm / f R 2000), suggesting that a very high AGN/host ratios (along with the large amount of dust absorption) could be the natural explanation also for a part of the EDOG population. The remaining 2 EXO50 sources are classified as BL Lac objects, having rather extreme properties, and which are good candidates for TeV emission.

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The XMM-NewtonHBS28 sample: Studying the obscuration in hard X-ray selected AGNs

Cited by 86 publications

References 62 publications

Suzaku and SWIFT-BAT observations of a newly discovered Compton-thick AGN

Suzaku and SWIFT-BAT observations of a newly discovered Compton-thick AGN

Cross-correlation of the 2XMMi catalogue with Data Release 7 of the Sloan Digital Sky Survey

Exploring the active galactic nuclei population with extreme X-ray-to-optical flux ratios (fx/fo > 50)

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