Search arXiv⌕ Search

arXiv subjects

Peter Predehl

Publications and source records attributed to Peter Predehl.

At least 19 recordsLinked to original sources
arXiv2026

The SRG/eROSITA diffuse soft X-ray background II. spectra and morphology of the eROSITA bubbles in the western Galactic hemisphere

The eROSITA bubbles (eRObub) were discovered in 2020 in the first SRG/eROSITA All-Sky Survey, and are among the most extended structures in the X-ray sky. Using eROSITA all-sky maps and spatially resolved spectra, we aim to infer the three-dimensional structure and measure the hot gas properties of the eRObub. We fit spectra binned to a constant S/N and high-S/N spectra from custom regions to examine gas properties in more detail. We fit the morphology of eRObub with a parametrised geometrical model that describes a blast wave propagating into an idealised Galactic halo from the centre. We found the interior of the western eRObub is best characterised by two emission components with relatively uniform temperatures: a hotter component at $kT=0.60\pm0.02$ keV, and a colder one at $kT=0.21^{+0.03}_{-0.01}$ keV, where the latter's emission measure is about five times higher on average. Our spectra suggest sub-solar abundances ($Z=0.2\pm0.1 Z_\odot$), consistent with expectations for the Galactic halo, while we find no conclusive evidence for $\alpha$-element enhancement. In contrast, the North Polar Spur exhibits higher abundances ($Z>0.5 Z_\odot$), which, at face value, disfavours a common origin. We spectrally confirm an apparent cool shell at $kT\sim0.18$-$0.2$ keV surrounding the northern eRObub, assuming collisional ionisation equilibrium. We found no noticeable difference in X-ray emission in regions overlapping with the Fermi Bubbles. Our geometrical model suggests that the horizontal size of both eRObub is well-constrained (semi-minor axis $\sim 6$ kpc), but their vertical extent is uncertain, as the observed X-ray emission is almost insensitive to the existence and location of a bubble cap. Additionally, a tilt ($\sim 30^{\circ}$) towards $l\sim 220^{\circ}$ is needed to reproduce the projected image of the northern eRObub, whereas the southern bubble requires little tilt.

astro-ph.HE↗
arXiv2025

On the origin of the X-ray emission surrounding PSR B0656+14 in the eROSITA Cal-PV data

We present a cautionary assessment of the extended X-ray emission around PSR B0656+14 in eROSITA Cal-PV data in response to the work of Niu et al. 2025 (arXiv:2501.17046). The eROSITA PSF model is known to underestimate emission in the wings beyond 1'. This prevents a reliable detection of faint nebular emission around PSR B0656+14 as claimed in arXiv:2501.17046. In addition, spectral analysis shows the surrounding diffuse X-rays can be fitted with the same 2BB+PL model as the pulsar's emission itself. This strongly invalidates the interpretation by the authors of arXiv:2501.17046 that the X-ray emission in the (4-10)' region is associated with the degree-scale gamma-ray halo recently found by the High-Altitude Water Cherenkov Observatory (HAWC), and shows that it originates from the pulsar due to the wings of the PSF.

astro-ph.HE↗
arXiv2024

The hot circumgalactic medium in the eROSITA All-Sky Survey III. Star-forming and quiescent galaxies

The circumgalactic medium (CGM), as the gas repository for star formation, might contain the answer to the mysterious galaxy quenching and bimodal galaxy population origin. We measured the X-ray emission of the hot CGM around star-forming and quiescent galaxies. We detect extended X-ray emission from the hot CGM around star-forming galaxies with $\log(M_*/M_\odot)>11.0$ and quiescent galaxies with $\log(M_*/M_\odot)>10.5$, extending out to $R_{\rm 500c}$. $L_{\rm X, CGM}$ of star-forming galaxies with median stellar masses $\log(M_{\rm *,med}/M_\odot) = 10.7, 11.1, 11.3$ are approximately $0.8\,, 2.3\,, 4.0 \times 10^{40}\,\rm erg/s$, while for quiescent galaxies with $\log(M_{\rm *,med}/M_\odot) = 10.8, 11.1, 11.4$, they are $1.1\,, 6.2\,, 30 \times 10^{40}\,\rm erg/s$. Notably, quiescent galaxies with $\log(M_{\rm *,med}/M_\odot) > 11.0$ exhibit brighter hot CGM than their star-forming counterparts. In halo mass bins, we detect similar X-ray emission around star-forming and quiescent galaxies with $\log(M_{\rm 200m}/M_\odot) > 12.5$, suggesting that galaxies in the same mass dark matter halos host equally bright hot CGM. We emphasize the observed $L_{\rm X, CGM} - M_{\rm 500c}$ relations of star-forming and quiescent galaxies are sensitive to the stellar-to-halo mass relation (SHMR). A comparison with cosmological hydrodynamical simulations (EAGLE, TNG100, and SIMBA) reveals varying degrees of agreement, contingent on the simulation and the specific stellar or halo mass ranges considered. Either selected in stellar mass or halo mass, the star-forming galaxies do not host brighter stacked X-ray emission from the hot CGM than their quiescent counterparts at the same mass range. The result provides useful constraints on the extent of feedback's impacts as a mechanism for quenching star formation as implemented in current cosmological simulations.

