We present an X-ray point-source catalogue from the XMM-Large Scale Structure (XMMLSS) survey region, one of the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) fields. We target ...the XMM-LSS region with 1.3 Ms of new XMM-Newton AO-15 observations, transforming the archival X-ray coverage in this region into a 5.3 deg2 contiguous field with uniform X-ray coverage totaling 2.7 Ms of flare-filtered exposure, with a 46 ks median PN exposure time. We provide an X-ray catalogue of 5242 sources detected in the soft (0.5-2 keV), hard (2-10 keV), and/or full (0.5-10 keV) bands with a 1 per cent expected spurious fraction determined from simulations. A total of 2381 new X-ray sources are detected compared to previous source catalogues in the same area. Our survey has flux limits of 1.7 × 10-15, 1.3 × 10-14, and 6.5 × 10-15 erg cm-2 s-1 over 90 per cent of its area in the soft, hard, and full bands, respectively, which is comparable to those of the XMM-COSMOS survey. We identify multiwavelength counterpart candidates for 99.9 per cent of the X-ray sources, of which 93 per cent are considered as reliable based on their matching likelihood ratios. The reliabilities of these high-likelihood-ratio counterparts are further confirmed to be ≈97 per cent reliable based on deep Chandra coverage over ≈5 per cent of the XMM-LSS region. Results of multiwavelength identifications are also included in the source catalogue, along with basic optical-to-infrared photometry and spectroscopic redshifts from publicly available surveys. We compute photometric redshifts for X-ray sources in 4.5 deg2 of our field where forced-aperture multiband photometry is available; > 70 per cent of the X-ray sources in this subfield have either spectroscopic or high-quality photometric redshifts.
The active galactic nuclei (AGN) X-ray luminosity function traces actively accreting supermassive black holes and is essential for the study of the properties of the AGN population, black hole ...evolution, and galaxy-black hole coevolution. Up to now, the AGN luminosity function has been estimated several times in soft (0.5−2 keV) and hard X-rays (2−10 keV). AGN selection in these energy ranges often suffers from identification and redshift incompleteness and, at the same time, photoelectric absorption can obscure a significant amount of the X-ray radiation. We estimate the evolution of the luminosity function in the 5−10 keV band, where we effectively avoid the absorbed part of the spectrum, rendering absorption corrections unnecessary up to NH ~ 1023 cm-2. Our dataset is a compilation of six wide, and deep fields: MAXI, HBSS, XMM-COSMOS, Lockman Hole, XMM-CDFS, AEGIS-XD, Chandra-COSMOS, and Chandra-CDFS. This extensive sample of ~1110 AGN (0.01 < z < 4.0, 41 < log Lx < 46) is 98% redshift complete with 68% spectroscopic redshifts. For sources lacking a spectroscopic redshift estimation we use the probability distribution function of photometric redshift estimation specifically tuned for AGN, and a flat probability distribution function for sources with no redshift information. We use Bayesian analysis to select the best parametric model from simple pure luminosity and pure density evolution to more complicated luminosity and density evolution and luminosity-dependent density evolution (LDDE). We estimate the model parameters that describe best our dataset separately for each survey and for the combined sample. We show that, according to Bayesian model selection, the preferred model for our dataset is the LDDE. Our estimation of the AGN luminosity function does not require any assumption on the AGN absorption and is in good agreement with previous works in the 2−10 keV energy band based on X-ray hardness ratios to model the absorption in AGN up to redshift three. Our sample does not show evidence of a rapid decline of the AGN luminosity function up to redshift four.
