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Approximately 3-17 per cent of active galactic nuclei (AGNs) without detected rest-frame UV/optical broad emission lines (type-2 AGN) do not show absorption in X-rays. The physical origin behind the apparently discordant optical/X-ray properties is not fully understood. Our study aims at providing insight into this issue by conducting a detailed analysis of the nuclear dust extinction and X-ray absorption properties of two AGNs with low X-ray absorption and with high optical extinction, for which a rich set of high-quality spectroscopic data is available from XMM-Newton archive data in X-rays and XSHOOTER proprietary data at UV-to-NIR wavelengths. In order to unveil the apparent mismatch, we have determined the AV/NH and both the supermassive black hole and the host galaxy masses. We find that the mismatch is caused in one case by an abnormally high dust-to-gas ratio that makes the UV/optical emission to appear more obscured than in the X-rays. For the other object, we find that the dust-to-gas ratio is similar to the Galactic one but the AGN is hosted by a very massive galaxy so that the broad emission lines and the nuclear continuum are swamped by the star light and difficult to detect., IO-P and FJC acknowledge financial support through grant AYA2015-64346-C2-1-P (MINECO/FEDER). SM acknowledges financial support by the Spanish Ministry of Economy and Competitiveness through grant AYA2016-76730-P (MINECO/FEDER). AC, RD, PS and VB acknowledge financial support by the Italian Space Agency (contract ASI-INAF I/037/12/0). Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society and the Higher Education Funding Council for England. The SDSS web site is http://www.sdss.org/. The STARLIGHT project is supported by the Brazilian agencies CNPq, CAPES and FAPESP and by the France-Brazil CAPES/Cofecub program.

Herder, Jan-Willem den et al., ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z = 10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z-0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs. The ORIGIN mission includes a Transient Event Detector (coded mask with a sensitivity of 0.4 photon/cm2/s in 10 s in the 5–150 keV band) to identify and localize 2000 GRBs over a five year mission, of which -65 GRBs have a redshift > 7. The Cryogenic Imaging Spectrometer, with a spectral resolution of 2.5 eV, a field of view of 30 arcmin and large effective area below 1 keV has the sensitivity to study clusters up to a significant fraction of the virial radius and to map the denser parts of the WHIM (factor 30 higher than achievable with current instruments). The payload is complemented by a Burst InfraRed Telescope to enable onboard red-shift determination of GRBs (hence securing proper follow up of high-z bursts) and also probes the mildly ionized state of the gas. Fast repointing is achieved by a dedicated ControlledMomentum Gyro and a low background is achieved by the selected low Earth orbit., The team likes to express its appreciation for the support of Astrium UK for the present study.

We have determined the relation between the AGN luminosities at rest-frame 6 ��m associated to the dusty torus emission and at 2-10 keV energies using a complete, X-ray flux limited sample of 232 AGN drawn from the Bright Ultra-hard XMM-Newton Survey. The objects have intrinsic X-ray luminosities between 10^42 and 10^46 erg/s and redshifts from 0.05 to 2.8. The rest-frame 6 ��m luminosities were computed using data from the Wide-Field Infrared Survey Explorer and are based on a spectral energy distribution decomposition into AGN and galaxy emission. The best-fit relationship for the full sample is consistent with being linear, L_6 ��m $\propto$ L_2-10 keV^0.99$\pm$0.032, with intrinsic scatter, ~0.35 dex in log L_6 ��m. The L_6 ��m/L_2-10 keV luminosity ratio is largely independent on the line-of-sight X-ray absorption. Assuming a constant X-ray bolometric correction, the fraction of AGN bolometric luminosity reprocessed in the mid-IR decreases weakly, if at all, with the AGN luminosity, a finding at odds with simple receding torus models. Type 2 AGN have redder mid-IR continua at rest-frame wavelengths, Accepted for publication in MNRAS. 24 pages, 10 figures and 5 tables. This version includes minor changes to the text and Table 2 in response to comments from the referee

Hawkins reported on a class of 'naked' active galactic nuclei (AGN) characterized by strong amplitude optical brightness variability and the complete absence of broad emission lines in the optical spectrum. The variability suggests that the nucleus is seen directly, however the absence of broad lines contradicts the simple formulation of Unified Models for AGN. We present the results of quasi-simultaneous spectroscopic observations with XMM-Newton and New Technology Telescope (NTT) (La Silla) of two 'naked' AGN. We confirm the 'naked' nature of Q2131-427 for which no broad emission line components have been detected in the optical spectrum and its X-ray spectrum shows no signs of intrinsic absorption. The optical and X-ray mismatch in this source cannot be ascribed to a high nuclear dust-to-gas ratio and a Compton-thick nature is ruled out on the basis of the high F(X)/F([OIII]) ratio. The broad-line region (BLR) may be completely absent in this source, possibly as a consequence of its low Eddington ratio. On the other hand, the optical spectrum of Q2130-431 shows H alpha and H beta broad emission line components, revealing the presence of a BLR. A mild X-ray absorption is expected in intermediate type 1.8 Seyfert galaxies like Q2130-431, however we put a very low upper limit on the column density (

