THE FIFTH DATA RELEASE SLOAN DIGITAL SKY SURVEY/
                    <i>XMM-NEWTON</i>
                    QUASAR SURVEY

Young, M.; Elvis, M.; Risaliti, G.

doi:10.1088/0067-0049/183/1/17

Cited by 88 publications

(64 citation statements)

References 102 publications

(130 reference statements)

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“…Because the errors on the photon index are not symmetric, we used the average value for the individual errors in each case. We obtain a mean value of Γ = 2.05 ± 0.03 with an intrinsic dispersion of σ = 0.26 ± 0.02 for the BSS and Γ = 1.98 ± 0.08 with an intrinsic dispersion of σ = 0.29 ± 0.05 for the HBSS, in agreement with previous works (Mateos et al 2010;Young et al 2009;Dadina 2008;Mainieri et al 2007;Page et al 2006;Mateos et al 2005a,b). Errors were extracted from the 1σ confidence contours.…”

Section: Photon Indexsupporting

confidence: 92%

“…An anti-correlation between the photon index and the X-ray luminosity has been recently reported by Green et al (2009) and Young et al (2009), whereas Saez et al (2008) found a "positive" correlation. It has to be noted that Saez et al (2008) took into account type 1 and type 2 AGN at the same time, the latter being more numerous than the former, whereas we here only considered type 1 AGN.…”

Section: Discussionmentioning

confidence: 82%

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The X-ray spectral properties of the AGN population in theXMM-Newtonbright serendipitous survey

Corral

Ceca

Caccianiga

et al. 2011

A&A

130

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Context. X-ray surveys are a key instrument in the study of active galactic nuclei (AGN). Thanks to their penetrating ability, X-rays are able to map the innermost regions close to the central super massive black hole (SMBH) as well as to detect and characterize its emission up to high redshift. Aims. We present here a detailed X-ray spectral analysis of the AGN belonging to the XMM-Newton bright survey (XBS). The XBS is composed of two flux-limited samples selected in the complementary 0.5−4.5 and 4.5−7.5 keV energy bands and comprising more than 300 AGN up to redshift ∼2.4. Methods. We performed an X-ray analysis following two different approaches: by analyzing individually each AGN X-ray spectrum and by constructing average spectra for different AGN types. Results. From the individual analysis, we find that there seems to be an anti correlation between the spectral index and the sources' hard X-ray luminosity, such that the average photon index for the higher luminosity sources (>10 44 erg s −1 ) is significantly (>2σ) flatter than the average for the lower luminosity sources. We also find that the intrinsic column density distribution agrees with AGN unified schemes, although a number of exceptions are found (3% of the whole sample), which are much more common among optically classified type 2 AGN. We also find that the so-called "soft-excess", apart from the intrinsic absorption, constitutes the principal deviation from a power-law shape in AGN X-ray spectra and it clearly displays different characteristics, and likely a different origin, for unabsorbed and absorbed AGN. Regarding the shape of the average spectra, we find that it is best reproduced by a combination of an unabsorbed (absorbed) power law, a narrow Fe Kα emission line and a small (large) amount of reflection for unabsorbed (absorbed) sources. We do not significantly detect any relativistic contribution to the line emission and we compute an upper limit for its equivalent width (EW) of 230 eV at the 3σ confidence level. Finally, by dividing the type 1 AGN sample into high-and low-luminosity sources, we marginally detect a decrease in the narrow Fe Kα line EW and in the amount of reflection as the luminosity increases, the "so-called" Iwasawa-Taniguchi effect.

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Section: Photon Indexsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 82%

The X-ray spectral properties of the AGN population in theXMM-Newtonbright serendipitous survey

Corral

Ceca

Caccianiga

et al. 2011

A&A

130

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“…These values are in excellent agreement with recent measurements of the mean photon index and intrinsic dispersion for type-1 AGN found in the literature (e.g. Young et al 2009;Dadina 2008;Mainieri et al 2007;Page et al 2006;Mateos et al 2005a,b). We note that hard X-ray selected samples ( > ∼ 20 keV) from the INTEGRAL and Swift satellites report marginally flatter spectral slopes for bright type-1 AGN, Γ ∼ 1.7−1.8 (Molina et al 2009;Winter et al 2009;Panessa et al 2008).…”

