X-ray spectra of the Fe-L complex Gu, L.; Shah, C.; Mao, J. ...
Astronomy and astrophysics (Berlin),
08/2022, Letnik:
664
Journal Article
Recenzirano
Odprti dostop
There has been a growing request from the X-ray astronomy community for a quantitative estimate of systematic uncertainties originating from the atomic data used in plasma codes. Though there have ...been several studies looking into atomic data uncertainties using theoretical calculations, in general, there is no commonly accepted solution for this task. We present a new approach for estimating uncertainties in the line emissivities for the current models of collisional plasma, mainly based upon a dedicated analysis of observed high resolution spectra of stellar coronae and galaxy clusters. We find that the systematic uncertainties of the observed lines consistently show an anticorrelation with the model line fluxes, after properly accounting for the additional uncertainties from the ion concentration calculation. The strong lines in the spectra are in general better reproduced, indicating that the atomic data and modeling of the main transitions are more accurate than those for the minor ones. This underlying anticorrelation is found to be roughly independent of source properties, line positions, ion species, and the line formation processes. We further applied our method to the simulated XRISM and Athena observations of collisional plasma sources and discuss the impact of uncertainties on the interpretation of these spectra. The typical uncertainties are 1–2% on temperature and 3–20% on abundances of O, Ne, Fe, Mg, and Ni.
An XMM-Newton view of the M 17 nebula Mernier, F.; Rauw, G.
New astronomy,
April 2013, 2013-4-00, 2013-04-01, Letnik:
20
Journal Article, Web Resource
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► We present the analysis of an XMM observation of the M17 nebula. ► The two X-ray brighets O-stars display hard spectra (kT of 3.8 and 2.6keV) indicating a colliding wind origin. ► The strong ...interstellar reddening towards the O-type stars leads to huge uncertainties on their Lx/Lbol values. ► Low-mass pre-main sequence stars exhibit considerable long term (months to years) variability. ► There is little correspondence between UV and X-ray sources in the M17 field of view.
We present the analysis of an XMM-Newton observation of the M 17 nebula. The X-ray point source population consists of massive O-type stars and a population of probable low-mass pre-main sequence stars. CEN 1a,b and OI 352, the X-ray brightest O-type stars in M 17, display hard spectra (kT of 3.8 and 2.6keV) consistent with a colliding wind origin in binary/multiple systems. We show that the strong interstellar reddening towards the O-type stars of M 17 yields huge uncertainties on their LX/Lbol values. The low-mass pre-main sequence stars exhibit hard spectra resulting from a combination of high plasma temperatures and very large interstellar absorption. We find evidence for considerable long term (months to years) variability of these sources. M 17 is one of the few star formation complexes in our Galaxy producing diffuse X-ray emission. We analyze the spectrum of this emission and compare it with previous studies. Finally, we discuss the Optical Monitor UV data obtained simultaneously with the X-ray images. We find very little correspondence between the UV and X-ray sources, indicating that the majority of the UV sources are foreground stars, whilst the bulk of the X-ray sources are deeply embedded in the M 17 complex.
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.
The hot intra-cluster medium (ICM) is rich in metals, which are synthesised by supernovae (SNe) 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 compare the most accurate average X/Fe abundance ratios (compiled in a previous work from XMM-Newton EPIC and RGS observations of 44 galaxy clusters, groups, and ellipticals), representative of the chemical enrichment in the nearby ICM, to various SNIa and SNcc nucleosynthesis models found in the literature. The use of a SNcc model combined to any favoured standard SNIa model (deflagration or delayed-detonation) fails to reproduce our abundance pattern. In particular, the Ca/Fe and Ni/Fe ratios are significantly underestimated by the models. We show that the Ca/Fe ratio can be reproduced better, either by taking a SNIa delayed-detonation model that matches the observations of the Tycho supernova remnant, or by adding a contribution from the “Ca-rich gap transient” SNe, whose material should easily mix into the hot ICM. On the other hand, the Ni/Fe ratio can be reproduced better by assuming that both deflagration and delayed-detonation SNIa contribute in similar proportions to the ICM enrichment. In either case, the fraction of SNIa over the total number of SNe (SNIa+SNcc) contributing to the ICM enrichment ranges within 29–45%. This fraction is found to be systematically higher than the corresponding SNIa/(SNIa+SNcc) fraction contributing to the enrichment of the proto-solar environnement (15–25%). We also discuss and quantify two useful constraints on both SNIa (i.e. the initial metallicity on SNIa progenitors and the fraction of low-mass stars that result in SNIa) and SNcc (i.e. the effect of the IMF and the possible contribution of pair-instability SNe to the enrichment) that can be inferred from the ICM abundance ratios. Finally, we show that detonative sub-Chandrasekhar WD explosions (resulting, for example, from violent WD mergers) cannot be a dominant channel for SNIa progenitors in galaxy clusters.
