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Context. The footprint of the recent second data release of the LOFAR Two-metre Sky Survey (LoTSS-DR2) covers 309 Planck Sunyaev-Zeldovich (SZ) selected galaxy clusters, 83 of which host a radio halo and 26 host a radio relic(s). It provides an excellent opportunity to statistically study the properties of extended cluster radio sources, especially their connection with merging activities. Aims. We quantify cluster dynamic states to investigate their relation with the occurrence of extended radio sources. We also search for connections between intracluster medium (ICM) turbulence and nonthermal characteristics of radio halos in the LoTSS-DR2. Methods. We analyzed XMM-Newton and Chandra archival X-ray data of all Planck SZ clusters in the footprint of LoTSS-DR2. We computed concentration parameters and centroid shifts that indicate the dynamic states of the clusters. We also performed a power spectral analysis of the X-ray surface brightness fluctuations to investigate large-scale density perturbations and estimate the turbulent velocity dispersion. Furthermore, we searched for the relation between radio halo power and the turbulent dissipation flux channeled to particle acceleration. Results. The concentration parameters measured by the two telescopes agree well, but the centroid shift has a larger scatter. The surface brightness power spectral analysis results in a large scatter of the surface brightness and density fluctuation amplitudes. We therefore only found a marginal anticorrelation between density fluctuations and cluster relaxation state, and we did not find a correlation between density fluctuations and radio halo power. Nevertheless, the injected power for particle acceleration calculated from turbulent dissipation is correlated with the radio halo power, where the best-fit unity slope supports the turbulent (re)acceleration scenario. Two different acceleration models, transit-time damping and adiabatic stochastic acceleration, cannot be distinguished due to the large scatter of the estimated turbulent Mach number. We introduced a new quantity [kBT YX]rRH, which is proportional to the turbulent acceleration power assuming a constant Mach number. This quantity is strongly correlated with radio halo power, where the slope is also unity. [ABSTRACT FROM AUTHOR]

We present an analysis of archival Chandra data of the merging galaxy cluster ClG 0217+70. The Fe XXV Heα X-ray emission line is clearly visible in the 25 ks observation, allowing a precise determination of the redshift of the cluster as z = 0.180 ± 0.006. We measure kT500 = 8.3  ±  0.4 keV and estimate M500 = (1.06 ± 0.11) × 1015 M⊙ based on existing scaling relations. Correcting both the radio and X-ray luminosities with the revised redshift reported here, which is much larger than previously inferred based on sparse optical data, this object is no longer an X-ray underluminous outlier in the LX − Pradio scaling relation. The new redshift also means that, in terms of physical scale, ClG 0217+70 hosts one of the largest radio halos and one of the largest radio relics known to date. Most of the relic candidates lie in projection beyond r200. The X-ray morphological parameters suggest that the intracluster medium is still dynamically disturbed. Two X-ray surface brightness discontinuities are confirmed in the northern and southern parts of the cluster, with density jumps of 1.40 ± 0.16 and 3.0 ± 0.6, respectively. We also find a 700 × 200 kpc X-ray faint channel in the western part of the cluster, which may correspond to compressed heated gas or increased non-thermal pressure due to turbulence or magnetic fields. [ABSTRACT FROM AUTHOR]

Context. Previous Chandra observations of the Abell 3411-3412 merging galaxy cluster system revealed an outbound bullet-like sub-cluster in the northern part and many surface brightness edges at the southern periphery, where multiple diffuse sources are also reported from radio observations. Notably, a southeastern radio relic associated with fossil plasma from a radio galaxy and with a detected X-ray edge provides direct evidence of shock re-acceleration. The properties of the reported surface brightness features have yet to be constrained from a thermodynamic viewpoint. Aims. We use the XMM-Newton and Suzaku observations of Abell 3411-3412 to reveal the thermodynamical nature of the previously reported re-acceleration site and other X-ray surface brightness edges. We also aim to investigate the temperature profile in the low-density outskirts with Suzaku data. Methods. We performed both imaging and spectral analysis to measure the density jump and the temperature jump across multiple known X-ray surface brightness discontinuities. We present a new method to calibrate the vignetting function and spectral model of the XMM-Newton soft proton background. Archival Chandra, Suzaku, and ROSAT data are used to estimate the cosmic X-ray background and Galactic foreground levels with improved accuracy compared to standard blank sky spectra. Results. At the southeastern edge, temperature jumps revealed by both XMM-Newton and Suzaku point to a ℳ ∼ 1.2 shock, which agrees with the previous result from surface brightness fits with Chandra. The low Mach number supports the re-acceleration scenario at this shock front. The southern edge shows a more complex scenario, where a shock and the presence of stripped cold material may coincide. There is no evidence for a bow shock in front of the northwestern "bullet" sub-cluster. The Suzaku temperature profiles in the southern low-density regions are marginally higher than the typical relaxed cluster temperature profile. The measured value kT500 = 4.84 ± 0.04 ± 0.19 keV with XMM-Newton and kT500 = 5.17 ± 0.07 ± 0.13 keV with Suzaku are significantly lower than previously inferred from Chandra. [ABSTRACT FROM AUTHOR]

