Intrinsic X-ray Luminosity Research Articles

NuSTARREVEALS EXTREME ABSORPTION INz< 0.5 TYPE 2 QUASARS

The intrinsic column density (NH) distribution of quasars is poorly known. At the high obscuration end of the quasar population and for redshifts z<1, the X-ray spectra can only be reliably characterized using broad-band measurements which extend to energies above 10 keV. Using the hard X-ray observatory NuSTAR, along with archival Chandra and XMM-Newton data, we study the broad-band X-ray spectra of nine optically selected (from the SDSS), candidate Compton-thick (NH > 1.5e24 cm^-2) type 2 quasars (CTQSO2s); five new NuSTAR observations are reported herein, and four have been previously published. The candidate CTQSO2s lie at z<0.5, have observed [OIII] luminosities in the range 8.4 < log (L_[OIII]/L_solar) < 9.6, and show evidence for extreme, Compton-thick absorption when indirect absorption diagnostics are considered. Amongst the nine candidate CTQSO2s, five are detected by NuSTAR in the high energy (8-24 keV) band: two are weakly detected at the ~ 3 sigma confidence level and three are strongly detected with sufficient counts for spectral modeling (>~ 90 net source counts at 8-24 keV). For these NuSTAR-detected sources direct (i.e., X-ray spectral) constraints on the intrinsic AGN properties are feasible, and we measure column densities ~2.5-1600 times higher and intrinsic (unabsorbed) X-ray luminosities ~10-70 times higher than pre-NuSTAR constraints from Chandra and XMM-Newton. Assuming the NuSTAR-detected type 2 quasars are representative of other Compton-thick candidates, we make a correction to the NH distribution for optically selected type 2 quasars as measured by Chandra and XMM-Newton for 39 objects. With this approach, we predict a Compton-thick fraction of f_CT = 36^{+14}_{-12} %, although higher fractions (up to 76%) are possible if indirect absorption diagnostics are assumed to be reliable.

DETAILED SHAPE AND EVOLUTIONARY BEHAVIOR OF THE X-RAY LUMINOSITY FUNCTION OF ACTIVE GALACTIC NUCLEI

We construct the rest-frame 2--10 keV intrinsic X-ray luminosity function of Active Galactic Nuclei (AGNs) from a combination of X-ray surveys from the all-sky Swift BAT survey to the Chandra Deep Field-South. We use ~3200 AGNs in our analysis, which covers six orders of magnitude in flux. The inclusion of the XMM and Chandra COSMOS data has allowed us to investigate the detailed behavior of the XLF and evolution. In deriving our XLF, we take into account realistic AGN spectrum templates, absorption corrections, and probability density distributions in photometric redshift. We present an analytical expression for the overall behavior of the XLF in terms of the luminosity-dependent density evolution, smoothed two power-law expressions in 11 redshift shells, three-segment power-law expression of the number density evolution in four luminosity classes, and binned XLF. We observe a sudden flattening of the low luminosity end slope of the XLF slope at z>~0.6. Detailed structures of the AGN downsizing have been also revealed, where the number density curves have two clear breaks at all luminosity classes above log LX>43. The two break structure is suggestive of two-phase AGN evolution, consisting of major merger triggering and secular processes.

OBSCURATION-DEPENDENT EVOLUTION OF ACTIVE GALACTIC NUCLEI

We aim to constrain the evolution of AGN as a function of obscuration using an X-ray selected sample of $\sim2000$ AGN from a multi-tiered survey including the CDFS, AEGIS-XD, COSMOS and XMM-XXL fields. The spectra of individual X-ray sources are analysed using a Bayesian methodology with a physically realistic model to infer the posterior distribution of the hydrogen column density and intrinsic X-ray luminosity. We develop a novel non-parametric method which allows us to robustly infer the distribution of the AGN population in X-ray luminosity, redshift and obscuring column density, relying only on minimal smoothness assumptions. Our analysis properly incorporates uncertainties from low count spectra, photometric redshift measurements, association incompleteness and the limited sample size. We find that obscured AGN with $N_{H}>{\rm 10^{22}\, cm^{-2}}$ account for ${77}^{+4}_{-5}\%$ of the number density and luminosity density of the accretion SMBH population with $L_{{\rm X}}>10^{43}\text{ erg/s}$, averaged over cosmic time. Compton-thick AGN account for approximately half the number and luminosity density of the obscured population, and ${38}^{+8}_{-7}\%$ of the total. We also find evidence that the evolution is obscuration-dependent, with the strongest evolution around $N_{H}\thickapprox10^{23}\text{ cm}^{-2}$. We highlight this by measuring the obscured fraction in Compton-thin AGN, which increases towards $z\sim3$, where it is $25\%$ higher than the local value. In contrast the fraction of Compton-thick AGN is consistent with being constant at $\approx35\%$, independent of redshift and accretion luminosity. We discuss our findings in the context of existing models and conclude that the observed evolution is to first order a side-effect of anti-hierarchical growth.