We present the X-ray spectroscopic study of the Compton-thick (CT) active galactic nuclei (AGN) population within the Chandra Deep Field South (CDF-S) by using the deepest X-ray observation to date, ...the Chandra 7 Ms observation of the CDF-S. We combined an optimized version of our automated selection technique and a Bayesian Monte Carlo Markov chains (MCMC) spectral fitting procedure, to develop a method to pinpoint and then characterize candidate CT AGN as less model dependent and/or data-quality dependent as possible. To obtain reliable automated spectral fits, we only considered the sources detected in the hard (2−8 keV) band from the CDF-S 2 Ms catalog with either spectroscopic or photometric redshifts available for 259 sources. Instead of using our spectral analysis to decide if an AGN is CT, we derived the posterior probability for the column density, and then we used it to assign a probability of a source being CT. We also tested how the model-dependence of the spectral analysis, and the spectral data quality, could affect our results by using simulations. We finally derived the number density of CT AGN by taking into account the probabilities of our sources being CT and the results from the simulations. Our results are in agreement with X-ray background synthesis models, which postulate a moderate fraction (25%) of CT objects among the obscured AGN population.
Heavily obscured, Compton thick (CT, NH> 1024 cm-2) active galactic nuclei (AGN) may represent an important phase in AGN/galaxy co-evolution and are expected to provide a significant contribution to ...the cosmic X-ray background at its peak. However, unambiguously identifying CT AGN beyond the local Universe is a challenging task even in the deepest X-ray surveys, and given the expected low spatial density of these sources in the 2−10 keV band, large area surveys are needed to collect sizable samples. Through direct X-ray spectra analysis, we selected 39 heavily obscured AGN (NH>3 × 1023 cm-2) at bright X-ray fluxes (F2−10 ≳ 10-14 erg s-1 cm-2) in the 2 deg2 XMM-COSMOS survey. After selecting CT AGN based on the fit of a simple absorbed two power law model to the shallow XMM-Newton data, the presence of bona fide CT AGN was confirmed in 80% of the sources using deeper Chandra data and more complex models. The final sample comprises ten CT AGN (six of them also have a detected Fe Kα line with EW ~ 1 keV), spanning a wide range of redshifts (z ~ 0.1−2.5) and luminosity (L2−10 ~ 1043.5−1045 erg s-1) and is complemented by 29 heavily obscured AGN spanning the same redshift and luminosity range. We collected the rich multi-wavelength information available for all these sources, in order to study the distribution of super massive black hole and host properties, such as black hole mass (MBH), Eddington ratio (λEdd), stellar mass (M∗), specific star formation rate (sSFR) in comparison with a sample of unobscured AGN. We find that highly obscured sources tend to have significantly smaller MBH and higher λEdd with respect to unobscured sources, while a weaker evolution in M∗ is observed. The sSFR of highly obscured sources is consistent with the one observed in the main sequence of star forming galaxies, at all redshifts. We also present and briefly discuss optical spectra, broadband spectral energy distribution (SED) and morphology for the sample of ten CT AGN. Both the optical spectra and SED agree with the classification as highly obscured sources: all the available optical spectra are dominated by the stellar component of the host galaxy, and to reproduce the broadband SED, a highly obscured torus component is needed for all the CT sources.Exploiting the high resolution Hubble-ACS images available, we are able to show that these highly obscured sources have a significantly larger merger fraction with respect to other X-ray selected samples of AGN. Finally we discuss the implications of our findings in the context of AGN/galaxy co-evolutionary models, and compare our results with the predictions of X-ray background synthesis models.
Context.
High-ionisation lines in the soft X-ray band are generally associated to either interstellar hot gas along the line of sight or to photoionised gas intrinsic to the source. In the low-mass ...X-ray binary 4U 1820-30, the nature of these lines is not well understood.
Aims.
We aim to characterise the ionised gas present along the line of sight towards 4U 1820-30 producing the X-ray absorption lines of Mg
XI
, Ne
IX
, Fe
XVII
, O
VII
, and O
VIII
.
Methods.
We analysed all the observations available for this source in the
XMM-Newton
and
Chandra
archives that were taken with the RGS, HETG, and LETG spectrometers. We accurately examined the high-resolution grating spectra using a standard X-ray analysis procedure based on the
C
-statistic and using Bayesian parameter inference. We tested two physical models which describe a plasma in either collisional ionisation or photoionisation equilibrium. We adopted the Bayesian model comparison to statistically compare the different combinations of models used for the analysis.
Results.