We present XMM-Newton/EPIC observations of six merging galaxy clusters and study the distributions of their temperature, iron (Fe) abundance and pseudo-entropy along the merging axis. For the first time, we focused simultaneously, and in a comprehensive way, on the chemical and thermodynamic properties of the newly collided intra cluster medium (ICM). The Fe distribution of these clusters along the merging axis is found to be in good agreement with the azimuthally-averaged Fe abundance profile in typical non-cool-core clusters out to r500. In addition to showing a moderate central abundance peak, though less pronounced than in relaxed systems, the Fe abundance flattens at large radii towards ∼0.2−0.3 Z⊙. Although this shallow metal distribution is in line with the idea that disturbed, non-cool-core clusters originate from the merging of relaxed, cool-core clusters, we find that in some cases, remnants of metal-rich and low entropy cool cores can persist after major mergers. While we obtain a mild anti-correlation between the Fe abundance and the pseudo-entropy in the (lower entropy, K = 200−500 keV cm2) inner regions, no clear correlation is found at (higher entropy, K = 500−2300 keV cm2) outer radii. The apparent spatial abundance uniformity that we find at large radii is difficult to explain through an efficient mixing of freshly injected metals, particularly in systems for which the time since the merger is short. Instead, our results provide important additional evidence in favour of the early enrichment scenario in which the bulk of the metals are released outside galaxies at z >  2−3, and extend it from cool-core and (moderate) non-cool-core clusters to a few of the most disturbed merging clusters as well. These results constitute a first step toward a deeper understanding of the chemical history of merging clusters. [ABSTRACT FROM AUTHOR]

High-resolution spectroscopy of the core of the Perseus Cluster of galaxies, using the Hitomi satellite above 2 keV and the XMM–Newton Reflection Grating Spectrometer at lower energies, provides reliable constraints on the abundances of O, Ne, Mg, Si, S, Ar, Ca, Cr, Mn, Fe, and Ni. Accounting for all known systematic uncertainties, the Ar/Fe, Ca/Fe, and Ni/Fe ratios are determined with a remarkable precision of less than 10 per cent, while the constraints on Si/Fe, S/Fe, and Cr/Fe are at the 15 per cent level, and Mn/Fe is measured with a 20 per cent uncertainty. The average biases in determining the chemical composition using archival CCD spectra from XMM–Newton and Suzaku typically range from 15 to 40 per cent. A simple model in which the enrichment pattern in the Perseus Cluster core and the protosolar nebula are identical gives a surprisingly good description of the high-resolution X-ray spectroscopy results, with χ2 = 10.7 for 10 degrees of freedom. However, this pattern is challenging to reproduce with linear combinations of existing supernova nucleosynthesis calculations, particularly given the precise measurements of intermediate α-elements enabled by Hitomi. We discuss in detail the degeneracies between various supernova progenitor models and explosion mechanisms, and the remaining uncertainties in these theoretical models. We suggest that including neutrino physics in the core-collapse supernova yield calculations may improve the agreement with the observed pattern of α-elements in the Perseus Cluster core. Our results provide a complementary benchmark for testing future nucleosynthesis calculations required to understand the origin of chemical elements. [ABSTRACT FROM AUTHOR]

Aims. To understand the nature of transient obscuring outflows in active galactic nuclei, we use simultaneous multiwavelength observations with XMM-Newton, NuSTAR, the Hubble Space Telescope (HST), and the Max Planck Gesellschaft/European Southern Observatory (ESO) 2.2 m telescope triggered by soft X-ray absorption detected by Swift. Methods. We obtained ultraviolet spectra on 2016-12-12 and 2016-12-21 using the Cosmic Origins Spectrograph (COS) on HST simultaneously with X-ray spectra obtained with XMM-Newton and NuSTAR. We modeled the ultraviolet spectra to measure the strength and variability of the absorption, and used photoionization models to obtain its physical characteristics. Results. We find new components of broad, blue-shifted absorption associated with Lyα, N V, Si IV, and C IV in our COS spectra. The absorption extends from near-zero velocities in the rest-frame of the host galaxy to −6200 km s−1. These features appear for the first time in NGC 3783 at the same time as heavy soft X-ray absorption seen in the XMM-Newton X-ray spectra. The X-ray absorption has a column density of ∼1023 cm−2, and it partially covers the X-ray continuum source. Combining the X-ray column densities with the UV spectral observations yields an ionization parameter for the obscuring gas of log ξ = 1.84−0.2+0.4 erg cm s−1 log   ξ = 1. 84 − 0.2 + 0.4 erg   cm   s − 1 $ \log \xi = 1.84_{ - 0.2}^{ + 0.4}{\rm{erg}}\,{\rm{cm}}\,{{\rm{s}}^{ - 1}}\ $. Despite the high intensity of the UV continuum in NGC 3783, F(1470 Å) = 8 × 10−14 erg cm−2 s−1 Å−1>, the well known narrow UV absorption lines are deeper than in earlier observations in unobscured states, and low ionization states such as C III appear, indicating that the narrow-line gas is more distant from the nucleus and is being shadowed by the gas producing the obscuration. Despite the high continuum flux levels in our observations of NGC 3783, moderate velocities in the UV broad line profiles have substantially diminished. Conclusions.We suggest that a collapse of the broad line region has led to the outburst and triggered the obscuring event. [ABSTRACT FROM AUTHOR]

Our Swift monitoring program triggered two joint XMM-Newton, NuSTAR, and HST observations on 11 and 21 December 2016 targeting NGC 3783 because its soft X-ray continuum was heavily obscured. Consequently, emission features, including the O VII radiative recombination continuum, stand out above the diminished continuum. We focus on the photoionized emission features in the December 2016 Reflection Grating Spectrometer (RGS) spectra, and compare them to the time-averaged RGS spectrum obtained in 2000–2001 when the continuum was unobscured. A two-phase photoionized plasma is required to account for the narrow emission features. These narrow emission features are weakly varying between 2000–2001 and December 2016. We also find a statistically significant broad emission component in the time-averaged RGS spectrum in 2000–2001. This broad emission component is significantly weaker in December 2016, suggesting that the obscurer is farther away than the X-ray broad-line region. In addition, by analyzing the archival high-resolution X-ray spectra, we find that nine photoionized absorption components with different ionization parameters and kinematics are required for the warm absorber in X-rays. [ABSTRACT FROM AUTHOR]