Revisiting the relationship between 6 μm and 2–10 keV continuum luminosities of AGN

We have determined the relation between the AGN luminosities at rest-frame 6 {\mu}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 {\mu}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 {\mu}m $\propto$ L_2-10 keV^0.99$\pm$0.032, with intrinsic scatter, ~0.35 dex in log L_6 {\mu}m. The L_6 {\mu}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 <12 {\mu}m and are overall ~1.3-2 times fainter at 6 {\mu}m than type 1 AGN at a given X-ray luminosity. Regardless of whether type 1 and type 2 AGN have the same or different nuclear dusty toroidal structures, our results imply that the AGN emission at rest-frame 6 {\mu}m is not isotropic due to self-absorption in the dusty torus, as predicted by AGN torus models. Thus, AGN surveys at rest-frame 6 {\mu}m are subject to modest dust obscuration biases.

Origin of X-ray Spectral Variation and the Seemingly Broad Iron-Line Spectral Feature in Seyfert Galaxies

We present systematic X-ray data analysis of the Seyfert galaxies observed by Suzaku to study origin of their hard X-ray (2 - 40 keV) variations. In particular, we examine if the "Variable Partial Covering (VPC) model" proposed by Miyakawa, Ebisawa and Inoue (2012), which was successful to explain spectral variations of MCG{6-30-15, is also valid for other Seyfert galaxies or not. In this model, intrinsic X-ray luminosity of the AGN is not signicantly variable, and most observed flux and spectral variations are caused by change of the geometrical covering fraction of the extended X-ray source by ionized absorbing clouds in the line of sight. We found that the observed flux and spectral variations of 20 targets in addition to MCG{6-30-15 are successfully explained by the VPC model. The transmitted spectral component through the absorbing clouds has a characteristics spectral feature of the ionized iron K-edge, which is considered to be the origin of the seemingly broad iron-line feature commonly observed in Seyfert galaxies. Variation of the partial covering fraction of the constant X-ray luminosity source causes such an anti-correlation between the direct (non-obscured) component and the transmitted (obscured) component, that cancels their variations each other. The cancellation works most effectively at the energy band where intensities of the two components are the closest to each other, namely, just below the iron K-edge. This explains the signicantly small fractional variations in the iron K-energy band, another well-known observational characteristic of Seyfert galaxies.

THENuSTARVIEW OF NEARBY COMPTON-THICK ACTIVE GALACTIC NUCLEI: THE CASES OF NGC 424, NGC 1320, AND IC 2560

We present X-ray spectral analyses for three Seyfert 2 active galactic nuclei, NGC 424, NGC 1320, and IC 2560, observed by NuSTAR in the 3-79 keV band. The high quality hard X-ray spectra allow detailed modeling of the Compton reflection component for the first time in these sources. Using quasi-simultaneous NuSTAR and Swift/XRT data, as well as archival XMM-Newton data, we find that all three nuclei are obscured by Compton-thick material with column densities in excess of ~5 x $10^{24}$ cm$^{-2}$, and that their X-ray spectra above 3 keV are dominated by reflection of the intrinsic continuum on Compton-thick material. Due to the very high obscuration, absorbed intrinsic continuum components are not formally required by the data in any of the sources. We constrain the intrinsic photon indices and the column density of the reflecting medium through the shape of the reflection spectra. Using archival multi-wavelength data we recover the intrinsic X-ray luminosities consistent with the broadband spectral energy distributions. Our results are consistent with the reflecting medium being an edge-on clumpy torus with a relatively large global covering factor and overall reflection efficiency of the order of 1%. Given the unambiguous confirmation of the Compton-thick nature of the sources, we investigate whether similar sources are likely to be missed by commonly used selection criteria for Compton-thick AGN, and explore the possibility of finding their high-redshift counterparts.

