arXiv subjects

K. Matsushita

Publications and source records attributed to K. Matsushita.

At least 19 recordsLinked to original sources

arXiv2026

Diagnosing the Fe line complex of the intracluster medium by XRISM high-resolution spectroscopy

We aim to test the validity of the CIE framework in the ICM by performing line diagnostics based mainly on resolved Fe-K emission lines. Methods. We analyse Resolve full-array spectra of 17 galaxy clusters. Prominent Fe-K line components (the Fe xxv w, x, y, z, and Fe xxvi Lyα1,2 lines) are removed from plasma emission models and instead fitted with Gaussian profiles, enabling direct measurements of line fluxes without relying on synthetic spectral models. Some cool-core systems show w/z ratios lower than predicted by about 20 per cent, and a broader w than z, consistent with resonant scattering effects. The y/x ratios exhibit marginal deviations from model predictions for some objects, suggesting possible origins of cascade process due to electron recombination and contribution from low-ionised Fe. The Fe Lyα2/Lyα1 ratios are globally close to the expected value of about 0.5, and the samples with good photon statistics prefer 0.55. This subtle excess is consistent with an unresolved contribution to Lyα2 from the magnetic-dipole (M1) transition, which is absent from one of the atomic codes considered here. More interestingly, systems at around 7 keV preferentially exhibit Lyα2/Lyα1 ratios above 0.55. Although the statistical significance of this trend is limited, it suggests that resolved Fe Lyα spectroscopy may provide a sensitive probe of additional atomic processes to collisional excitation, including dielectronic and radiative recombination and polarisation effects.

astro-ph.GA↗

arXiv2025

Chemical composition and enrichment of the Centaurus cluster core seen by XRISM/Resolve

Hot, X-ray emitting atmospheres pervading galaxy clusters are rich in metals, which have been synthesised and released by asymptotic giant branch (AGB) stars, core-collapse supernovae (SNcc) and Type Ia supernovae (SNIa) over cosmic history. This makes the intracluster medium (ICM) an ideal astrophysical system to constrain its chemical composition, hence ultimately understand metal production and enrichment on megaparsec scales. In this work, we take advantage of the unprecedented ~5 eV resolution offered by XRISM/Resolve to measure the chemical composition of the core of the bright, nearby, and metal-rich Centaurus cluster (287 ks) with unprecedented accuracy. We use these measurements to provide constraints on the stellar populations having enriched the cluster core. We derived the Fe abundance and its relative Si/Fe, S/Fe, Ar/Fe, Ca/Fe, Cr/Fe, Mn/Fe, and Ni/Fe ratios. We completed this high-resolution view with N/Fe, O/Fe, Ne/Fe, and Mg/Fe ratios obtained with XMM-Newton/RGS archival data. Similarly to the core of Perseus, we find that nine out of our 11 measured abundance ratios are formally consistent with the chemical composition of our Solar System. However, the (super-solar) N/Fe and (half-solar) Mg/Fe ratios significantly differ from Perseus and/or other systems, thus provide tension with the picture of a fully solar composition ubiquitous to all systems. In addition, possible uncertainties in O/Fe and Ne/Fe with atomic codes highlight the need for studying more systems at high spectral resolution to assess (or rule out) the universality of the ICM composition in clusters' cool cores. Combinations of (AGB+)SNcc+SNIa yield models can reproduce our observed X/Fe ratios in all cases. However, whether two distinct populations of SNIa are needed depends on the weight of our RGS measurements. We also briefly discuss the possibility of a multi-metallicity gas phase in this respect.