The cosmological missing baryons at z <  1 most likely hide in the hot (T ≳ 105.5 K) phase of the warm hot intergalactic medium (WHIM). While the hot WHIM is hard to detect due to its high ionisation level, the warm (T ≲ 105.5 K) phase of the WHIM has been very robustly detected in the far-ultraviolet (FUV) band. We adopted the assumption that the hot and warm WHIM phases are co-located and therefore used the FUV-detected warm WHIM as a tracer for the cosmologically interesting hot WHIM. We performed an X-ray follow-up in the sight line of the blazar PKS 2155–304 at the redshifts where previous FUV measurements of O VI, Si IV, and broad Lyman-alpha (BLA) absorption have indicated the existence of the warm WHIM. We looked for the O VII Heα and O VIII Lyα absorption lines, the most likely hot WHIM tracers. Despite the very large exposure time (≈1 Ms), the Reflection Grating Spectrometer unit 1 (RGS1) on-board XMM-Newton data yielded no significant detection which corresponds to upper limits of log N(O VII(cm−2)) ≤ 14.5−15.2 and log N(O VIII(cm−2)) ≤ 14.5−15.2. An analysis of the data obtained with the combination of the Low Energy Transmission Grating (LETG) and the High Resolution Camera (HRC) on-board Chandra yielded consistent results. However, the data obtained with the LETG, combined with the Advanced CCD Imaging Spectrometer (ACIS) lead to the detection of an feature resembling an absorption line at λ ≈ 20 Å at simple one-parameter confidence level of 3.7σ, consistent with several earlier LETG/ACIS reports. Given the high statistical quality of the RGS1 data, the possibility of RGS1 accidentally missing the true line at λ ∼ 20 Å is very low: 0.006%. Neglecting this, the LETG/ACIS detection can be interpreted as Lyα transition of O VIII at one of the redshifts (z ≈ 0.054) of FUV-detected warm WHIM. Given the very convincing X-ray spectral evidence for and against the existence of the λ ∼ 20 Å feature, we cannot conclude whether or not it is a true astrophysical absorption line. Considering cosmological simulations, the probability of the LETG/ACIS λ ∼ 20 Å feature being due to the astrophysical O VIII absorber co-located with the FUV-detected O VI absorber is at the very low level of ≲0.1%. We cannot completely rule out the very unlikely possibility that the LETG/ACIS 20 Å feature is due to a transient event located close to the blazar. [ABSTRACT FROM AUTHOR]

The hot intracluster medium (ICM) pervading galaxy clusters and groups is rich in metals, which were synthesized by billions of supernovae and have accumulated in cluster gravitational wells for several gigayears. Since the products of both Type Ia and core-collapse supernovae – expected to explode over different time-scales – are found in the ICM, constraining accurately the chemical composition of these hot atmospheres can provide invaluable information on the history of the enrichment of large-scale structures. Recently, Hitomi observations reported solar abundance ratios in the core of the Perseus cluster, in tension with previous XMM–Newton measurements obtained for 44 cool-core clusters, groups, and massive ellipticals (the CHEERS sample). In this work, we revisit the CHEERS results by using an updated version of the spectral code used to fit the data (spexact v3), the same that was used to obtain the Hitomi measurements. Despite limitations in the spectral resolution, the average Cr/Fe and Ni/Fe ratios are now found to be remarkably consistent with unity and in excellent agreement with the Hitomi results. Our updated measurements suggest that the solar composition of the ICM of Perseus is a common feature in nearby cool-core systems. [ABSTRACT FROM AUTHOR]

We investigate the ionic column density variability of the ionized outflows associated with NGC∼7469, to estimate their location and power. This could allow a better understanding of galactic feedback of AGNs to their host galaxies. Analysis of seven XMM-Newton grating observations from 2015 is reported. We use an individual-ion spectral fitting approach, and compare different epochs to accurately determine variability on time-scales of years, months, and days. We find no significant column density variability in a 10 year period implying that the outflow is far from the ionizing source. The implied lower bound on the ionization equilibrium time, 10 years, constrains the lower limit on the distance to be at least 12 pc, and up to 31 pc, much less but consistent with the 1 kpc wide starburst ring. The ionization distribution of column density is reconstructed from measured column densities, nicely matching results of two 2004 observations, with one large high ionization parameter (ξ) component at 2

We present significantly improved measurements of turbulent velocities in the hot gaseous haloes of nearby giant elliptical galaxies. Using deep XMM-Newton Reflection Grating Spectrometer (RGS) observations and a combination of resonance scattering and direct line broadening methods, we obtain well bounded constraints for 13 galaxies. Assuming that the turbulence is isotropic, we obtain a best-fitting mean 1D turbulent velocity of ∼110 km s-1. This implies a typical 3D Mach number ∼0.45 and a typical non-thermal pressure contribution of∼6 per cent in the cores of nearby massive galaxies. The intrinsic scatter around these values is modest - consistent with zero, albeit with large statistical uncertainty - hinting at a common and quasi-continuous mechanism sourcing the velocity structure in these objects. Using conservative estimates of the spatial scales associated with the observed turbulent motions, we find that turbulent heating can be sufficient to offset radiative cooling in the inner regions of these galaxies (<10 kpc, typically 2-3 kpc). The full potential of our analysis methods will be enabled by future X-ray micro-calorimeter observations. [ABSTRACT FROM AUTHOR]