B
2O
3 interacts with hydroxide melts and yields water and a mixture of BO
3−
3 and BO
5−
4 ions. In this work, the ratio of the concentrations of these two ionic species has been determined at 623 K ...as a function of the composition of mixtures of sodium and potassium hydroxides in a range extending from 24 to 100 mol% NaOH. The ratio C(BO
5−
4)/C(BO
3−
3) has a maximum value for the 24 mol% NaOH mixture and a minimum value for the 50 mol% mixture. This composition dependence of the stoichiometry of the dissolved boron species was interpreted in relation to changes of the acidobasic properties of hydroxide melts.}
We present a robust representation of the chemical and thermal structure in the galaxy group NGC 5813 using archival, deep X-ray observations, and employing a multi-temperature spectral model based ...on up to date atomic line emission databases. The selection of our target is motivated by the fact that NGC 5813 has a very relaxed morphology, making it a promising candidate for the study of the AGN feedback's influence in the intra-group medium (IGrM). Our results showcase a prominent, extended distribution of cool gas along the group's NE-SW direction, correlating with the direction along which the supermassive black hole in the group's central galaxy is known to interact with the IGrM. Our analysis indicates gas being uplifted from the group's centre as the probable origin of the cool gas, although alternative scenarios, such as in-situ cooling can not be explicitly ruled out. Regarding the chemical structure of the IGrM, and unlike previous findings in massive clusters, we find no evidence for recent metal transport by jets/lobes from the central AGN. Instead, elemental abundances remain near Solar on average across the group. The distribution of elements appears to be independent of galactocentric radius, azimuth and the thermodynamics of the gas, suggesting that the IGrM has been efficiently mixed. The large scale uniformity of the abundance distribution implies the presence of complex dynamical processes in NGC 5813, despite its overall relaxed morphology. Past events of extreme AGN feedback or sloshing could be the primary mechanisms behind this.
We present azimuthally averaged metal abundance profiles from a full, comprehensive, and conservative re-analysis of the deep (\(\sim\)800 ks total net exposure) \textit{Chandra}/ACIS-S observation ...of the Centaurus cluster core (NGC\,4696). After carefully checking various sources of systematic uncertainties, including the choice of the spectral deprojection method, assumptions about the temperature structure of the gas, and uncertainties in the continuum modeling, we confirm the existence of a central drop in the abundances of the `reactive' elements Fe, Si, S, Mg, and Ca, within \(r\lesssim\)10 kpc. The same drops are also found when analyzing the \textit{XMM-Newton}/EPIC data (\(\sim\)150 ks). Adopting our most conservative approach, we find that, unlike the central drops seen for Fe, Si, S, Mg and Ca, the abundance of the `nonreactive' element Ar is fully consistent with showing no central drop. This is further confirmed by the significant (\(>3\sigma\)) central radial increase of the Ar/Fe ratio. Our results corroborate the previously proposed `dust depletion scenario' , in which central metal abundance drops are explained by the deposition of a significant fraction of centrally cooled reactive metals into dust grains present in the central regions of the Centaurus cluster. This is also supported by the previous findings that the extent of the metal abundance drops in NGC\,4696 broadly coincides with the infrared dust emission.
The distribution of chemical elements in the hot intracluster medium (ICM) retains valuable information about the enrichment and star formation histories of galaxy clusters, and on the feedback and ...dynamical processes driving the evolution of the cosmic baryons. In the present study we review the progresses made so far in the modelling of the ICM chemical enrichment in a cosmological context, focusing in particular on cosmological hydrodynamical simulations. We will review the key aspects of embedding chemical evolution models into hydrodynamical simulations, with special attention to the crucial assumptions on the initial stellar mass function, stellar lifetimes and metal yields, and to the numerical limitations of the modelling. At a second stage, we will overview the main simulation results obtained in the last decades and compare them to X-ray observations of the ICM enrichment patterns. In particular, we will discuss how state-of-the-art simulations are able to reproduce the observed radial distribution of metals in the ICM, from the core to the outskirts, the chemical diversity depending on cluster thermo-dynamical properties, the evolution of ICM metallicity and its dependency on the system mass from group to cluster scales. Finally, we will discuss the limitations still present in modern cosmological, chemical, hydrodynamical simulations and the perspectives for improving the theoretical modelling of the ICM enrichment in galaxy clusters in the future.
The CHEERS (CHEmical Enrichment RGS Sample) observations of clusters of galaxies with XMM-Newton have shown to be valuable to constrain the chemical evolution of the universe. The soft X-ray spectrum ...contains lines of the most abundant metals from N to Ni, which provide relatively accurate abundances that can be compared to supernova enrichment models. The accuracy of the abundances is currently limited by systematic uncertainties introduced by the available instruments and uncertainties in the modeling of the spectra, which are of the order of 20-30%. We discuss the possible gain of extending the current samples at low and high redshift. We conclude that expanding the samples would be expensive in terms of exposure time, but will not yield significantly improved results, because the current samples already reach the systematic limits. New instrumentation, like Astro-H2 and ATHENA, and improvements to the atomic databases are needed to make significant advances in this field.
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