The X-ray spectra of active galactic nuclei (AGN) unveil properties of matter around the super massive black hole (SMBH). We investigate the X-ray spectra of AGN focusing on Compton reflection and fluorescence, important processes of interaction between primary radiation and circum-nuclear material. Unresolved emission lines (most notably the Fe line) in the X-ray spectra of AGN indicate that this material is located far away from the SMBH. Contributions from the inner accretion disk, affected by relativistic effects, have also been detected in several cases. We studied the average X-ray spectrum of a sample of 263 X-ray unabsorbed AGN that yield 419023 counts in the 2-12 keV rest-frame band distributed among 388 XMM-Newton spectra. We fitted the average spectrum using a (basically) unabsorbed power law (primary radiation). From second model that represents the interaction of the primary radiation with matter located far away from the SMBH, we found that it was very significantly detected. Finally, we added a contribution from interaction with neutral material in the accretion disk close to the central SMBH, which is therefore smeared by relativistic effects, which improved the fit at 6 sigma. The reflection factors are 0.65 for the accretion disk and 0.25 for the torus. Replacing the neutral disk-reflection with low-ionisation disk reflection, also relativistically smeared, fits the data equally well, suggesting that we do not find evidence for a significant ionisation of the accretion disk. We detect distant neutral reflection in the average spectrum of unabsorbed AGN with z=0.8. Adding the disk-reflection component associated with a relativistic Fe line improves the data description at 6 sigma confidence level, suggesting that both reflection components are present. The disk-reflection component accounts for about 70 % of the total reflected flux., Comment: Accepted by A&A. 10 pages, 7 figures

We present the results of a correlation between the nuclear 2-10 keV and radio luminosities for a well defined sample of local Seyfert galaxies.

The Chandra Deep Field is the region of the sky with the highest concentration of X-ray data available: 4Ms of Chandra and 3Ms of XMM data, allowing excellent quality spectra to be extracted even for faint sources. We take advantage of this in order to compile a sample of heavily obscured Active Galactic Nuclei (AGN) using X-ray spectroscopy. We select our sample among the 176 brightest XMM sources, searching for either a) flat X-ray spectra (Photon index, To appear in A&A. 14 pages

International audience; The Chandra Deep Field is the region of the sky with the highest concentration of X-ray data available: 4 Ms of Chandra and 3 Ms of XMM-Newton data, allowing excellent quality spectra to be extracted even for faint sources. We took advantage of this to compile a sample of heavily obscured active galactic nuclei (AGN) using X-ray spectroscopy. We selected our sample among the 176 brightest XMM-Newton sources, searching for either flat X-ray spectra (Γ

One of the main themes in extragalactic astronomy for the next decade will be the evolution of galaxies over cosmic time. Many future observatories, including JWST, ALMA, GMT, TMT and E-ELT will intensively observe starlight over a broad redshift range, out to the dawn of the modern Universe when the first galaxies formed. It has, however, become clear that the properties and evolution of galaxies are intimately linked to the growth of their central black holes. Understanding the formation of galaxies, and their subsequent evolution, will therefore be incomplete without similarly intensive observations of the accretion light from supermassive black holes (SMBH) in galactic nuclei. To make further progress, we need to chart the formation of typical SMBH at z>6, and their subsequent growth over cosmic time, which is most effectively achieved with X-ray observations. Recent technological developments in X-ray optics and instrumentation now bring this within our grasp, enabling capabilities fully matched to those expected from flagship observatories at longer wavelengths., 8 pages, Science White paper submitted to Astro2010 Decadal survey. Supplementary information available at http://astro.imperial.ac.uk/research/ixo/smbh_growth.shtml