Context. Ionized outflows in active galactic nuclei (AGNs) are thought to influence their nuclear and local galactic environment. However, the distance of the outflows with respect to the central engine is poorly constrained, which limits our understanding of their kinetic power as a cosmic feedback channel. Therefore, the impact of AGN outflows on their host galaxies is uncertain. However, when the density of the outflows is known, their distance can be immediately obtained from their modeled ionization parameters. Aims. We perform a theoretical study of density diagnostics of ionized outflows using absorption lines from metastable levels in Be-like to C-like cosmic abundant ions. Methods. With the new self-consistent PhotoIONization (PION) model in the SPEX code, we are able to calculate detailed level populations, including the ground and metastable levels. This enables us to determine under what physical conditions the metastable levels are significantly populated. We then identify characteristic lines from these metastable levels in the 1-2000 Å wavelength range. Results. In the broad density range of nH ∈ (106, 1020) m-3, the metastable levels 2s2p (3P0−2) in Be-like ions can be significantly populated. For B-like ions, merely the first excited level 2s22p (2P3/2) can be used as a density probe. For C-like ions, the first two excited levels 2s22p2 ( 3P1 and 3P2) are better density probes than the next two excited levels 2s22p2 ( 1S0 and 1D2). Different ions in the same isoelectronic sequence cover not only a wide range of ionization parameters, but also a wide range of density values. On the other hand, within the same isonuclear sequence, those less ionized ions probe lower density and smaller ionization parameters. Finally, we reanalyzed the high-resolution grating spectra of NGC 5548 observed with Chandra in January 2002 using a set of PION components to account for the ionized outflow. We derive lower (or upper) limits of plasma density in five out of six PION components based on the presence (or absence) of the metastable absorption lines. Once atomic data from N-like to F-like ions are available, combined with the next generation of spectrometers that cover both X-ray and UV wavelength ranges with higher spectral resolution and larger effective areas, tight constraints on the density and thus the location and kinetic power of AGN outflows can be obtained. [ABSTRACT FROM AUTHOR]

Context. The chemical yields of supernovae and the metal enrichment of the intra-cluster medium (ICM) are not well understood. The hot gas in clusters of galaxies has been enriched with metals originating from billions of supernovae and provides a fair sample of large-scale metal enrichment in the Universe. High-resolution X-ray spectra of clusters of galaxies provide a unique way of measuring abundances in the hot intracluster medium (ICM). The abundance measurements can provide constraints on the supernova explosion mechanism and the initial-mass function of the stellar population. This paper introduces the CHEmical Enrichment RGS Sample (CHEERS), which is a sample of 44 bright local giant ellipticals, groups, and clusters of galaxies observed with XMM-Newton. Aims. The CHEERS project aims to provide the most accurate set of cluster abundances measured in X-rays using this sample. This paper focuses specifically on the abundance measurements of O and Fe using the reflection grating spectrometer (RGS) on board XMM-Newton. We aim to thoroughly discuss the cluster to cluster abundance variations and the robustness of the measurements. Methods. We have selected the CHEERS sample such that the oxygen abundance in each cluster is detected at a level of at least 5σ in the RGS. The dispersive nature of the RGS limits the sample to clusters with sharp surface brightness peaks. The deep exposures and the size of the sample allow us to quantify the intrinsic scatter and the systematic uncertainties in the abundances using spectral modeling techniques. Results. We report the oxygen and iron abundances as measured with RGS in the core regions of all 44 clusters in the sample. We do not find a significant trend of O/Fe as a function of cluster temperature, but we do find an intrinsic scatter in the O and Fe abundances from cluster to cluster. The level of systematic uncertainties in the O/Fe ratio is estimated to be around 20−30%, while the systematic uncertainties in the absolute O and Fe abundances can be as high as 50% in extreme cases. Thanks to the high statistics of the observations, we were able to identify and correct a systematic bias in the oxygen abundance determination that was due to an inaccuracy in the spectral model. Conclusions. The lack of dependence of O/Fe on temperature suggests that the enrichment of the ICM does not depend on cluster mass and that most of the enrichment likely took place before the ICM was formed. We find that the observed scatter in the O/Fe ratio is due to a combination of intrinsic scatter in the source and systematic uncertainties in the spectral fitting, which we are unable to separate. The astrophysical source of intrinsic scatter could be due to differences in active galactic nucleus activity and ongoing star formation in the brightest cluster galaxy. The systematic scatter is due to uncertainties in the spatial line broadening, absorption column, multi-temperature structure, and the thermal plasma models. [ABSTRACT FROM AUTHOR]

Context. It has been shown that for the analysis of X-ray spectra the C-statistic, contrary to the χ2-statistic, provides unbiased estimates of the model parameters and their uncertainty ranges. Aims. However, it is often stated that the C-statistic cannot be used to carry out statistical tests on the goodness of fit of the model, and therefore several investigations are still based on χ2-statistics. Methods. Here we show that it is straightforward to calculate the expected value and variance of the C-statistic so that it can be used in tests. Results. We provide formulae and simple numerical approximations to evaluate these expected values and variances. We also give examples indicating that tests based on only the expected value and variance of the C-statistic are reliable for spectra even with only ~30 counts. Conclusions. The C-statistic can be used for statistical tests such as assessing the goodness of fit of a spectral model. [ABSTRACT FROM AUTHOR]

Far-ultraviolet (FUV) observations have revealed transition temperature gas (TTG; log T(K)~ 5), located in the lower Galactic halo and in high-velocity clouds. However, the corresponding X-ray absorption has so far remained mostly undetected. In order to make an improvement in this respect in Galactic X-ray absorption studies, we accumulated very deep (~3 Ms) spectra of the blazar PKS 2155-304 obtained with the spectrometers RGS1, RGS2, LETG/HRC, and LETG/ACIS-S and studied the absorption lines due to the intervening Galactic components. The very high quality of the data and coverage of important wavelengths with at least two independent instruments allowed us to reliably detect 10 Galactic lines with better than 99.75% confidence. We discovered significant absorption from blended O iv transitions 1s-2p 2S (22.571 Å), 1s-2p 2P (22.741 Å), and 1s-2p 2D (22.777 Å), and from the O v transition 1s-2p (22.370 Å) from TTG at log T(K)=5.2 ± 0.1. A joint X-ray and FUV analysis indicated that photoionisation is negligible for this component and that the gas is in a cooling transition phase. However, the temperature is high enough that the column density ratio N(O iv)/N(O v) is not significantly different from that in collisional ionisation equilibrium (CIE). Under CIE we obtained NOIV = 3.6 ± 2.0 ×1015 cm-2, corresponding to NH = 1.0 ± 0.5 ×1019(Z☉/ZTTG) cm-2. [ABSTRACT FROM AUTHOR]