astro-ph.GA↗

arXiv2025

A XRISM/Resolve view of the dynamics in the hot gaseous atmosphere of M87

The XRISM/Resolve microcalorimeter directly measured the gas velocities in the core of the Virgo Cluster, the closest example of AGN feedback in a cluster. This proximity allows us to resolve the kinematic impact of feedback on scales down to 5 kpc. Our spectral analysis reveals a high velocity dispersion of $σ_v$=262 (+45 / -38) km/s near the AGN, which steeply declines to ~60 km/s between 5 and 25 kpc in the northwest direction. The observed line-of-sight bulk velocity in all regions is broadly consistent with the central galaxy, M87, with a mild trend toward blueshifted motions at larger radii. Systematic uncertainties have been carefully assessed and do not affect the measurements. The central velocities, if attributed entirely to isotropic turbulence, correspond to a transonic ICM at sub-6 kpc scales with three-dimensional Mach number 0.69 (+0.14 / -0.11) and a non-thermal pressure fraction of 21 (+7 / -5)%. Simple models of weak shocks and sound waves and calculations assuming isotropic turbulence both support the hypothesis that the velocity field reflects a mix of shock-driven expansion and turbulence. Compared to other clusters observed by XRISM to date, M87's central region stands out as the most kinematically disturbed, exhibiting both the highest velocity dispersion and the largest 3D Mach number, concentrated at the smallest physical scales.

astro-ph.GA↗

arXiv2024

Indications of an offset merger in Abell 3667

Abell 3667 is a nearby merging cluster with a prominent cold front and a pair of two bright radio relics. Assuming a head-on merger, the origin of the cold front is often considered to be a remnant of the cluster core stripped by its surrounding ICM. Some authors have proposed an offset merger scenario in which the subcluster core rotates after the first core crossing. This scenario can reproduce features such as the cold front and a pair of radio relics. To distinguish between these scenarios, we reanalyzed the ICM distribution and measured the line-of-sight bulk ICM velocity using the XMM-Newton PN data. In the unsharp masked image, we identify several ICM features. The notable feature is a RG1 vortex, which is a clockwise vortex-like enhancement with a radius of about 250 kpc connecting the first BCG to the radio galaxy (RG1). It is particularly enhanced near the north of the 1st BCG, which is named the BCG-N tail. The thermodynamic maps show that the ICM of the RG1 vortex has a relatively high abundance of 0.5-0.6 solar compared to the surrounding regions. The ICM of the BCG-E tail also has a high abundance and low pseudo-entropy and can be interpreted as a remnant of the cluster core's ICM. Including its arc-like shape, the RG1 vortex supports the idea that the ICM around the cluster center is rotating, which is natural for an offset merger scenario. The results of the line-of-sight bulk ICM velocity measurements show that the ICM around the BCG-N tail is redshifted with a velocity difference of 940+/-440 km/s compared to the optical redshift of the first BCG. We obtain other indications of variations in the line-of-sight velocity of the ICM and discuss these in the context of an offset merger.

astro-ph.HE↗

arXiv2024

Revisiting the abundance pattern and charge-exchange emission in the M82 centre

The interstellar medium (ISM) in starburst galaxies contains plenty of chemical elements synthesised by core-collapse supernova explosions. By measuring the abundances of these metals, we can study the chemical enrichment within galaxies and the transportation of metals into circumgalactic environments through powerful outflows. We perform the spectral analysis of the X-ray emissions from the M82 core using the Reflection Grating Spectrometer (RGS) onboard XMM-Newton to accurately estimate the metal abundances in the ISM. We analyse over 300 ks of RGS data observed with fourteen position angles, covering an 80 arcsec cross-dispersion width. We employ multi-temperature thermal plasma components in collisional ionisation equilibrium (CIE) to reproduce the observed spectra, each exhibiting different spatial broadenings. The O vii band CCD image shows a broader distribution compared to those for O viii and Fe-L bands. The O viii line profiles have a prominent double-peaked structure, corresponding to the northward and southward outflows. The O vii triplet feature exhibits marginal peaks, and a single CIE component, convolved with the O vii band image, approximately reproduces the spectral shape. Combining a CIE model with a charge-exchange emission model also successfully reproduces the O vii line profiles. However, the ratio of these two components varies significantly with the observed position angles, which is physically implausible. Spectral fitting of the broadband spectra suggests a multi-temperature phase in the ISM, approximated by three components at 0.1, 0.4, and 0.7 keV. Notably, the 0.1 keV component exhibits a broader distribution than the 0.4 and 0.7 keV plasmas. The derived abundance pattern shows super-solar N/O, solar Ne/O and Mg/O, and half-solar Fe/O ratios. These results indicate the chemical enrichments by core-collapse supernovae in starburst galaxies.