One of the most important parameters in the XRB (X-ray background) synthesis models is the average efficiency of accretion onto SMBH (super-massive black holes). This can be inferred from the shape of broad relativistic Fe lines seen in X-ray spectra of AGN (active galactic nuclei). Several studies have tried to measure the mean Fe emission properties of AGN at different depths with very different results. We compute the mean Fe emission from a large and representative sample of AGN X-ray spectra up to redshift ~ 3.5. We developed a method of computing the rest-frame X-ray average spectrum and applied it to a large sample (more than 600 objects) of type 1 AGN from two complementary medium sensitivity surveys based on XMM-Newton data, the AXIS and XWAS samples. This method makes use of medium-to-low quality spectra without needing to fit complex models to the individual spectra but with computing a mean spectrum for the whole sample. Extensive quality tests were performed by comparing real to simulated data, and a significance for the detection of any feature over an underlying continuum was derived. We detect with a 99.9% significance an unresolved Fe K-alpha emission line around 6.4 keV with an EW ~ 90 eV, but we find no compelling evidence of any significant broad relativistic emission line in the final average spectrum. Deviations from a power law around the narrow line are best represented by a reflection component arising from cold or low-ionization material. We estimate an upper limit for the EW of any relativistic line of 400 eV at a 3 sigma confidence level. We also marginally detect the so-called Iwasawa-Taniguchi effect on the EW for the unresolved emission line, which appears weaker for higher luminosity AGN., Comment: Accepted for publication in A&A. 12 pages, 12 figures

10 pages.-- Contribution to the 39th ESLAB symposium, ESA-SP (in press)., In this paper I review the main topics on the energetic Universe that have been put forward as main science goals in the Cosmic Vision 2015-2025 exercise. I discuss the study of matter under extreme conditions (both under strong gravity and at ultra-high densities), the cosmology of baryons (assembly of ordinary matter in dark-matter dominated structures and the creation of heavy elements) and the co-eval growth of super-massive black holes and stars in galaxies along cosmic history. Most of these topics can be addressed with a large-aperture deep Universe X-ray space observatory that can be flown soon after 2015, complemented by gravitational wave observatories (LISA), a focussing gamma-ray observatory, a far infrared high-sensitivity observatory and an X-ray survey telescope., Financial support was provided by the Spanish Ministerio de Educación y Ciencia, under project ESP2003-00812.

We have performed a detailed analysis of 3 optically normal galaxies extracted from the XMM Bright Serendipitous Source Sample. Thanks to the good statistics of the XMM-Newton data, we have unveiled the presence of an AGN in all of them. In particular, we detect both X-ray obscured (N_H>10^{22} cm^{-2}) and unobscured (N_H, Comment: Accepted for publication on A&A; 11 pages, 8 figures

We study the XMM-Newton spectra of a sample of 32 soft X-ray selected QSOs. Our goal is to check, using the spectra of moderate redshift (z ∼ 1.5), faint (f0.2-8 keV > 5 × 10-15 erg cm-2 s-1) broad-line QSOs, previous claims for either significant intrinsic absorption or spectral hardening at high energies. We derive hardness ratios for all sources and furthermore we perform spectral fits for the 11 brighter sources. The majority of sources have steep spectra Γ > 1.9. We find a few QSOs with large amounts of intrinsic absorption, as high as NH ∼ 1023 cm-2. We find no strong evidence for spectral hardening above 2 keV. The coadded QSO spectrum is well described by a single power-law with photon index of ∼1.9, demonstrating that, on average, any effects of absorption are not important. This suggests that the discrepancy between the X-ray background and the (soft X-ray selected) QSO spectrum holds well at the faint fluxes probed here.

The launch of the Chandra (NASA) and XMM-Newton (ESA) X-ray observatories in 1999 has revolutionized our view of the Universe, by providing astrophysical information about many classes of sources with unprecedent detail. The high throughput of XMM-Newton makes it the ideal instrument to provide low to moderate resolution spectroscopy of faint and extended sources. After 3 years of operations, XMM-Newton has observed many types of astronomical sources and delivered very interesting results in many areas. In this review, we highlight a few points where the contribution of XMM-Newton has significantly furthered our knowledge of the energetic Universe., Comment: 21 pages, inivited paper to appear in the "Boletin de la SEA", July 2003 issue (electronic release at http://sea.am.ub.es)

The XMM-Newton Survey Science Center is currently conducting an optical identification programme of serendipitous EPIC sources at low galactic latitudes. The aim of this study is to quantify the various populations contributing to the overall X-ray emission of the Galaxy and elaborate identification rules that can be later applied to the bulk of the low galactic latitude EPIC detections. We report here on preliminary results from an optical campaign performed in two very low b XMM-Newton fields and discuss the contributions of the various X-ray populations. This paper is presented on behalf of the Survey Science Center and of the AXIS collaboration., 4 pages 3 figures. To appear in the Proceedings of the Symposium on `New Visions of the X-ray Universe in the XMM-Newton and Chandra Era', 26-30 November 2001, ESTEC, The Netherlands