The hot intra-cluster medium (ICM) permeating galaxy clusters and groups is not pristine, as it has been continuously enriched by metals synthesised in Type Ia (SNIa) and core-collapse (SNcc) supernovae since the major epoch of star formation (z ≃ 2–3). The cluster/group enrichment history and mechanisms responsible for releasing and mixing the metals can be probed via the radial distribution of SNIa and SNcc products within the ICM. In this paper, we use deep XMM-Newton/EPIC observations from a sample of 44 nearby cool-core galaxy clusters, groups, and ellipticals (CHEERS) to constrain the average radial O, Mg, Si, S, Ar, Ca, Fe, and Ni abundance profiles. The radial distributions of all these elements, averaged over a large sample for the first time, represent the best constrained profiles available currently. Specific attention is devoted to a proper modelling of the EPIC spectral components, and to other systematic uncertainties that may affect our results. We find an overall decrease of the Fe abundance with radius out to ~0.9 r500 and ~0.6 r500 for clusters and groups, respectively, in good agreement with predictions from the most recent hydrodynamical simulations. The average radial profiles of all the other elements (X) are also centrally peaked and, when rescaled to their average central X/Fe ratios, follow well the Fe profile out to at least ~0.5 r500. As predicted by recent simulations, we find that the relative contribution of SNIa (SNcc) to the total ICM enrichment is consistent with being uniform at all radii, both for clusters and groups using two sets of SNIa and SNcc yield models that reproduce the X/Fe abundance pattern in the core well. In addition to implying that the central metal peak is balanced between SNIa and SNcc, our results suggest that the enriching SNIa and SNcc products must share the same origin and that the delay between the bulk of the SNIa and SNcc explosions must be shorter than the timescale necessary to diffuse out the metals. Finally, we report an apparent abundance drop in the very core of 14 systems (~32% of the sample). Possible origins of these drops are discussed. [ABSTRACT FROM AUTHOR]

Every observation of astrophysical objects involving a spectrum requires atomic data for the interpretation of line fluxes, line ratios, and ionization state of the emitting plasma. One of the processes that determines it is collisional ionization. In this study, an update of the direct ionization (DI) and excitation-autoionization (EA) processes is discussed for the H to Zn-like isoelectronic sequences. In recent years, new laboratory measurements and theoretical calculations of ionization cross-sections have become available. We provide an extension and update of previous published reviews in the literature. We include the most recent experimental measurements and fit the cross-sections of all individual shells of all ions from H to Zn. These data are described using an extension of Younger's and Mewe's formula, suitable for integration over a Maxwellian velocity distribution to derive the subshell ionization rate coefficients. These ionization rate coefficients are incorporated in the high-resolution plasma code and spectral fitting tool SPEX V3.0. [ABSTRACT FROM AUTHOR]

We present the results of deep 140 ks Suzaku X-ray observations of the north-east (NE) radio relic of the merging galaxy cluster Abell 2255. The temperature structure of Abell 2255 is measured out to 0.9 times the virial radius (1.9 Mpc) in the NE direction for the first time. The Suzaku temperature map of the central region suggests a complex temperature distribution, which agrees with previous work. Additionally, on a larger-scale, we confirm that the temperature drops from 6 keV around the cluster center to 3 keV at the outskirts, with two discontinuities at r ~ 50' (450 kpc) and ~12' (1100 kpc) from the cluster center. Their locations coincide with surface brightness discontinuities marginally detected in the XMM-Newton image, which indicates the presence of shock structures. From the temperature drop, we estimate the Mach numbers to be Minner ~ 1:2 and, Mouter ~ 1:4. The first structure is most likely related to the large cluster core region (~350-430 kpc), and its Mach number is consistent with the XMM-Newton observation (M ~ 1:24: Sakelliou & Ponman 2006, MNRAS, 367, 1409). Our detection of the second temperature jump, based on the Suzaku key project observation, shows the presence of a shock structure across the NE radio relic. This indicates a connection between the shock structure and the relativistic electrons that generate radio emission. Across the NE radio relic, however, we find a significantly lower temperature ratio (T1=T2 ~ 1:44±0:16 corresponds to MX-ray ~ 1:4) than the value expected from radio wavelengths, based on the standard diffusive shock acceleration mechanism (T1=T2 > 3:2 orMRadio > 2:8). This may suggest that under some conditions, in particular the NE relic of A2255 case, the simple diffusive shock acceleration mechanism is unlikely to be valid, and therefore, more a sophisticated mechanism is required. [ABSTRACT FROM AUTHOR]

Since the launch of Chandra and XMM-Newton, high-resolution X-ray spectra of cosmic sources of all kinds have become available. These spectra have resulted in major scientific breakthroughs. However, because of the techniques used, in general, high-quality spectra can be obtained only for the brightest few sources of each class. Moreover, except for the most compact extended sources, such as cool core clusters, grating spectra are limited to point sources. Hitomi made another major step forward, providing for the first time a high-quality spectrum of an extended source and improved spectral sensitivity in the Fe-K band. For point sources with the proposed Arcus mission, and for all sources with the launch of Athena, X-ray spectroscopy will become mature. It will allow us to extend the investigations from the few handful of brightest sources of each category to a large number of sources far away in space and time, or to get high time resolution and high spectral resolution spectra of bright time-variable sources. [ABSTRACT FROM AUTHOR]