astro-ph.GA↗
arXiv2024

Morphological Evidence for the eROSITA Bubbles Being Giant and Distant Structures

There are two contradictory views of the eROSITA bubbles: either a 10 kpc-scale pair of giant bubbles blown by the Galactic center (GC), or a 100 pc-scale local structure coincidentally located in the direction of GC. A key element of this controversy is the distance to the bubbles. Based on the 3D dust distribution in the Galactic plane, we found three isolated, distant (500-800 pc) clouds at intermediate Galactic latitudes. Their projected morphologies perfectly match the X-ray shadows on the defining features of the north eROSITA bubble, i.e., the North Polar Spur (NPS) and the Lotus Petal Cloud (LPC), indicating that both the NPS and LPC are distant with a distance lower limit of nearly 1kpc. In the X-ray dark region between the NPS and LPC, we found a few polarized radio arcs and attributed them to the bubble's shock front. These arcs match up perfectly with the outer border of the NPS and LPC and provide a way to define the bubble's border. The border defined in this way can be well described by the line-of-sight tangent of a 3D skewed cup model rooted in the GC. We conclude that, instead of being two independent, distant features, NPS and LPC compose a single, giant bubble, which, therefore, is most plausibly a 10-kpc scale bubble rooted at the GC.

astro-ph.GA↗
arXiv2024

The hot circumgalactic medium in the eROSITA All-Sky Survey I. X-ray surface brightness profiles

The circumgalactic medium (CGM) provides the material needed for galaxy formation and influences galaxy evolution. The hot ($T>10^6K$) CGM is poorly detected around galaxies with stellar masses ($M_*$) lower than $3\times10^{11}M_\odot$ due to the low surface brightness. We used the X-ray data from the first four SRG/eROSITA All-Sky Surveys (eRASS:4). Based on the SDSS spectroscopic survey and halo-based group finder algorithm, we selected central galaxies with spectroscopic redshifts of $z_{\rm spec}<0.2$ and stellar masses of $10.0<\log(M_*/M_\odot)<11.5$ (85,222 galaxies) -- or halo masses of $11.5<\log(M_{\rm 200m}/M_\odot)<14.0$ (125,512 galaxies). By stacking the X-ray emission around galaxies, masking the detected X-ray point sources and carefully modeling the X-ray emission from the unresolved active galactic nuclei (AGN) and X-ray binaries (XRB), we obtain the X-ray emission from the hot CGM. We detected the X-ray emission around MW-mass and more massive central galaxies extending up to the virial radius ($R_{\rm vir}$). We used a $\beta$ model to describe the X-ray surface brightness profile and found $\beta =0.43^{+0.10}_{-0.06}\,(0.37^{+0.04}_{-0.02})$ for MW-mass (M31-mass) galaxies.We estimated the baryon budget of the hot CGM and obtained a value that is lower than the prediction of $\Lambda$CDM cosmology, indicating significant gas depletion in these halos. We extrapolated the hot CGM profile measured within $R_{\rm vir}$ to larger radii and found that within $\approx 3 R_{\rm vir}$, the baryon budget is close to the $\Lambda$CDM cosmology prediction. Our results set a firm footing for the presence of the hot CGM around such galaxies. These measurements constitute a new benchmark for galaxy evolution models and possible implementations of feedback processes therein.

astro-ph.GA↗
arXiv2024

The hot circumgalactic medium in the eROSITA All-Sky Survey II. Scaling relations between X-ray luminosity and galaxies' mass

Understanding how the properties of galaxies relate to the properties of the hot circum-galactic medium (CGM) around them can constrain galaxy evolution models. We measured the X-ray luminosity of the hot CGM based on the surface brightness profiles of central galaxy samples measured from Spectrum Roentgen Gamma (SRG)/eROSITA all-sky survey data. We related the X-ray luminosity to the galaxies' stellar and halo mass, and we compared the observed relations to the self-similar model and intrinsic (i.e., not forward-modeled) output of the IllustrisTNG, EAGLE, and SIMBA simulations. The average hot CGM X-ray luminosity ($L_{\rm X,CGM}$) correlates with the galaxy's stellar mass ($M_*$). It increases from $(1.6 \pm 2.1)\times10^{39} \rm erg\,s^{-1}$ to $(3.4 \pm 0.3)\times10^{41} \rm erg\,s^{-1}$, when $\log(M_*)$ increases from 10.0 to 11.5. A power law describes the correlation as $\log(L_{\rm X,CGM})= (2.4\pm 0.1)\times \log(M_*)+(14.6\pm1.5)$. The hot CGM X-ray luminosity as a function of halo mass is measured within $\log(M_{\rm 500c})=11.3-13.7$, extending our knowledge of the scaling relation by more than two orders of magnitude. $L_{\rm X,CGM}$ increases with $M_{\rm 500c}$ from $(3.0 \pm 1.6)\times10^{39}\ \rm erg\,s^{-1}$ at $\log(M_{\rm 500c})=11.3$ to $(1.3 \pm 0.1)\times10^{42}\ \rm erg\,s^{-1}$ at $\log(M_{\rm 500c})=13.7$. The relation follows a power law of $\log(L_{\rm X,CGM})= (1.32\pm 0.05)\times \log(M_{\rm 500c})+(24.1\pm0.7)$. Our observations highlight the necessity of non-gravitational processes at the galaxy group scale while suggesting these processes are sub-dominant at the galaxy scale. We show that the outputs of current cosmological galaxy simulations generally align with the observational results uncovered here but with possibly important deviations in selected mass ranges.