The XMM-Newton Survey Science Center is constructing a large (~1000 sources) and complete sample of bright serendipitous XMM-Newton sources at high galactic latitude, so as to allow both the discovery of sources of high individual interest as well as statistical population studies. The sample, known as ``The XMM-Newton Bright Serendipitous Source Sample" (XMM-Newton BSS), has a flux limit of ~10^(-13) cgs in the 0.5--4.5 keV energy band and will be fundamental in complementing other medium and deep survey programs (having fluxes 10 to 100 times fainter) in order to: a) characterize the X-ray sky and its constituents, b) understand the evolution of the population selected and c) define statistical identification procedures to select rare and interesting populations of X-ray sources (e.g. high z clusters of galaxies, BL Lacs, type 2 QSOs, etc..). We discuss here the scientific rationale and the details of the project and we present some preliminary results., Comment: 8 pages, 5 figures, Latex manuscript, Proc. Symnposium ``New Visions of the X-ray Universe in the XMM-Newton and Chandra Era", 26-30 November 2001, ESTEC, The Netherlands

We report on the first deep X-ray survey with the XMM-Newton observatory during the performance verification phase. The field of the Lockman Hole, one of the best studied sky areas over a very wide range of wavelengths, has been observed. A total of ~ 100 ksec good exposure time has been accumulated. Combining the images of the European Photon Imaging Camera (EPIC) detectors we reach a flux limit of 0.31, 1.4 and 2.4 ; 10-15 erg cm-2 s-1, respectively in the 0.5-2, 2-10, and 5-10 keV band. Within an off-axis angle of 10 arcmin we detect 148, 112 and 61 sources, respectively. The log(N)-log(S) relation in the three bands is compared with previous results. In particular in the 5-10 keV band these observations present the deepest X-ray survey ever, about a factor 20 more sensitive than the previous BeppoSAX observations. Using X-ray spectral diagnostics and the set of previously known, spectroscopically identified ROSAT sources in the field, the new sources can be classified. XMM-Newton detects a significant number ( ~ 40%) of X-ray sources with hard, probably intrinsically absorbed X-ray spectra, confirming a prediction of the population synthesis models for the X-ray background. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).

We have discovered an obscured active galaxy at redshift z = 1.246 identified with the ROSAT X-ray source RX J1011.2+5545. We report on multiwavelength observations of this source and discuss its X-ray, optical and radio properties. This is the first X-ray selected, obscured active galaxy at high redshift to be shown to be radio-loud, with a radio counterpart exhibiting a classical double-lobe morphology., 5 pages, 6 ps figures included, uses mn.sty. Accepted for publication in MNRAS

We present results of an ongoing program to study the gaseous extent of galaxies and the origin of QSO absorption line systems. For \lya absorption systems, we find that absorption equivalent width depends strongly on galaxy impact parameter and galaxy $B$-band luminosity, and that the gaseous extent of individual galaxies scales with galaxy $B$-band luminosity as $r\propto L_B^{0.40\pm0.09}$. Applying the results to galaxies in the Hubble Deep Field to calculate the predicted number density of \lya absorption lines as a function of redshift and comparing it with observations, we find that at least 50% and perhaps as much as 100% of \lya absorption systems with $W\apg0.32$ \AA can be explained by the extended gaseous envelops of normal galaxies. The anti-correlation analysis has also been performed on \civ absorption line systems, and the results show that the ionized gas cross section scales with galaxy $B$-band luminosity as $r\propto L_B^{0.76\pm0.26}$., Comment: 4 pages, LATEX, with 3 eps figures, blois.sty. To appear in the Proceedings of Xth Rencontres de Blois (June 28 - July 4, 1998) on The Birth of Galaxies

We review recent discoveries of obscured Active Galactic Nuclei at significant redshifts with X-ray observations. Most, if not all, the X-ray luminous galaxies found at faint X-ray fluxes could in fact be obscured AGN, where the obscuring material is also forming stars copiously. Given that AGN of various types appear to dominate the source populations at all X-ray fluxes, we also discuss their clustering properties. Current results imply that the population of X-ray selected AGN is not strongly biased, and therefore X-ray observations can be used to trace the distribution of matter out to redshifts ∼ 2., Partial financial support for this work was provided by the DGESID under project PB95-0122. ACF thanks the Royal Society for support.

We present initial results of a program to obtain and analyze HST WFPC2 images of galaxies in fields of HST spectroscopic target QSOs. The goal of the program is to investigate how the properties of \lya absorption systems observed in the spectra of background QSOs vary with the properties of intervening galaxies. We found that \lya absorption equivalent width depends strongly on galaxy impact parameter and galaxy B-band luminosity, and that the gaseous extent of individual galaxies scales with galaxy B-band luminosity by $r\propto L_B^{0.35\pm0.10}$., Comment: 2 pages, LATEX, with 1 ps figure, conf_iap.sty. To appear in the Proceedings of 13th IAP Colloquium (July 1-5, 1997) Structure and Evolution of the Intergalactic Medium from QSO Absorption Line Systems, ed. P. Petitjean, S. Charlot