astro-ph.GA↗

arXiv2022

XMM-Newton view of the shock heating in an early merging cluster, CIZA J1358.9$-$4750

CIZA J1358.9-4750 is a nearby galaxy cluster in the early phase of a major merger. The two-dimensional temperature map using XMM-Newton EPIC-PN observation confirms the existence of a high temperature region, which we call the "hot region", in the "bridge region" connecting the two clusters. The ~ 500 kpc wide region between the southeast and northwest boundaries also has higher pseudo pressure compared to the unshocked regions, suggesting the existence of two shocks. The southern shock front is clearly visible in the X-ray surface brightness image and has already been reported by Kato et al. (2015). The northern one, on the other hand, is newly discovered. To evaluate their Mach number, we constructed a three-dimensional toy merger model with overlapping shocked and unshocked components in line of sight. The unshocked and preshock ICM conditions are estimated based on those outside the interacting bridge region assuming point symmetry. The hot region spectra are modeled with two-temperature thermal components, assuming that the shocked condition follows the Rankin-Hugoniot relation with the preshock condition. As a result, the shocked region is estimated to have a line-of-sight depth of ~ 1 Mpc with a Mach number of ~ 1.3 in the southeast shock and ~ 1.7 in the northwest shock. The age of the shock waves is estimated to be ~ 260 Myr. This three dimensional merger model is consistent with the Sunyaev-Zeldovich signal obtained using the Planck observation within the CMB fluctuations. The total flow of the kinetic energy of the ICM through the southeast shock was estimated to be ~ 2.2 x $10^{42}$ erg/s. Assuming that 10 % of this energy is converted into ICM turbulence, the line-of-sight velocity dispersion is calculated to be ~ 200 km/s, which is basically resolvable via coming high spectral resolution observations.

astro-ph.GA↗

arXiv2019

Unveiling the Galaxy Cluster - Cosmic Web Connection with X-ray observations in the Next Decade

In recent years, the outskirts of galaxy clusters have emerged as one of the new frontiers and unique laboratories for studying the growth of large scale structure in the universe. Modern cosmological hydrodynamical simulations make firm and testable predictions of the thermodynamic and chemical evolution of the X-ray emitting intracluster medium. However, recent X-ray and Sunyaev-Zeldovich effect observations have revealed enigmatic disagreements with theoretical predictions, which have motivated deeper investigations of a plethora of astrophysical processes operating in the virialization region in the cluster outskirts. Much of the physics of cluster outskirts is fundamentally different from that of cluster cores, which has been the main focus of X-ray cluster science over the past several decades. A next-generation X-ray telescope, equipped with sub-arcsecond spatial resolution over a large field of view along with a low and stable instrumental background, is required in order to reveal the full story of the growth of galaxy clusters and the cosmic web and their applications for cosmology.

astro-ph.CO↗

arXiv2018

Constraints on the Chemical Enrichment History of the Perseus Cluster of Galaxies from High-Resolution X-ray Spectroscopy

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%, while the constraints on Si/Fe, S/Fe, and Cr/Fe are at the 15% level, and Mn/Fe is measured with a 20% uncertainty. The average biases in determining the chemical composition using archival CCD spectra from $XMM$-$Newton$ and $Suzaku$ range typically from 15-40%. A simple model in which the enrichment pattern in the Perseus Cluster core and the proto-solar nebula are identical gives a surprisingly good description of the high-resolution X-ray spectroscopy results, with $χ^2=10.7$ for 10 d.o.f. 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.

astro-ph.HE↗

arXiv2015

Suzaku observations of a shock front tracing the western edge of the giant radio halo in the Coma Cluster