We find that the lines are consistent with hot gas in the interstellar medium rather than the intrinsic gas of the X-ray binary. Our best-fit model reveals the presence of a collisionally ionised plasma with a temperature of
T
= (1.98 ± 0.05) × 10
6
K. The photoionisation model fails to fit the Fe
XVII
line (which is detected with a significance of 6.5
σ
) because of the low column density predicted by the model. Moreover, the low inclination of the binary system is likely the reason for the non-detection of ionised gas intrinsic to the source.
ABSTRACT
In this paper we investigate the power spectrum of the unresolved 0.5–2 keV cosmic X‐ray background (CXB) with deep Chandra 4‐Msec (Ms) observations in the Chandra Deep Field South (CDFS). ...We measured a signal that, on scales >30 arcsec, is significantly higher than the shot noise and is increasing with angular scale. We interpreted this signal as the joint contribution of clustered undetected sources like active galactic nuclei (AGN), galaxies and the intergalactic medium (IGM). The power of unresolved cosmic source fluctuations accounts for ∼12 per cent of the 0.5–2 keV extragalactic CXB. Overall, our modelling predicts that ∼20 per cent of the unresolved CXB flux is produced by low‐luminosity AGN, ∼25 per cent by galaxies and ∼55 per cent by the IGM. We do not find any direct evidence of the so‐called ‘warm hot intergalactic medium’ (i.e. matter with 105 < T < 107 K and density contrast δ < 1000), but we estimated that it could produce about 1/7 of the unresolved CXB. We placed an upper limit on the space density of postulated X‐ray‐emitting early black holes at z > 7.5 and compared it with supermassive black hole evolution models.
A deep X-ray observation of M82 with XMM–Newton Ranalli, P.; Comastri, A.; Origlia, L. ...
Monthly notices of the Royal Astronomical Society,
20/May , Letnik:
386, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We report on the analysis of a deep (100-ks) observation of the starburst galaxy M82 with the EPIC and RGS instruments onboard the X-ray telescope XMM–Newton. The broad-band (0.5–10 keV) emission is ...due to at least three spectral components: (i) continuum emission from point sources; (ii) thermal plasma emission from hot gas; and (iii) charge-exchange emission from neutral metals (Mg and Si). The plasma emission has a double-peaked differential emission measure, with the peaks at ∼0.5 and ∼7 keV. Spatially resolved spectroscopy has shown that the chemical absolute abundances are not uniformly distributed in the outflow, but are larger in the outskirts and smaller close to the galaxy centre. The abundance ratios also show spatial variations. The X-ray-derived oxygen abundance is lower than that measured in the atmospheres of red supergiant stars, leading to the hypothesis that a significant fraction of oxygen ions have already cooled off and no longer emit at energies ≳0.5 keV.
Summary
Background
Essential thrombocythemia (ET) is characterized by increased platelets and prevalent thrombosis. An acquired von Willebrand factor (VWF) disease has been hypothesized and ...inconsistently associated with extreme thrombocytosis or rare bleeding in ET. Whether VWF is modified in ET patients with controlled platelet count remains unclear.
Objectives
We studied different VWF‐ and platelet‐associated parameters in ET patients treated according to current recommendations.
Patients/Methods
Sixty‐nine ET patients (M = 29; median age, 62 48–70 years; platelets, 432 337–620 × 103 μL−1), 69 matched controls and 10 subjects with reactive thrombocytosis (RT) were studied. VWF:antigen (Ag), activity (act), electrophoretic patterns, VWF:propeptide, plasma glycocalycin (GC), glycoproteinV (GpV), ADAMTS‐13, elastase, C‐reactive protein and serum thromboxane (TX)B2 were measured.