We present initial results of a program to obtain and analyze HST WFPC2 images of galaxies identified in an imaging and spectroscopic survey of faint galaxies in fields of HST spectroscopic target QSOs. We measure properties of 87 galaxies, of which 33 are associated with corresponding \lya absorption systems and 24 do not produce corresponding \lya absorption lines to within sensitive upper limits. Considering only galaxy and absorber pairs that are likely to be physically associated and excluding galaxy and absorber pairs within 3000 \kms of the background QSOs leaves 26 galaxy and absorber pairs and seven galaxies that do not produce corresponding \lya absorption lines to within sensitive upper limits. Redshifts of the galaxy and absorber pairs range from 0.0750 to 0.8912 with a median of 0.3718, and impact parameter separations of the galaxy and absorber pairs range from 12.4 to $157.4 h^{-1}$ kpc with a median of $62.4 h^{-1}$ kpc. The primary result of the analysis is that the amount of gas encountered along the line of sight depends on the galaxy impact parameter and B-band luminosity but does not depend strongly on the galaxy average surface brightness, disk-to-bulge ratio, or redshift. This result confirms and improves upon the anti-correlation between \lya absorption equivalent width and galaxy impact parameter found previously by Lanzetta et al. (1995). There is no evidence that galaxy interactions play an important role in distributing tenuous gas around galaxies in most cases. Galaxies might account for all \lya absorption systems with $W > 0.3$ ��, but this depends on the unknown luminosity function and gaseous cross sections of low-luminosity galaxies as well as on the uncertainties of the observed number density of \lya absorption systems., Minor changes. Figure 1 stays intact and is available at ftp://ftp.ess.sunysb.edu/pub/lanzetta/wfpc/

We present initial results of a program to obtain and analyze HST WFPC2 images of galaxies in fields of HST spectroscopic target QSOs. The goal of the program is to investigate how the properties of \lya absorption systems observed in the spectra of background QSOs vary with the properties of intervening galaxies. We found that \lya absorption equivalent width depends strongly on galaxy impact parameter and galaxy B-band luminosity, and that the gaseous extent of individual galaxies scales with galaxy B-band luminosity by $r\propto L_B^{0.35\pm0.10}$., 2 pages, LATEX, with 1 ps figure, conf_iap.sty. To appear in the Proceedings of 13th IAP Colloquium (July 1-5, 1997) Structure and Evolution of the Intergalactic Medium from QSO Absorption Line Systems, ed. P. Petitjean, S. Charlot

A sample of 198 soft X--ray selected active galactic nuclei (AGN) from the ROSAT International X--ray Optical Survey (RIXOS), is used to investigate the X--ray luminosity function and its evolution. RIXOS, with a flux limit of 3E-14 erg s-1 cm-2 (0.5 to 2.0 keV), samples a broad range in redshift over 20 deg^2 of sky, and is almost completely identified; it is used in combination with the Einstein Extended Medium Sensitivity Survey (EMSS), to give a total sample of over 600 AGN. We find the evolution of AGN with redshift to be consistent with pure luminosity evolution (PLE) models in which the rate of evolution slows markedly or stops at high redshifts z>1.8. We find that this result is not affected by the inclusion, or exclusion, of narrow emission line galaxies at low redshift in the RIXOS and EMSS samples, and is insensitive to uncertainties in the conversion between flux values measured with ROSAT and Einstein. We confirm, using a model independent Ve/Va test, that our survey is consistent with no evolution at high redshifts., 10 pages, LaTeX file, PS figures and mn.sty. Accepted in MNRAS

We analyze the $2-10$~keV X-ray emission of complete samples of AGN and galaxies selected at 12$\mu$m and recently compiled by Rush, Malkan \& Spinoglio (1993). As a necessary complement we also study the IR emissivity of the largest sample of hard X--ray selected AGN (Grossan 1992). Our purposes are to probe the unified scheme of active nuclei and to evaluate the local X--ray volume emissivity of low luminosity and `hidden' AGN. We confirm that X-ray emission is basically restricted to AGN, Seyfert 1's being much more powerful emitters than Seyfert 2's. We find no signal of X-ray emission for the remaining galaxies selected at $12\mu$m, not even for those having a flat far-infrared spectrum, which would be prime candidates to host hidden AGN. Our result on the local volume emissivity of the Seyfert 1's is fully consistent with those derived from studies of the hard X--ray luminosity function. However the 95$\%$ upper limits to the local emissivity we derive for the Seyfert 2 class and for the most likely `hidden' AGN candidates, severely constrain (and in some cases exclude) models of the X--ray background based on the unified Seyfert scheme. We also find that less than $\sim20$\% of Seyfert 1-like AGN and less than $\sim 50$\% of Seyfert 2-like AGN can be `hidden' in the non-Seyfert galaxy samples assuming that the X-ray to 12$\mu$m flux ratios measured in the 12$\mu$m selected samples can be considered typical for these classes of objects. In this case, the number ratio of Seyfert 2 to Seyfert 1 galaxies ranges from 1 to 2., Comment: Text: 31 pages (tex) + 3 tables (tex) + 6 figures (ps); uuencoded