The hot intra-cluster medium (ICM) is rich in metals, which are synthesised by supernovae (SNe) explosions and accumulate over time into the deep gravitational potential well of clusters of galaxies. Since most of the elements visible in X-rays are formed by type Ia (SNIa) and/or core-collapse (SNcc) supernovae, measuring their abundances gives us direct information on the nucleosynthesis products of billions of SNe since the epoch of the star formation peak (z ∼ 2−3). In this study, we use the EPIC and RGS instruments on board XMM-Newton to measure the abundances of nine elements (O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni) from a sample of 44 nearby cool-core galaxy clusters, groups, and elliptical galaxies. We find that the Fe abundance shows a large scatter (∼20-40%) over the sample, within 0.2r500 and especially 0.05r500. Unlike the absolute Fe abundance, the abundance ratios (X/Fe) are uniform over the considered temperature range (∼0.6-8 keV) and with a limited scatter. In addition to an unprecedented treatment of systematic uncertainties, we provide the most accurate abundance ratios measured so far in the ICM, including Cr/Fe and Mn/Fe which we firmly detected (>4σ with MOS and pn independently). We find that Cr/Fe, Mn/Fe, and Ni/Fe differ significantly from the proto-solar values. However, the large uncertainties in the proto-solar abundances prevent us from making a robust comparison between the local and the intra-cluster chemical enrichments. We also note that, interestingly, and despite the large net exposure time (∼4.5 Ms) of our dataset, no line emission feature is seen around ∼3.5 keV. [ABSTRACT FROM AUTHOR]

He-like ions produce distinctive series of triplet lines under various astrophysical conditions. However, this emission can be affected by line absorption from Li-like ions in the same medium.We investigate this absorption of He-like triplets and present the implications for diagnostics of plasmas in photoionisation equilibrium using the line ratios of the triplets. Our computations were carried out for the OVI and Fe XXIV absorption of the OVII and Fe XXV triplet emission lines, respectively. The fluorescent emission by the Li-like ions and continuum absorption of the He-like ion triplet lines are also investigated. We determine the absorption of the triplet lines as a function of Li-like ion column density and velocity dispersion of the emitting and absorbing medium. We find O VI line absorption can significantly alter the O VII triplet line ratios in optically-thin plasmas, by primarily absorbing the intercombination lines, and to a lesser extent, the forbidden line. Because of intrinsic line absorption by O VI inside a photoionised plasma, the predicted ratio of forbidden to intercombination line intensity for the O VII triplet increases from 4 up to an upper limit of 16. This process can explain the triplet line ratios that are higher than expected and that are seen in some X-ray observations of photoionised plasmas. For the Fe XXV triplet, line absorption by Fe XXIV becomes less apparent owing to significant fluorescent emission by Fe XXIV. Without taking the associated Li-like ion line absorption into account, the density diagnosis of photoionised plasmas using the observed line ratios of the He-like ion triplet emission lines can be unreliable, especially for low-Z ions. [ABSTRACT FROM AUTHOR]

During an extensive multiwavelength campaign that we performed in 2013-2014, we found the prototypical Seyfert 1 galaxy NGC 5548 in an unusual condition of heavy and persistent obscuration. The newly discovered "obscurer" absorbs most of the soft X-ray continuum along our line of sight and lowers the ionizing luminosity received by the classical warm absorber. We present the analysis of the high resolution X-ray spectra collected with XMM-Newton and Chandra throughout the campaign, which are suitable to investigate the variability of both the obscurer and classical warm absorber. The time separation between these X-ray observations range from two days to eight months. On these timescales the obscurer is variable both in column density and in covering fraction. This is consistent with the picture of a patchy wind. The most significant variation occurred in September 2013 when the source brightened for two weeks. A higher and steeper intrinsic continuum and a lower obscurer covering fraction are both required to explain the spectral shape during the flare.We suggest that a geometrical change of the soft X-ray source behind the obscurer causes the observed drop in the covering fraction. Because of the higher soft X-ray continuum level, the September 2013 Chandra spectrum is the only X ray spectrum of the campaign in which individual features of the warm absorber could be detected. The spectrum shows absorption from Fe-UTA, Oiv, and Ov, consistent with belonging to the lower-ionization counterpart of the historical NGC 5548 warm absorber. Hence, we confirm that the warm absorber has responded to the drop in the ionizing luminosity caused by the obscurer. [ABSTRACT FROM AUTHOR]

Recent progress in numerical simulations of thermonuclear supernova explosions brings up a unique opportunity in studying the progenitors of Type Ia supernovae. Coupling state-of-the-art explosion models with detailed hydrodynamical simulations of the supernova remnant evolution and the most up-to-date atomic data for X-ray emission calculations makes it possible to create realistic synthetic X-ray spectra for the supernova remnant phase. Comparing such spectra with high-quality observations of supernova remnants could allow us to constrain the explosion mechanism and the progenitor of the supernova. The present study focuses in particular on the oxygen emission line properties in young supernova remnants, since different explosion scenarios predict a different amount and distribution of this element. Analysis of the soft X-ray spectra from supernova remnants in the Large Magellanic Cloud and confrontation with remnant models for different explosion scenarios suggest that SNR 0509-67.5 could originate from a delayed detonation explosion and SNR 0519-69.0 from an oxygen-rich merger. [ABSTRACT FROM AUTHOR]

Clusters of galaxies are the largest gravitationally bounded structures in the Universe dominated by dark matter. We review the observational appearance and physical models of plasma structures in clusters of galaxies. Bubbles of relativistic plasma which are inflated by supermassive black holes of AGNs, cooling and heating of the gas, large scale plasma shocks, cold fronts, non-thermal halos and relics are observed in clusters. These constituents are reflecting both the formation history and the dynamical properties of clusters of galaxies. We discuss X-ray spectroscopy as a tool to study the metal enrichment in clusters and fine spectroscopy of Fe X-ray lines as a powerful diagnostics of both the turbulent plasma motions and the energetics of the non-thermal electron populations. The knowledge of the complex dynamical and feedback processes is necessary to understand the energy and matter balance as well as to constrain the role of the non-thermal components of clusters. [ABSTRACT FROM AUTHOR]