Feedback from winds and supernovae in massive stellar clusters – II. X-ray emission

The X-ray emission from a simulated massive stellar cluster is investigated. The emission is calculated from a 3D hydrodynamical model which incorporates the mechanical feedback from the stellar winds of 3 O-stars embedded in a giant molecular cloud clump containing 3240 M$_{\odot}$ of molecular material within a 4 pc radius. A simple prescription for the evolution of the stars is used, with the first supernova explosion at t=4.4 Myrs. We find that the presence of the GMC clump causes short-lived attenuation effects on the X-ray emission of the cluster. However, once most of the material has been ablated away by the winds the remaining dense clumps do not have a noticable effect on the attenuation compared with the assumed interstellar medium column. We determine the evolution of the cluster X-ray luminosity, L$_X$, and spectra, and generate synthetic images. The intrinsic X-ray luminosity drops from nearly 10$^{34}$ ergs s$^{-1}$ while the winds are `bottled up', to a near constant value of 1.7$\times 10^{32}\rm ergs s^{-1}$ between t=1-4 Myrs. L$_X$ reduces slightly during each star's red supergiant stage due to the depressurization of the hot gas. However, L$_X$ increases to $\approx 10^{34}\rm\,ergs s^{-1}$ during each star's Wolf-Rayet stage. The X-ray luminosity is enhanced by 2-3 orders of magnitude to $\sim 10^{37}\rm ergs s^{-1}$ for at least 4600 yrs after each supernova, at which time the blast wave leaves the grid and the X-ray luminosity drops. The X-ray luminosity of our simulation is generally considerably fainter than predicted from spherically-symmetric bubble models, due to the leakage of hot gas material through gaps in the outer shell. This process reduces the pressure within our simulation and thus the X-ray emission. However, the X-ray luminosities and temperatures which we obtain are comparable to similarly powerful massive young clusters.

NuSTARREVEALS AN INTRINSICALLY X-RAY WEAK BROAD ABSORPTION LINE QUASAR IN THE ULTRALUMINOUS INFRARED GALAXY MARKARIAN 231

We present high-energy (3--30 keV) {\it NuSTAR} observations of the nearest quasar, the ultraluminous infrared galaxy (ULIRG) Markarian 231 (Mrk 231), supplemented with new and simultaneous low-energy (0.5--8 keV) data from {\it Chandra}. The source was detected, though at much fainter levels than previously reported, likely due to contamination in the large apertures of previous non-focusing hard X-ray telescopes. The full band (0.5--30 keV) X-ray spectrum suggests the active galactic nucleus (AGN) in Mrk 231 is absorbed by a patchy and Compton-thin (N$_{\rm H} \sim1.2^{+0.3}_{-0.3}\times10^{23}$ cm$^{-2}$) column. The intrinsic X-ray luminosity (L$_{\rm 0.5-30 keV}\sim1.0\times10^{43}$ erg s$^{1}$) is extremely weak relative to the bolometric luminosity where the 2--10 keV to bolometric luminosity ratio is $\sim$0.03% compared to the typical values of 2--15%. Additionally, Mrk 231 has a low X-ray-to-optical power law slope ($\alpha_{\rm OX}\sim-1.7$). It is a local example of a low-ionization broad absorption line (LoBAL) quasar that is intrinsically X-ray weak. The weak ionizing continuum may explain the lack of mid-infrared [O IV], [Ne V], and [Ne VI] fine-structure emission lines which are present in sources with otherwise similar AGN properties. We argue that the intrinsic X-ray weakness may be a result of the super-Eddington accretion occurring in the nucleus of this ULIRG, and may also be naturally related to the powerful wind event seen in Mrk 231, a merger remnant escaping from its dusty cocoon.