We present the results of new Suzaku observations of the Coma Cluster, the X-ray brightest, nearby, merging system hosting a well studied, typical giant radio halo. It has been previously shown that, on the western side of the cluster, the radio brightness shows a much steeper gradient compared to other azimuths. XMM-Newton and Planck revealed a shock front along the southern half of the region associated with this steep radio gradient, suggesting that the radio emission is enhanced by particle acceleration associated with the shock passage. Suzaku demonstrates for the first time that this shock front extends northwards, tracing the entire length of the western edge of the Coma radio halo. The shock is detected both in the temperature and X-ray surface brightness distributions and has a Mach number of around $\mathcal{M}\sim1.5$. The locations of the surface brightness edges align well with the edge of the radio emission, while the obtained temperature profiles seem to suggest shocks located 125-185 kpc further out in radius. In addition, the shock strengths derived from the temperature and density jumps are in agreement when using extraction regions parallel to the radio halo edge, but become inconsistent with each other when derived from radial profiles centred on the Coma Cluster core. It is likely that, beyond mere projection effects, the geometry of the shock is more complex than a front with a single, uniform Mach number and an approximately spherically symmetric shape.

astro-ph.HE↗

arXiv2015

Central Mass Profiles of the Nearby Cool-core Galaxy Clusters Hydra A and A478

We perform a weak-lensing study of the nearby cool-core galaxy clusters, Hydra A ($z=0.0538$) and A478 ($z=0.0881$), of which brightest cluster galaxies (BCGs) host powerful activities of active galactic nuclei (AGNs). For each cluster, the observed tangential shear profile is well described either by a single Navarro--Frenk--White model or a two-component model including the BCG as an unresolved point mass. For A478, we determine the BCG and its host-halo masses from a joint fit to weak-lensing and stellar photometry measurements. We find that the choice of initial mass functions (IMFs) can introduce a factor of two uncertainty in the BCG mass, whereas the BCG host halo mass is well constrained by data. We perform a joint analysis of weak-lensing and stellar kinematics data available for the Hydra A cluster, which allows us to constrain the central mass profile without assuming specific IMFs. We find that the central mass profile ($r<300$kpc) determined from the joint analysis is in excellent agreement with those from independent measurements, including dynamical masses estimated from the cold gas disk component, X-ray hydrostatic total mass estimates, and the central stellar mass estimated based on the Salpeter IMF. The observed dark-matter fraction around the BCG for Hydra A is found to be smaller than those predicted by adiabatic contraction models, suggesting the importance of other physical processes, such as the the AGN feedback and/or dissipationless mergers.

astro-ph.CO↗

arXiv2014

ASTRO-H White Paper - High Resolution Spectroscopy of Interstellar and Circumgalactic Gas in the Milky Way and Other Galaxies

We describe the potential of high resolution imaging spectroscopy with the SXS on ASTRO-H to advance our understanding of the interstellar- and circumgalactic media of our own Galaxy, and other galaxies. Topics to be addressed range from absorption spectroscopy of dust in the Galactic interstellar medium, to observations to constrain the total mass-, metal-, and energy flow out of starburst galaxies.

astro-ph.HE↗

arXiv2014

ASTRO-H White Paper - Clusters of Galaxies and Related Science

The next generation X-ray observatory ASTRO-H will open up a new dimension in the study of galaxy clusters by achieving for the first time the spectral resolution required to measure velocities of the intracluster plasma, and extending at the same time the spectral coverage to energies well beyond 10 keV. This white paper provides an overview of the capabilities of ASTRO-H for exploring gas motions in galaxy clusters including their cosmological implications, the physics of AGN feedback, dynamics of cluster mergers as well as associated high-energy processes, chemical enrichment of the intracluster medium, and the nature of missing baryons and unidentified dark matter.

astro-ph.HE↗

arXiv2014

Temperature and Entropy Profiles to the Virial Radius of Abell 1246 Cluster Observed with Suzaku