We describe the analysis of the seven broad-band X-ray continuum observations of the archetypal Seyfert 1 galaxy NGC 5548 that were obtained with XMM-Newton or Chandra, simultaneously with high-energy (>10 keV) observations with NuSTAR and INTEGRAL. These data were obtained as part of a multiwavelength campaign undertaken from the summer of 2013 till early 2014. We find evidence of a high-energy cut-o in at least one observation, which we attribute to thermal Comptonization, and a constant reflected component that is likely due to neutral material at least a few light months away from the continuum source. We confirm the presence of strong, partial covering X-ray absorption as the explanation for the sharp decrease in flux through the soft X-ray band. The obscurers appear to be variable in column density and covering fraction on time scales as short as weeks. A fit of the average spectrum over the range 0.3-400 keV with a realistic Comptonization model indicates the presence of a hot corona with a temperature of 40+40 -10 keV and an optical depth of 2:7-1:2+0:7 if a spherical geometry is assumed. [ABSTRACT FROM AUTHOR]

Context. AGN outflows are thought to influence the evolution of their host galaxies and of super massive black holes. Our deep multiwavelength campaign on NGC 5548 has revealed a new, unusually strong X-ray obscuration, accompanied by broad UV absorption troughs observed for the first time in this object. The X-ray obscuration caused a dramatic decrease in the incident ionizing flux on the outflow that produces the long-studied narrow UV absorption lines in this AGN. The resulting data allowed us to construct a comprehensive physical, spatial, and temporal picture for this enduring AGN wind. Aims. We aim to determine the distance of the narrow UV outflow components from the central source, their total column-density, and the mechanism responsible for their observed absorption variability. Methods. We study the UV spectra acquired during the campaign, as well as from four previous epochs (1998-2011). Our main analysis tools are ionic column-density extraction techniques, photoionization models based on the code CLOUDY, and collisional excitation simulations. Results. A simple model based on a fixed total column-density absorber, reacting to changes in ionizing illumination, matches the very different ionization states seen in five spectroscopic epochs spanning 16 years. The main component of the enduring outflow is situated at 3.5 ± 1.1 pc from the central source, and its distance and number density are similar to those of the narrow-emitting-line region in this object. Three other components are situated between 5-70 pc and two are farther than 100 pc. The wealth of observational constraints and the anti-correlation between the observed X-ray and UV flux in the 2002 and 2013 epochs make our physical model a leading contender for interpreting trough variability data of quasar outflows. Conclusions. This campaign, in combination with prior UV and X-ray data, yields the first simple model that can explain the physical characteristics and the substantial variability observed in an AGN outflow. [ABSTRACT FROM AUTHOR]

Using the EPIC and RGS data from a deep (200 ks) XMM-Newton observation, we investigate the temperature structure (kT and σT) and the abundances of nine elements (O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni) of the intra-cluster medium (ICM) in the nearby (z = 0:046) cool-core galaxy cluster Abell 4059. Next to a deep analysis of the cluster core, a careful modelling of the EPIC background allows us to build radial profiles up to 12' (~650 kpc) from the core. Probably because of projection effects, the temperature ICM is not found to be in single phase, even in the outer parts of the cluster. The abundances of Ne, Si, S, Ar, Ca, and Fe, but also O are peaked towards the core. The elements Fe and O are still significantly detected in the outermost annuli, which suggests that the enrichment by both type Ia and core-collapse SNe started in the early stages of the cluster formation. However, the particularly high Ca/Fe ratio that we find in the core is not well reproduced by the standard SNe yield models. Finally, 2D maps of temperature and Fe abundance are presented and confirm the existence of a denser, colder, and Fe-rich ridge south-west of the core, previously observed by Chandra. The origin of this asymmetry in the hot gas of the cluster core is still unclear, but it might be explained by a past intense ram-pressure stripping event near the central cD galaxy. [ABSTRACT FROM AUTHOR]

Context. XMM-Newton was launched on 10 December 1999 and has been operational since early 2000. One of the instruments onboard XMM-Newton is the reflection grating spectrometer (RGS). Two identical RGS instruments are available, with each RGS combining a reflection grating assembly and a camera with charge-coupled devices to record the spectra. Aims. We describe the calibration and in-orbit performance of the RGS instrument. By combining the preflight calibration with appropriate inflight calibration data including the changes in detector performance over time, we aim at profound knowledge about the accuracy in the calibration. This will be crucial for any correct scientific interpretation of spectral features for a wide variety of objects. Methods. Ground calibrations alone are not able to fully characterize the instrument. Dedicated inflight measurements and constant monitoring are essential for a full understanding of the instrument and the variations of the instrument response over time. Physical models of the instrument are tuned to agree with calibration measurements and are the basis from which the actual instrument response can be interpolated over the full parameter space. Results. Uncertainties in the instrument response have been reduced to <10% for the effective area and <6 mÅ for the wavelength scale (in the range from 8 Å to 34 Å). The remaining systematic uncertainty in the detection of weak absorption features has been estimated to be 1.5%. Conclusions. Based on a large set of inflight calibration data and comparison with other instruments onboard XMM-Newton, the calibration accuracy of the RGS instrument has been improved considerably over the preflight calibrations. [ABSTRACT FROM AUTHOR]