SN 2005ip: A LUMINOUS TYPE IIn SUPERNOVA EMERGING FROM A DENSE CIRCUMSTELLAR MEDIUM AS REVEALED BY X-RAY OBSERVATIONS

We report on X-ray spectral evolution of the nearby Type IIn supernova (SN) 2005ip, based on Chandra and Swift observations covering from ~1 to 6 years after the explosion. X-ray spectra in all epochs are well fitted by a thermal emission model with kT > 7 keV. The somewhat high temperature suggests that the X-ray emission mainly arises from the circumstellar medium heated by the forward shock. We find that the spectra taken 2-3 years since the explosion are heavily absorbed N_H ~ 5e22 cm^{-2}, but the absorption gradually decreases to the level of the Galactic absorption N_H ~ 4e20 cm^{-2} at the final epoch. This indicates that the SN went off in a dense circumstellar medium and that the forward shock has overtaken it. The intrinsic X-ray luminosity stays constant until the final epoch when it drops by a factor of ~2. The intrinsic 0.2-10 keV luminosity during the plateau phase is measured to be ~1.5e41 erg/s, ranking SN 2005ip as one of the brightest X-ray SNe. Based on the column density, we derive a lower-limit of a mass-loss rate to be M_dot ~ 0.015 (V_w/100 km/s) M_sun/yr, which roughly agrees with that inferred from the X-ray luminosity, M_dot ~ 0.02 (V_w/100 km/s) M_sun/yr, where V_w is the circumstellar wind speed. Such a high mass-loss rate suggests that the progenitor star had eruptive mass ejections like a luminous blue variable star. The total mass ejected in the eruptive period is estimated to be ~15 M_sun, indicating that the progenitor mass is greater than ~25 M_sun.

The incidence of obscuration in active galactic nuclei

We study the incidence of nuclear obscuration on a complete sample of 1310 AGN selected on the basis of their rest-frame 2-10 keV X-ray flux from the XMM-COSMOS survey, in the redshift range 0.3<z<3.5. We classify the AGN as obscured or un-obscured on the basis of either the optical spectral properties and the overall SED or the shape of the X-ray spectrum. The two classifications agree in about 70% of the objects, and the remaining 30% can be further subdivided into two distinct classes: at low luminosities X-ray un-obscured AGN do not always show signs of broad lines or blue/UV continuum emission in their optical spectra, most likely due to galaxy dilution effects; at high luminosities broad line AGN may have absorbed X-ray spectra, which hints at an increased incidence of small-scale (sub-parsec) dust-free obscuration. We confirm that the fraction of obscured AGN is a decreasing function of the intrinsic X-ray luminosity, while the incidence of absorption shows significant evolution only for the most luminous AGN, which appear to be more commonly obscured at higher redshift. We find no significant difference between the mean stellar masses and star formation rates of obscured and un-obscured AGN hosts. We conclude that the physical state of the medium responsible for obscuration in AGN is complex, and mainly determined by the radiation environment (nuclear luminosity) in a small region enclosed within the gravitational sphere of influence of the central black hole, but is largely insensitive to the wider scale galactic conditions.

New Compton-thick AGN in the circumnuclear H2O maser hosts UGC 3789 and NGC 6264

Large column densities, derived from X-ray studies, are typically measured towards AGN hosting water masers, especially when the H2O emission is associated with the nuclear accretion disk. In addition, possible correlations between the intrinsic X-ray luminosity and the characteristics of the H2O maser emission have been put forward that, however, require confirmation. We have performed high-sensitivity XMM-Newton observations of a sample of five H2O maser sources confidently detected in our ongoing survey with the Swift satellite of all known water masers in AGN, in order to obtain detailed X-ray information of these promising targets and to set up a systematic detailed study of the X-ray/H2O-maser relation in AGN. For three galaxies, NGC 613, VIIZw73, and IRAS 16288+3929, the amount of intrinsic absorption has been estimated, indicating column densities of 4-6x10^23 cm^-2. For UGC 3789 and NGC 6264 (the two confirmed disk-maser galaxies in our sample), column densities in excess of 1x10^24 cm^-2 are inferred from the large EW of the Fe Kalpha line. By adding our results to those obtained in past similar studies, we find that the percentage of water masers sources that host highly-obscured (NH>10^23 cm^-2) and Compton-thick AGN is 96% (45/47) and 57% (27/47), respectively. In addition, 86%, 18/21, of disk maser galaxies host Compton-thick AGN. The correlation between the galaxies' bolometric luminosity and accretion disk radius, suggested in previous works, is also confirmed.