We report properties of the intracluster medium (ICM) in Abell~1246 to the virial radius ($r_{200}$) and further outside as observed with Suzaku. The ICM emission is clearly detected to $r_{200}$, and we derive profiles of electron temperature, density, entropy, and cluster mass based on the spectral analysis. The temperature shows variation from $\sim 7$ keV at the central region to $\sim 2.5$ keV around $r_{200}$. The total mass in $r_{500}$ is $(4.3 \pm 0.4) \times 10^{14}~M_{\odot}$, assuming hydrostatic equilibrium. At $r>r_{500}$, the hydrostatic mass starts to decline and we, therefore, employ the total mass within $r_{200}$ based on weak-lens mass profile obtained from a sample of lower mass clusters. This yields the gas mass fraction at $r_{200}$ consistent with the cosmic baryon fraction, i.e. $\sim 17$%. The entropy profile indicates a flatter slope than that of the numerical simulation, particularly in $r>r_{500}$. These tendencies are similar to those of other clusters observed with Suzaku. We detect no significant ICM emission outside of $r_{200}$, and $2σ$ upper limits of redshifted OVII and OVIII line intensities are constrained to be less than 2.9 and $5.6\times 10^{-7}$ photons cm$^{-2}$ s$^{-1}$ arcmin$^{-2}$, respectively. The OVII line upper limit indicates $n_{\rm H}< 4.7\times 10^{-5}$ cm$^{-3}$ ($Z/0.2~Z_{\odot}$)$^{-1/2}$ ($L/20~{\rm Mpc}$)$^{-1/2}$, which corresponds to an overdensity, $δ<160$ ($Z/0.2~Z_{\odot}$)$^{-1/2}$ ($L/20~{\rm Mpc}$)$^{-1/2}$.

astro-ph.CO↗

arXiv2014

Universal Profiles of the Intracluster Medium from Suzaku X-Ray and Subaru Weak Lensing Obesrvations

We conduct a joint X-ray and weak-lensing study of four relaxed galaxy clusters (Hydra A, A478, A1689 and A1835) observed by both Suzaku and Subaru out to virial radii, with an aim to understand recently-discovered unexpected feature of the ICM in cluster outskirts. We show that the average hydrostatic-to-lensing total mass ratio for the four clusters decreases from \sim 70% to \sim 40% as the overdensity contrast decreases from 500 to the virial value.The average gas mass fraction from lensing total mass estimates increases with cluster radius and agrees with the cosmic mean baryon fraction within the virial radius, whereas the X-ray-based gas fraction considerably exceeds the cosmic values due to underestimation of the hydrostatic mass. We also develop a new advanced method for determining normalized cluster radial profiles for multiple X-ray observables by simultaneously taking into account both their radial dependence and multivariate scaling relations with weak-lensing masses. Although the four clusters span a range of halo mass, concentration, X-ray luminosity and redshift, we find that the gas entropy, pressure, temperature and density profiles are all remarkably self-similar when scaled with the lensing M_200 mass and r_200 radius.The entropy monotonically increases out to \sim 0.5r_200 following the accretion shock heating model K(r)\propto r^1.1, and flattens at \simgt 0.5r_200.The universality of the scaled entropy profiles indicates that the thermalization mechanism over the entire cluster region (>0.1r_200) is controlled by gravitation in a common to all clusters, although the heating efficiency in the outskirts needs to be modified from the standard law.The bivariate scaling functions of the gas density and temperature reveal that the flattening of the outskirts entropy profile is caused by the steepening of the temperature, rather than the flattening of the gas density.