Active galactic nuclei (AGN) are the most luminous persistent objects in the universe. The X-ray domain is particularly important because the X-ray flux represents a significant fraction of the bolometric emission from such objects and probes the innermost regions of accretion disks, where most of this power is generated. An excess of X-ray emission below ~2 keV, called soft-excess, is very common in Type 1 AGN spectra. The origin of this feature remains debated. Originally modeled with a blackbody, there are now several possibilities to model the soft-excess, including warm Comptonization and blurred ionized reflection. In this paper, we test ionized-reflection models on Mrk 509, a bright Seyfert 1 galaxy for which we have a unique data set, in order to determine whether it can be responsible for the strong soft-excess. We use ten simultaneous XMM-Newton and INTEGRAL observations performed every four days. We present here the results of the spectral analysis, the evolution of the parameters, and the variability properties of the X-ray emission. The application of blurred ionized-reflection models leads to a very strong reflection and an extreme geometry, but fails to reproduce the broad-band spectrum of Mrk 509. Two different scenarios for blurred ionized reflection are discussed: stable geometry and lamp-post configuration. In both cases we find that the model parameters do not follow the expected relations, indicating that the model is fine-tuned to fit the data without physical justification. A large, slow variation in the soft-excess without a counterpart in the hard X-rays could be explained by a change in ionization of the reflector. However, such a change does not naturally follow from the assumed geometrical configuration. Warm Comptonization remains the most probable origin of the soft-excess in this object. Nevertheless, it is possible that both ionized reflection and warm Comptonization mechanisms can explain the soft-excess in all objects, one dominating the other one, depending on the physical conditions of the disk and the corona. [ABSTRACT FROM AUTHOR]

We have developed a new method to approach the missing baryons problem. We assume that the missing baryons reside in a form of Warm Hot Intergalactic Medium, i.e. the WHIM. Our method consists of (a) detecting the coherent large scale structure in the spatial distribution of galaxies that traces the Cosmic Web and that in hydrodynamical simulations is associated to the WHIM, (b) mapping its luminosity into a galaxy luminosity density field, (c) using numerical simulations to relate the luminosity density to the density of the WHIM, (d) applying this relation to real data to trace the WHIM using the observed galaxy luminosities in the Sloan Digital Sky Survey and 2dF redshift surveys. In our application we find evidence for the WHIM along the line of sight to the Sculptor Wall, at redshifts consistent with the recently reported X-ray absorption line detections. Our indirect WHIM detection technique complements the standard method based on the detection of characteristic X-ray absorption lines, showing that the galaxy luminosity density is a reliable signpost for the WHIM. For this reason, our method could be applied to current galaxy surveys to optimise the observational strategies for detecting and studying the WHIM and its properties. Our estimates of the WHIM hydrogen column density NH in Sculptor agree with those obtained via the X-ray analysis. Due to the additional NH estimate, our method has potential for improving the constrains of the physical parameters of the WHIM as derived with X-ray absorption, and thus for improving the understanding of the missing baryons problem. [ABSTRACT FROM PUBLISHER]

Context. Low-mass X-ray binaries (LMXBs) are a natural workbench to study accretion disk phenomena and optimal background sources to measure elemental abundances in the interstellar medium (ISM). In high-resolution XMM-Newton spectra, the LMXB SAX J1808.4-3658 in the past showed a neon column density significantly higher than expected given its small distance, presumably due to additional absorption from a neon-rich circumstellar medium (CSM). Aims. It is possible to detect intrinsic absorption from the CSM by evidence of Keplerian motions or outflows. For this purpose, we analyze a recent, deep (100 ks long), high-resolution Chandra/LETGS spectrum of SAX J1808.4-3658 in combination with archival data. Methods. We estimated the column densities of the different absorbers through the study of their absorption lines. We used both empirical and physical models involving photo- and collisional-ionization to determine the nature of the absorbers. Results. The abundances of the cold interstellar gas match the solar values as expected given the proximity of the X-ray source. For the first time in this source, we detected neon and oxygen blueshifted absorption lines, which can be well modeled with outflowing photoionized gas. The wind is neon rich (Ne/O≲ 3) and may originate from processed, ionized gas near the accretion disk or its corona. The kinematics (v = 500-1000 km s-1) are indeed similar to those seen in other accretion disks. We also discovered a system of emission lines with very high Doppler velocities (v ~ 24 000 km s-1) originating presumably closer to the compact object. Additional observations and UV coverage are needed to accurately determine the abundances and the ionization structure of the wind. [ABSTRACT FROM AUTHOR]

In this paper, we present the longest exposed (97 ks) XMM-Newton EPIC-pn spectrum ever obtained for the Seyfert 1.5 galaxy 1H 0419-577. With the aim of explaining the broadband emission of this source, we took advantage of the simultaneous coverage in the optical/UV that was provided in the present case by the XMM-Newton Optical Monitor and by a HST-COS observation. Archival FUSE flux measurements in the far-ultraviolet were also used for the present analysis. We successfully modeled the X-ray spectrum and the optical/UV fluxes data points using a Comptonization model. We found that a blackbody temperature of T ~ 56 eV accounts for the optical/UV emission originating in the accretion disk. This temperature serves as an input for the Comptonized components that model the X-ray continuum. Both a warm (Twc ~ 0.7 keV, Twc ~ 7) and a hot corona (Thc ~ 160 keV, Thc ~ 0.5) intervene to upscatter the disk photons to X-ray wavelengths. With the addition of a partially covering (Cv ~ 50%) cold absorber with a variable opacity ( NH ~ [1019-1022] cm-2), this model can also explain the historical spectral variability of this source, with the present dataset presenting the lowest one ( NH ~ 1019 cm-2). We discuss a scenario where the variable absorber becomes less opaque in the highest flux states because it gets ionized in response to the variations of the X-ray continuum. The lower limit for the absorber density derived in this scenario is typical for the broad line region clouds. We infer that 1H 0419-577 may be viewed from an intermediate inclination angle i ⩾ 54°, and, on this basis, we speculate that the X-ray obscuration may be associated with the innermost dust-free region of the obscuring torus. Finally, we critically compare this scenario with all the different models (e.g., disk reflection) that have been used in the past to explain the variability of this source. [ABSTRACT FROM AUTHOR]