Calibrated estimates of the energy in major flares of GRS 1915+105

We analyze the energetics of the major radio flare of October 8 2005 in GRS 1915+105. The flare is of particular interest because it is one of the most luminous and energetic radio flares from a Galactic black hole that has ever been observed. The motivation is two-fold. One, to learn more about the energetics of this most extreme phenomenon and its relationship to the accretion state. The second is to verify if the calibrated estimates of the energy of major radio flares (based on the peak low frequency optically thin flux) derived from flares in the period 1996-2001 in Punsly & Rodriguez (2013), PR13 hereafter, can be used to estimate plasmoid energy beyond this time period. We find evidence that the calibrated curves are still accurate for this strong flare. Furthermore, the physically important findings of PR13 are supported by the inclusion of this flare: the flare energy is correlated with both the intrinsic bolometric X-ray luminosity, $L_{\mathrm{bol}}$, $\sim 1$ hour before ejection and $L_{\mathrm{bol}}$ averaged over the duration of the ejection of the plasmoid and $L_{\mathrm{bol}}$ is highly elevated relative to historic levels just before and during the ejection episode. A search of the data archives reveal that only the October 8 2005 flare and those in PR13 have adequate data sampling to allow estimates of both the energy of the flare and the X-ray luminosity before and during flare launch.

GRS 1915+105 AS A GALACTIC ANALOG OF A FANAROFF-RILEY II QUASAR

We study the long term time averaged kinetic luminosity, $\bar{Q}$, of the major flares of the Galactic microquasar GRS 1915+105 and the relationship to the intrinsic X-ray (bolometric) luminosity, $L_{\mathrm{bol}}$, and scale it to that of a complete sample of SDSS/FIRST FR II quasars. If the scale invariance hypothesis for black holes (BHs) holds then we show that the expected distribution in the $\bar{Q}$ - $L_{\mathrm{bol}}$ scatter plane of GRS 1915+105 is consistent with FR II quasars for distances D = 10.7 - 11 kpc. We compare the specific values of kinetic luminosity and $L_{\mathrm{bol}}$ during flares of GRS 1915+105 to that predicted by several 3-D MHD simulations of BH accretion flows with relativistic ejections. If FR II quasars are a scaled up version of GRS 1915+105, the data are consistent with numerical models when they contain an ergospheric disk jet and the BH spin is $a/M= 0.99$ or $a/M=0.998$ (we estimate $a/M>0.984$). In the framework of scale invariance of BHs, our results may imply that FR II quasars also hold rapidly rotating BHs.

SELF-REGULATED SHOCKS IN MASSIVE STAR BINARY SYSTEMS

In an early-type, massive star binary system, X-ray bright shocks result from the powerful collision of stellar winds driven by radiation pressure on spectral line transitions. We examine the influence of the X-rays from the wind-wind collision shocks on the radiative driving of the stellar winds using steady state models that include a parameterized line force with X-ray ionization dependence. Our primary result is that X-ray radiation from the shocks inhibits wind acceleration and can lead to a lower pre-shock velocity, and a correspondingly lower shocked plasma temperature, yet the intrinsic X-ray luminosity of the shocks, LX remains largely unaltered, with the exception of a modest increase at small binary separations. Due to the feedback loop between the ionizing X-rays from the shocks and the wind-driving, we term this scenario as self regulated shocks. This effect is found to greatly increase the range of binary separations at which a wind-photosphere collision is likely to occur in systems where the momenta of the two winds are significantly different. Furthermore, the excessive levels of X-ray ionization close to the shocks completely suppresses the line force, and we suggest that this may render radiative braking less effective. Comparisons of model results against observations reveals reasonable agreement in terms of log(LX/Lbol). The inclusion of self regulated shocks improves the match for kT values in roughly equal wind momenta systems, but there is a systematic offset for systems with unequal wind momenta (if considered to be a wind-photosphere collision).