Observations in the last decade have provided strong evidence that the growth of supermassive black holes at the centres of galaxies is among the most influential processes in galaxy evolution. Open questions that relate to our current understanding of black hole growth and its relation to the build-up of galaxies at redshifts z=1-4, when most black holes and stars we see in present-day galaxies were put in place, include: what is the nature of AGN feedback and whether it plays a significant role in the evolution of galaxies? what is the dominant population of accreting AGN at that critical epoch? is it dominated by obscured objects as required by many current observations and models? The Athena+ mission concept will provide the technological leap required for a breakthrough in our understanding of AGN and galaxy evolution at the heyday of the Universe. The high throughput of Athena+ will allow the systematic study of the incidence, nature and energetics of AGN feedback processes to z~4 via the identification and measurement of blue-shifted X-ray absorption lines. The excellent survey and spectral capabilities of the Athena+ Wide Field Imager will complete the census of black hole growth by yielding samples of up to 100 times larger than is currently possible of the most heavily obscured, including Compton thick, AGN to redshifts z~4. The demographics of this population relative to their hosts is fundamental for understanding how major black hole growth events relate to the build-up of galaxies., Supporting paper for the science theme "The Hot and Energetic Universe" to be implemented by the Athena+ X-ray observatory (http://www.the-athena-x-ray-observatory.eu). 7 pages, 3 figures

[Context]: X-ray spectroscopy of active galactic nuclei (AGN) offers the opportunity to directly probe the inner regions of the accretion disk. Reflection of the primary continuum on the circumnuclear accreting matter produces features in the X-ray spectrum that help to explore the physics and the geometry of the innermost region, close to the central black hole. [Aims]: We present the results of our analysis of average AGN XMM-Newton X-ray spectra in the Chandra Deep Field South observation (hereafter, XMM CDFS), in order to explore the Fe line features in distant AGN up to z ~ 3.5. [Methods]: We computed the average X-ray spectrum of a sample of 54 AGN with spectroscopic redshifts and signal-to-noise ratio in the 2-12 keV rest-frame band larger than 15 in at least one EPIC camera (for a total of 100 X-ray spectra and 181 623 net counts in the 2-12 keV rest-frame band). We have taken the effects of combining spectra from sources at different redshifts and from both EPIC-pn and EPIC-MOS cameras into account, as well as their spectral resolution; we checked our results using thorough simulations. We explored the iron line components of distant AGN focusing on the narrow core which arises from material far from the central BH and on the putative relativistic component emitted in the accretion disk. [Results]: The average spectrum shows a highly significant iron feature. Estimating its equivalent width (EW) with a model-independent method suggests a higher EW in a broader range. The line, modelled as an unresolved Gaussian, is significant at 6.8σ and has an EW = 95 ± 22 eV for the full sample. We find that our current data can be fitted equally welladding a relativistic profile to the narrow component (in the full sample, EW = 140 ± 120 eV and 67 ± 28 eV respectively for the relativistic and narrow lines). [Conclusions]: Thanks to the high quality of the XMM CDFS spectra and to the detailed modelling of the continuum and instrumental effects, we have shown that the most distant AGN exhibit a highly significant iron emission feature. It can be modelled both with narrow and broad lines which suggest that the EW becomes higher when a broader energy range around the line centroid is considered, provides tantalising evidence for reflection by material both very close and far away from the central engine. The EW of both features are similar to those observed in individual nearby AGN, hence they must be a widespread characteristic of AGN, since otherwise the average values would be smaller than observed. © ESO, 2013., Financial support for this work was provided by the Spanish Ministry of Economy and Competitiveness through the grant AYA2010-21490-C02-01. We acknowledge financial contribution from the agreement ASI-INAF I/009/10/0 and from the PRIN-INAF 2011. P.R. acknowledges a grant from the Greek General Secretariat of Research and Technology in the framework of the programme Support of Postdoctoral Researchers.