Section: The Broad Band X-ray Continuumsupporting

confidence: 92%

“…Various studies of the X-ray photon index have produced different results. Some authors claim an anti-correlation between the spectral photon index Γ and the X-ray luminosity (Young et al 2009;Saez et al 2008;Page et al 2005) while other studies suggest the opposite correlation (Dai et al 2004) or no correlation at all (Winter et al 2009;Mateos et al 2005b;George et al 2000;Reeves & Turner 2000). Studies of the X-ray spectra of AGN have generally shown no clear dependence of the AGN X-ray properties on the redshift (Mateos et al 2005a), although some exceptions have been found (Kelly et al 2007).…”

Section: Introductionmentioning

confidence: 99%

The XMM-NewtonWide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

Mateos¹,

Carrera

Page

et al. 2010

A&A

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Aims. We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2−10 keV (rest-frame) luminosities from ∼10 42 −10 45 erg s −1 and are detected up to redshift ∼4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift. We discuss the implications for models of AGN emission. Methods. We fitted the observed 0.2−12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results. We constrained the mean spectral index of the broad band X-ray continuum to Γ = 1.96 ± 0.02 with intrinsic dispersion σ Γ = 0.27 +0.01 −0.02 . The continuum becomes harder at faint fluxes and at higher redshifts and hard (2−10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in > ∼ 3% of our objects, with rest-frame column densities ∼a few ×10 22 cm −2 . The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is ∼36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT ∼ 100 eV and σ kT ∼ 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled out on the basis of the temperatures detected and the lack of correlation of the soft excess temperature with the hard X-ray luminosity over more than 2 orders of magnitude in luminosity. Furthermore, the high luminosities of the soft excess rule out an origin in the host galaxy.

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“…These studies, based on Einstein observations, found a mean value of α ox in the range 1.3−1.45. Subsequently, many investigations have been performed (e.g., Yuan et al 1998;Vignali et al 2003;Strateva et al 2005;Steffen et al 2006, hereafter S06;Just et al 2007, hereafter J07; Kelly et al 2008;Green et al 2009;Young et al 2009) which were mainly based on AGN samples selected from the Sloan Digital Sky Survey (SDSS). Most of the previous studies on the relationship between α ox , luminosity and redshift A&A 512, A34 (2010) were based on large samples of optically selected type 1 AGN with a high fraction of X-ray detections.…”

Section: Introductionmentioning

confidence: 99%

The X-ray to optical-UV luminosity ratio of X-ray selected type 1 AGN in XMM-COSMOS

Lusso

Comastri

Vignali

et al. 2010

A&A

Self Cite

372

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We present a study of the X-ray to optical properties of a sample of 545 X-ray selected type 1 AGN, from the XMM-COSMOS survey, over a wide range of redshifts (0.04 < z < 4.25) and X-ray luminosities (40.6 ≤ Log L [2−10] keV ≤ 45.3). About 60% of them are spectroscopically identified type 1 AGN, while the others have a reliable photometric redshift and are classified as type 1 AGN on the basis of their multi-band Spectral Energy Distributions. We discuss the relationship between UV and X-ray luminosity, as parameterized by the α ox spectral slope, and its dependence on redshift and luminosity. We compare our findings with previous investigations of optically selected broad-line AGN (mostly from SDSS). A highly significant correlation between α ox and L 2500 Å is found, in agreement with previous investigations of optically selected samples. We calculate bolometric corrections, k bol , for the whole sample using hard X-ray luminosities (L [2−10] keV ), and the Eddington ratios for a subsample of 150 objects for which black hole mass estimates are available. We confirm the trend of increasing bolometric correction with increasing Eddington ratio as proposed in previous works. A tight correlation is found between α ox and k bol , which can be used to estimate accurate bolometric corrections using only optical and X-ray data. We find a significant correlation between α ox and Eddington ratio, in which the ratio between X-ray and optical flux decreases with increasing Eddington ratio.

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THE FIFTH DATA RELEASE SLOAN DIGITAL SKY SURVEY/ XMM-NEWTON QUASAR SURVEY

Cited by 88 publications

References 102 publications

The X-ray spectral properties of the AGN population in theXMM-Newtonbright serendipitous survey

The X-ray spectral properties of the AGN population in theXMM-Newtonbright serendipitous survey

The XMM-NewtonWide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

The X-ray to optical-UV luminosity ratio of X-ray selected type 1 AGN in XMM-COSMOS

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