THE RELATIONSHIP BETWEEN X-RAY LUMINOSITY AND MAJOR FLARE LAUNCHING IN GRS 1915+105

We perform the most detailed analysis to date of the X-ray state of the Galactic black hole candidate GRS 1915+105 just prior to (0 to 4 hours) and during the brief (1 to 7 hour) ejection of major (superluminal) radio flares. A very strong model independent correlation is found between the 1.2 keV - 12 keV X-ray flux 0 to 4 hours before flare ejections with the peak optically thin 2.3 GHz emission of the flares. This suggests a direct physical connection between the energy in the ejection and the luminosity of the accretion flow preceding the ejection. In order to quantify this concept, we develop techniques to estimate the intrinsic (unabsorbed) X-ray luminosity, $L_{\mathrm{intrinsic}}$, from RXTE ASM data and to implement known methods to estimate the time averaged power required to launch the radio emitting plasmoids, $Q$ (sometimes called jet power). We find that the distribution of intrinsic luminosity from 1.2 keV - 50 keV, $L_{\mathrm{intrinsic}}(1.2 - 50)$, is systematically elevated just before ejections compared to arbitrary times when there are no major ejections. The estimated $Q$ is strongly correlated with $L_{\mathrm{intrinsic}}(1.2 - 50)$ 0 to 4 hours before the ejection, the increase in $L_{\mathrm{intrinsic}}(1.2 - 50)$ in the hours preceding the ejection and the time averaged $L_{\mathrm{intrinsic}}(1.2 - 50)$ during the flare rise. Furthermore, the total time averaged power during the ejection ($Q$ + the time average of $L_{\mathrm{intrinsic}}(1.2 - 50)$ during ejection) is strongly correlated with $L_{\mathrm{intrinsic}}(1.2 - 50)$ just before launch with near equality if the distance to the source is $ \approx 10.5$ kpc.

THE LINK BETWEEN THE HIDDEN BROAD LINE REGION AND THE ACCRETION RATE IN SEYFERT 2 GALAXIES

In the past few years more and more pieces of evidence have been presented for a revision of the widely accepted Unified Model of Active Galactic Nuclei. A model based solely on orientation cannot explain all the observed phenomenology. In the following, we will present evidence that accretion rate is also a key parameter for the presence of Hidden Broad Line Regions in Seyfert 2 galaxies. Our sample consists of 21 sources with polarized Hidden Broad Lines and 18 sources without Hidden Broad Lines. We use stellar velocity dispersions from several studies on the CaII and Mg b triplets in Seyfert 2 galaxies, to estimate the mass of the central black holes via the Mbh-{\sigma}\ast relation. The ratio between the bolometric luminosity, derived from the intrinsic (i.e. unabsorbed) X-ray luminosity, and the Eddington luminosity is a measure of the rate at which matter accretes onto the central supermassive black hole. A separation between Compton-thin HBLR and non-HBLR sources is clear, both in accretion rate (log Lbol/LEdd = -1.9) and in luminosity (log Lbol = 43.90). When, properly luminosity-corrected, Compton-thick sources are included, the separation between HBLR and non-HBLR is less sharp but no HBLR source falls below the Eddington ratio threshold. We speculate that non-HBLR Compton-thick sources with accretion rate higher than the threshold, do possess a BLR, but something, probably related to their heavy absorption, is preventing us from observing it even in polarized light. Our results for Compton-thin sources support theoretical expectations. In a model presented by Nicastro (2000), the presence of broad emission lines is intrinsically connected with disk instabilities occuring in proximity of a transition radius, which is a function of the accretion rate, becoming smaller than the innermost stable orbit for very low accretion rates and therefore luminosities.

Planckearly results. X. Statistical analysis of Sunyaev-Zeldovich scaling relations for X-ray galaxy clusters

All-sky data from the Planck survey and the Meta-Catalogue of X-ray detected Clusters of galaxies (MCXC) are combined to investigate the relationship between the thermal Sunyaev-Zeldovich (SZ) signal and X-ray luminosity. The sample comprises ~ 1600 X-ray clusters with redshifts up to ~ 1 and spans a wide range in X-ray luminosity. The SZ signal is extracted for each object individually, and the statistical significance of the measurement is maximised by averaging the SZ signal in bins of X-ray luminosity, total mass, or redshift. The SZ signal is detected at very high significance over more than two decades in X-ray luminosity (10^43 erg/s < L_500 E(z)^-7/3 < 2 X 10^45 erg/s). The relation between intrinsic SZ signal and X-ray luminosity is investigated and the measured SZ signal is compared to values predicted from X-ray data. Planck measurements and X-ray based predictions are found to be in excellent agreement over the whole explored luminosity range. No significant deviation from standard evolution of the scaling relations is detected. For the first time the intrinsic scatter in the scaling relation between SZ signal and X-ray luminosity is measured and found to be consistent with the one in the luminosity -- mass relation from X-ray studies. There is no evidence of any deficit in SZ signal strength in Planck data relative to expectations from the X-ray properties of clusters, underlining the robustness and consistency of our overall view of intra-cluster medium properties.