[Context]: Accretion onto supermassive black holes is believed to occur mostly in obscured active galactic nuclei (AGN). Such objects are proving rather elusive in surveys of distant galaxies, including those at X-ray energies. [Aims]: Our main goal is to determine whether the revised IRAC criteria of Donley et al. (2012, ApJ, 748, 142; objects with an infrared (IR) power-law spectral shape), are effective at selecting X-ray type-2 AGN (i.e., absorbed N H > 1022 cm-2). [Methods]: We present the results from the X-ray spectral analysis of 147 AGN selected by cross-correlating the highest spectral quality ultra-deep XMM-Newton and the Spitzer/IRAC catalogues in the Chandra Deep Field South. Consequently it is biased towards sources with high S/N X-ray spectra. In order to measure the amount of intrinsic absorption in these sources, we adopt a simple X-ray spectral model that includes a power-law modified by intrinsic absorption at the redshift of each source and a possible soft X-ray component. [Results]: We find 21/147 sources to be heavily absorbed but the uncertainties in their obscuring column densities do not allow us to confirm their Compton-Thick nature without resorting to additional criteria. Although IR power-law galaxies are less numerous in our sample than IR non-power-law galaxies (60 versus 87 respectively), we find that the fraction of absorbed (NH intr > 1022 cm-2) AGN is significantly higher (at about 3 sigma level) for IR-power-law sources (∼2/3) than for those sources that do not meet this IR selection criteria (∼1/2). This behaviour is particularly notable at low luminosities, but it appears to be present, although with a marginal significance, at all luminosities. [Conclusions]: We therefore conclude that the IR power-law method is efficient in finding X-ray-absorbed sources. We would then expect that the long-sought dominant population of absorbed AGN is abundant among IR power-law spectral shape sources not detected in X-rays. © ESO, 2013., N.C.-M., F.J.C., S.M. and X.B. acknowledge financial support provided by the Spanish Ministry of Economy and Competitiveness through grant AYA2010-21490-C02-01. S.M., F.J.C. and A.A.-H. acknowledge financial support by the Spanish Ministry of Economy and Competitiveness through grants AYA2010-21490-C02-01 and AYA2012- 31447. SM acknowledges financial support from the JAE-Doc program (Consejo Superior de Investigaciones Científicas, cofunded by FSE). A.A.-H. acknowledges support from the Universidad de Cantabria through the Augusto G. Linares program. P.G.P.-G. acknowledges support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2009-07723-E and AYA2009- 10368. We acknowledge financial contribution from the agreement ASI-INAF I/009/10/0 and from the INAF-PRIN-2011.

[Context]: NGC 3147 is so far the most convincing case of a >true> Seyfert 2 galaxy, i.e. a source genuinely lacking the broad line regions. [Aims]: We obtained a Suzaku observation with the double aim to study in more detail the iron line complex, and to check the Compton-thick hypothesis for the lack of observed optical broad lines. [Methods]: The Suzaku XIS and HXD/PIN spectra of the source were analysed in detail. [Results]: The line complex is composed of at least two unresolved lines, one at about 6.45 keV and the other one at about 7 keV, most likely identified with Fe XVII/XIX, the former, and Fe XXVI, the latter. The high-ionization line can originate either in a photoionized matter or in an optically thin thermal plasma. In the latter case, an unusually high temperature is implied. In the photoionized model case, the large equivalent width can be explained either by an extreme iron overabundance or by assuming that the source is Compton-thick. In the Compton-thick hypothesis, however, the emission above 2 keV is mostly due to a highly ionized reflector, contrary to what is usually found in Compton-thick Seyfert 2s, where reflection from low ionized matter dominates. Moreover, the source flux varied between the XMM-Newton and the Suzaku observations, taken 3.5 years apart, confirming previous findings and indicating that the size of the emitting region must be smaller than a parsec. The hard X-ray spectrum is also inconclusive on the Compton-thick hypothesis. Weighting the various arguments, a >true> Seyfert 2 nature of NGC 3147 seems to be still the most likely explanation, even if the >highly ionized reflector> Compton-thick hypothesis cannot at present be formally rejected. © 2012 ESO., G.M., S.B. and F.P. acknowledge financial support from ASI under grants ASI/INAF I/088/06/0 and I/009/10/0, F.P. also from grant INTEGRAL I/033/10/0. X.B.’s research is funded by the Spanish Ministry of Economy and Competitivity through grant AYA2010-21490-C02-01.