astro-ph.CO↗

arXiv2013

Gas bulk motion in the Perseus cluster measured with SUZAKU

We present the results from Suzaku observations of the Perseus galaxy cluster, which is relatively close, the brightest in the X-ray sky and a relaxed object with a cool core. A number of exposures of central regions and offset pointing with the X-ray Imaging Spectrometer cover a region within radii of 20'-30'. The central data are used to evaluate the instrumental energy-scale calibration with accuracy confirmed to within around 300 km/s, by the spatial and temporal variation of the instruments. These deep and well-calibrated data are used to measure X-ray redshifts of the intracluster medium. A hint of gas bulk motion, with radial velocity of about -(150-300) km/s, relative to the main system was found at 2-4 arcmin (45-90kpc) west of the cluster center, where an X-ray excess and a cold front were found previously. No other velocity structure was discovered. Over spatial scales of 50-100kpc and within 200kpc radii of the center, the gas-radial-velocity variation is below 300 km/s, while over scales of 400 kpc within 600 kpc radii, the variation is below 600 km/s. These X-ray redshift distributions are compared spatially with those of optical member galaxies for the first time in galaxy clusters. Based on X-ray line widths gas turbulent velocities within these regions are also constrained within 1000-3000 km/s. These results of gas dynamics in the core and larger scales in association with cluster merger activities are discussed and future potential of high-energy resolution spectroscopy with ASTRO-H is considered.

astro-ph.CO↗

arXiv2013

Thermodynamics of the Coma Cluster Outskirts

We present results from a large mosaic of Suzaku observations of the Coma Cluster, the nearest and X-ray brightest hot, dynamically active, non-cool core system, focusing on the thermodynamic properties of the ICM on large scales. For azimuths not aligned with an infalling subcluster towards the southwest, our measured temperature and X-ray brightness profiles exhibit broadly consistent radial trends, with the temperature decreasing from about 8.5 keV at the cluster center to about 2 keV at a radius of 2 Mpc, which is the edge of our detection limit. The SW merger significantly boosts the surface brightness, allowing us to detect X-ray emission out to ~2.2 Mpc along this direction. Apart from the southwestern infalling subcluster, the surface brightness profiles show multiple edges around radii of 30-40 arcmin. The azimuthally averaged temperature profile, as well as the deprojected density and pressure profiles, all show a sharp drop consistent with an outward propagating shock front located at 40 arcmin, corresponding to the outermost edge of the giant radio halo observed at 352 MHz with the WSRT. The shock front may be powering this radio emission. A clear entropy excess inside of r_500 reflects the violent merging events linked with these morphological features. Beyond r_500, the entropy profiles of the Coma Cluster along the relatively relaxed directions are consistent with the power-law behavior expected from simple models of gravitational large-scale structure formation. The pressure is also in agreement at these radii with the expected values measured from SZ data from the Planck satellite. However, due to the large uncertainties associated with the Coma Cluster measurements, we cannot yet exclude an entropy flattening in this system consistent with that seen in more relaxed cool core clusters.

astro-ph.CO↗

arXiv2013

Metal-mass-to-light ratios of the Perseus cluster out to the virial radius

We analyzed XMM-Newton data of the Perseus cluster out to $\sim$1 Mpc, or approximately half the virial radius. Using the flux ratios of Lyalpha lines of H-like Si and S to Kalpha line of He-like Fe, the abundance ratios of Si/Fe and S/Fe of the intracluster medium (ICM) were derived using the APEC plasma code v2.0.1. The temperature dependence of the line ratio limits the systematic uncertainty in the derived abundance ratio. The Si/Fe and S/Fe in the ICM of the Perseus cluster show no radial gradient. The emission-weighted averages of the Si/Fe and S/Fe ratios outside the cool core are 0.91 +- 0.08 and 0.93 +- 0.10, respectively, in solar units according to the solar abundance table of Lodders (2003). These ratios indicate that most Fe was synthesized by supernovae Ia. We collected K-band luminosities of galaxies and calculated the ratio of Fe and Si mass in the ICM to K-band luminosity, iron-mass-to-light ratio (IMLR) and silicon-mass-to-light ratio (SMLR). Within $\sim$1 Mpc, the cumulative IMLR and SMLR increase with radius. Using Suzaku data for the northwest and east directions, we also calculated the IMLR out to $\sim$ 1.8 Mpc, or about the virial radius. We constrained the SMLR out to this radius and discussed the slope of the initial mass function of stars in the cluster. Using the cumulative IMLR profile, we discuss the past supernova Ia rate.

astro-ph.CO↗

arXiv2011

ORIGIN: Metal Creation and Evolution from the Cosmic Dawn

ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z ~ 0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs.

astro-ph.IM↗