Suzaku X-ray spectral study of the Compton-thick Seyfert galaxy NGC 5135

We present the 0.5 - 50 keV Suzaku broad-band X-ray spectral study of the Compton-thick AGN in NGC 5135. The Suzaku observation provides the first detection of NGC 5135 above 10 keV that allowed us, for the first time, to estimate the absorbing column density, the intrinsic X-ray luminosity, the strength of the reflection component and the viewing angle of the torus for this AGN. The 0.5 - 10 keV spectrum of NGC 5135 is characterized by the standard components for a Compton-thick source: a scattered continuum, a prominent Fe K{\alpha} emission line (EW ~ 2.1 keV) and a soft excess. At higher energies (E > 10 keV) the intrinsic AGN continuum shows up, implying an absorbing column density of the order of ~ 2.5 \times 10^24 cm^-2 and the intrinsic 2.0 - 10 keV X-ray luminosity of ~ 1.8 \times 10^43 erg s^-1. Assuming a toroidal geometry of the reprocessing material we show that an edge-on view of the obscuring torus is preferred in this source.

REVEALING A POPULATION OF HEAVILY OBSCURED ACTIVE GALACTIC NUCLEI ATz≈ 0.5-1 IN THE CHANDRA DEEP FIELD-SOUTH

(abridged) We identify a numerically significant population of heavily obscured AGNs at z~0.5-1 in the Chandra Deep Field-South (CDF-S) and Extended Chandra Deep Field-South by selecting 242 X-ray undetected objects with infrared-based star formation rates (SFRs) substantially higher (a factor of 3.2 or more) than their SFRs determined from the UV after correcting for dust extinction. An X-ray stacking analysis of 23 candidates in the central CDF-S region using the 4 Ms Chandra data reveals a hard X-ray signal with an effective power-law photon index of Gamma=0.6_{-0.4}^{+0.3}, indicating a significant contribution from obscured AGNs. Based on Monte Carlo simulations, we conclude that 74+-25% of the selected galaxies host obscured AGNs, within which ~95% are heavily obscured and ~80% are Compton-thick (CT; NH>1.5x10^{24} cm^{-2}). The heavily obscured objects in our sample are of moderate intrinsic X-ray luminosity [ ~ (0.9-4)x10^{42} erg/s in the 2-10 keV band]. The space density of the CT AGNs is (1.6+-0.5)x10^{-4} Mpc^{-3}. The z~0.5-1 CT objects studied here are expected to contribute ~1% of the total XRB flux in the 10-30 keV band, and they account for ~5-15% of the emission in this energy band expected from all CT AGNs according to population-synthesis models. In the 6--8 keV band, the stacked signal of the 23 heavily obscured candidates accounts for <5% of the unresolved XRB flux, while the unresolved ~25% of the XRB in this band can probably be explained by a stacking analysis of the X-ray undetected optical galaxies in the CDF-S (a 2.5 sigma stacked signal). We discuss prospects to identify such heavily obscured objects using future hard X-ray observatories.

PHYSICAL STRUCTURE OF THE PLANETARY NEBULA NGC 3242 FROM THE HOT BUBBLE TO THE NEBULAR ENVELOPE

One key feature of the interacting stellar winds model of the formation of planetary nebulae (PNe) is the presence of shock-heated stellar wind confined in the central cavities of PNe. This so-called hot bubble should be detectable in X-rays. Here we present XMM-Newton observations of NGC 3242, a multiple-shell PN whose shell morphology is consistent with the interacting stellar winds model. Diffuse X-ray emission is detected within its inner shell with a plasma temperature ~2.35\times10^6 K and an intrinsic X-ray luminosity ~2\times10^30 ergs s^(-1) at the adopted distance of 0.55 kpc. The observed X-ray temperature and luminosity are in agreement with "ad-hoc" predictions of models including heat conduction. However, the chemical abundances of the X-ray-emitting plasma seem to imply little evaporation of cold material into the hot bubble, whereas the thermal pressure of the hot gas is unlikely to drive the nebular expansion as it is lower than that of the inner shell rim. These inconsistencies are compounded by the apparent large filling factor of the hot gas within the central cavity of NGC 3242. Subject headings: planetary nebulae: individual (NGC 3242)