We present the first results of the spectroscopy of distant, obscured AGN as obtained with the ultra-deep (~3.3 Ms) XMM-Newton survey in the Chandra Deep Field South (CDFS). One of the primary goals of the project is to characterize the X-ray spectral properties of obscured and heavily obscured Compton-thick AGN over the range of redhifts and luminosities that are relevant in terms of their contribution to the X-ray background. The ultra-deep exposure, coupled with the XMM detector's spectral throughput, allowed us to accumulate good quality X-ray spectra for a large number of X-ray sources and, in particular, for heavily obscured AGN at cosmological redshifts. Specifically we present the X-ray spectral properties of two high-redshift - z= 1.53 and z=3.70 - sources. The XMM spectra of both are very hard, with a strong iron Kalpha line at a rest-frame energy of 6.4 keV. A reflection-dominated continuum provides the best description of the X-ray spectrum of the z=1.53 source, while the intrinsic continuum of the z=3.70 AGN is obscured by a large column N_H ~ 10^24 cm-2 of cold gas. Compton-thick absorption, or close to it, is unambiguously detected in both sources. Interestingly, these sources would not be selected as candidate Compton thick AGN by some multiwavelength selection criteria based on the mid-infrared to optical and X-ray to optical flux ratios., Comment: 6 pages, 3 figures, 1 table. Minor changes applied to match the published version [A&A 526, L9 (2011)]

Hawkins reported on a class of 'naked' active galactic nuclei (AGN) characterized by strong amplitude optical brightness variability and the complete absence of broad emission lines in the optical spectrum. The variability suggests that the nucleus is seen directly, however the absence of broad lines contradicts the simple formulation of Unified Models for AGN. We present the results of quasi-simultaneous spectroscopic observations with XMM-Newton and New Technology Telescope (NTT) (La Silla) of two 'naked' AGN. We confirm the 'naked' nature of Q2131-427 for which no broad emission line components have been detected in the optical spectrum and its X-ray spectrum shows no signs of intrinsic absorption. The optical and X-ray mismatch in this source cannot be ascribed to a high nuclear dust-to-gas ratio and a Compton-thick nature is ruled out on the basis of the high FX/F [O iii] ratio. The broad-line region (BLR) may be completely absent in this source, possibly as a consequence of its low Eddington ratio. On the other hand, the optical spectrum of Q2130-431 shows Hα and Hβ broad emission line components, revealing the presence of a BLR. A mild X-ray absorption is expected in intermediate type 1.8 Seyfert galaxies like Q2130-431, however we put a very low upper limit on the column density (, FP acknowledges support by ASI-INAF I/08/07/0 grants. FJC and XB acknowledge support by the Spanish Ministry of Science and Innovation, under grants ESP2006-13608-C02-01. This work benefited from an Italian–Spanish Integrated Action (HI 2006-0079).

We present the results of the correlation between the nuclear 2-10 keV X-ray and radio (at 2 cm, 6 cm, and 20 cm) luminosities for a well-defined sample of local Seyfert galaxies. We use a sample of low luminosity radio galaxies (LLRGs) for comparison. In both Seyfert and LLRG samples, X-ray and radio luminosities are significantly correlated over 8 orders of magnitude, indicating that the X-ray and radio emission sources are strongly coupled. Moreover, both samples show a similar regression slope, LX L R 0.97, but Seyfert galaxies are three orders of magnitude less luminous in the radio band than LLRGs. This suggests that either similar physical mechanisms are responsible for the observed emission or a combination of different mechanisms ends up producing a similar correlation slope. Indeed, the common belief for LLRG is that both the X-ray and radio emission are likely dominated by a relativistic jet component, while in Seyfert galaxies the X-ray emission probably arises from a disk-corona system and the radio emission is attributed to a jet/outflow component. We investigate the radio loudness issue in the two samples and find that the Seyfert galaxies and the LLRGs show a different distribution of the radio loudness parameters. No correlation is found between the luminosity and the radio loudness; however, the latter is related to the black hole mass and anti-correlated with the Eddington ratio. The dichotomy in the radio loudness between Seyfert and LLRG observed down to low Eddington ratios, L2-10 keV/LEdd ∼ 10-8, does not support the idea that the origin of the radio loudness is due to a switch in the accretion mode., F.P. acknowledges support by a “Juan de la Cierva” fellowship. Financial support for F.P., X.B., and F.J.C. was provided by the Spanish Ministry of Education and Science, under project ESP2006-13608.

We investigate the relation between the X-ray nuclear emission, optical emission line, radio luminosity and black hole mass for a sample of nearby Seyfert galaxies. Strong linear correlations between the 2-10 keV and [OIII], radio luminosities have been found, showing the same slopes found in quasars and luminous Seyfert galaxies, thus implying independence from the level of nuclear activity displayed by the sources. Moreover, despite the wide range of Eddington ratios (L/L(Edd)) tested here (six orders of magnitude, from 0.1 down to 10^(-7), no correlation is found between the X-ray, optical emission lines, radio luminosities and the black hole mass. These results suggest that low luminosity Seyfert galaxies are a scaled down version of luminous AGN and probably are powered by the same physical processes., 6 pages, 3 figures, contributed talk presented at the Workshop "The multicoloured landscape of compact objects and their explosive origin", Cefalu' (Sicily), 11-24 June 2006, to be published by AIP