Results
In ET patients, VWF:Ag was increased by 31 ± 13% vs. controls (P < 0.01), without dependence of blood groups, while VWF:act was reduced by 21 ± 12% vs. controls and by 50 ± 24% vs. RT (P < 0.01). The VWF:act/VWF:Ag ratios in ET were reduced by 35 ± 17% vs. controls and RT patients (P < 0.001) and significantly associated with: immature or total platelet counts, GC, GpV and TXB2. In multivariable analysis, only GC inversely predicted ET patients’ VWF:act/VWF:Ag ratios (β = −0.42, P = 0.01). By electrophoresis analyses, high‐molecular‐weight VWF multimers were variably reduced with atypical cleavage bands in ET only. VWF:propeptide, ADAMTS‐13 and elastase levels were normal in ET patients. Platelet‐associated ADAM‐10 and ADAM‐17 hydrolyzed VWFm in vitro, showing patterns similar to those in ET samples.
Conclusions
In ET patients with controlled platelet counts, the VWF:act/VWF:Ag ratio is decreased and predicted by GC, a product of platelet activation. ADAM‐10 and/or ADAM‐17 might be involved. In vivo platelet activation, which characterizes ET, might contribute to disease‐specific VWF alterations.
Aims. We present the detection, identification and calibration of extended sources in the deepest X-ray dataset to date, the Extended Chandra Deep Field South (ECDF-S). Methods. Ultra-deep ...observations of ECDF-S with Chandra and XMM-Newton enable a search for extended X-ray emission down to an unprecedented flux of 2 × 10-16 ergs s-1 cm-2. By using simulations and comparing them with the Chandra and XMM data, we show that it is feasible to probe extended sources of this flux level, which is 10 000 times fainter than the first X-ray group catalogs of the ROSAT all sky survey. Extensive spectroscopic surveys at the VLT and Magellan have been completed, providing spectroscopic identification of galaxy groups to high redshifts. Furthermore, available HST imaging enables a weak-lensing calibration of the group masses. Results. We present the search for the extended emission on spatial scales of 32′′ in both Chandra and XMM data, covering 0.3 square degrees and model the extended emission on scales of arcminutes. We present a catalog of 46 spectroscopically identified groups, reaching a redshift of 1.6. We show that the statistical properties of ECDF-S, such as log N − log S and X-ray luminosity function are broadly consistent with LCDM, with the exception that dn/dz/dΩ test reveals that a redshift range of 0.2 < z < 0.5 in ECDF-S is sparsely populated. The lack of nearby structure, however, makes studies of high-redshift groups particularly easier both in X-rays and lensing, due to a lower level of clustered foreground. We present one and two point statistics of the galaxy groups as well as weak-lensing analysis to show that the detected low-luminosity systems are indeed low-mass systems. We verify the applicability of the scaling relations between the X-ray luminosity and the total mass of the group, derived for the COSMOS survey to lower masses and higher redshifts probed by ECDF-S by means of stacked weak lensing and clustering analysis, constraining any possible departures to be within 30% in mass. Conclusions. Ultra-deep X-ray surveys uniquely probe the low-mass galaxy groups across a broad range of redshifts. These groups constitute the most common environment for galaxy evolution. Together with the exquisite data set available in the best studied part of the Universe, the ECDF-S group catalog presented here has an exceptional legacy value.
The XMM deep survey in the CDF-S Georgantopoulos, I; Comastri, A; Vignali, C ...
Astronomy and astrophysics (Berlin),
07/2013, Letnik:
555
Journal Article
Recenzirano
Odprti dostop
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 (Gamma < 1.4 at the 90% confidence level) suggestive of a reflection dominated continuum or an absorption turn-over suggestive of a column density higher than approx10 super(24) cm super(-2). We found a sample of nine heavily-obscured sources satisfying the above criteria. Four of these show statistically significant FeK alpha lines with large equivalent widths (three out of four have equivalent widths consistent with 1 keV) suggesting that these are the most certain Compton-thick AGN candidates. Two of these sources are transmission dominated while the other two are most probably reflection dominated Compton-thick AGN. Although this sample of four sources is by no means statistically complete, it represents the best example of Compton-thick sources found at moderate-to-high redshift with three sources at z = 1.2-1.5 and one source at z = 3.7. Using Spitzer and Herschel observations, we estimate with good accuracy the X-ray to mid-IR (12 mu m) luminosity ratio of our sources. These are well below the average AGN relation, independently suggesting that these four sources are heavily obscured.
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