astro-ph.GA↗
arXiv2023

Broadband maps of eROSITA and their comparison with the ROSAT survey

By June of 2020, the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Spectrum Roentgen Gamma observatory had completed its first of the planned eight X-ray all-sky survey (eRASS1). The large effective area of the X-ray telescope makes it ideal for a survey of the faint X-ray diffuse emission over half of the sky with an unprecedented energy resolution and position accuracy. In this work, we produce the X-ray diffuse emission maps of the eRASS1 data with a current calibration, covering the energy range from 0.2 to 8.0 keV. We validated these maps by comparison with X-ray background maps derived from the ROSAT All Sky Survey (RASS). We generated X-ray images with a pixel area of 9 arcmin$^2$ using the observations available to the German eROSITA consortium. The contribution of the particle background to the photons was subtracted from the final maps. We also subtracted all the point sources above a flux threshold dependent on the goal of the subtraction, exploiting the eRASS1 catalog that will soon be available. The accuracy of the eRASS1 maps is shown by a flux match to the RASS X-ray maps, obtained by converting the eROSITA rates into equivalent ROSAT count rates in the standard ROSAT energy bands R4, R5, R6, and R7, within 1.25$\sigma$. We find small residual deviations in the R4, R5, and R6 bands, where eROSITA tends to observe lower flux than ROSAT (~11%), while a better agreement is achieved in the R7 band (~1%). The eRASS maps exhibit lower noise levels than RASS maps at the same resolution above 0.3 keV. We report the average surface brightness and total flux of different large sky regions as a reference. The detection of faint emission from diffuse hot gas in the Milky Way is corroborated by the consistency of the eRASS1 and RASS maps shown in this paper and by their comparable flux dynamic range.

astro-ph.GA↗
arXiv2023

The High Energy X-ray Probe (HEX-P): Instrument and Mission Profile

The High Energy X-ray Probe is a proposed NASA probe-class mission that combines the power of high angular resolution with a broad X-ray bandpass to provide the necessary leap in capabilities to address the important astrophysical questions of the next decade. HEX-P achieves breakthrough performance by combining technologies developed by experienced international partners. HEX-P will be launched into L1 to enable high observing efficiency. To meet the science goals, the payload consists of a suite of co-aligned X-ray telescopes designed to cover the 0.2 - 80 keV bandpass. The High Energy Telescope (HET) has an effective bandpass of 2 - 80 keV, and the Low Energy Telescope (LET) has an effective bandpass of 0.2 - 20 keV. The combination of bandpass and high observing efficiency delivers a powerful platform for broad science to serve a wide community. The baseline mission is five years, with 30% of the observing time dedicated to the PI-led program and 70% to a General Observer (GO) program. The GO program will be executed along with the PI-led program.

astro-ph.IM↗
arXiv2023

The High Energy X-ray Probe (HEX-P): resolving the nature of Sgr A* flares, compact object binaries and diffuse X-ray emission in the Galactic Center and beyond

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ($<10"$ FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far superior to current facilities' (including XMM-Newton and NuSTAR). These capabilities will enable revolutionary new insights into a variety of important astrophysical problems. We present scientific objectives and simulations of HEX-P observations of the Galactic Center (GC) and Bulge. We demonstrate the unique and powerful capabilities of the HEX-P observatory for studying both X-ray point sources and diffuse X-ray emission. HEX-P will be uniquely equipped to explore a variety of major topics in Galactic astrophysics, allowing us to (1) investigate broad-band properties of X-ray flares emitted from the supermassive black hole (BH) at Sgr A* and probe the associated particle acceleration and emission mechanisms; (2) identify hard X-ray sources detected by NuSTAR and determine X-ray point source populations in different regions and luminosity ranges; (3) determine the distribution of compact object binaries in the nuclear star cluster and the composition of the Galactic Ridge X-ray emission; (4) identify X-ray transients and measure fundamental parameters such as BH spin; (5) find hidden pulsars in the GC; (6) search for BH-OB binaries and hard X-ray flares from young stellar objects in young massive clusters; (7) measure white dwarf (WD) masses of magnetic CVs to deepen our understanding of CV evolution and the origin of WD magnetic fields; (8) explore primary particle accelerators in the GC in synergy with future TeV and neutrino observatories; (9) map out cosmic-ray distributions by observing non-thermal X-ray filaments; (10) explore past X-ray outbursts from Sgr A* through X-ray reflection components from giant molecular clouds.

astro-ph.HE↗
arXiv2023

A detailed look at the thermal and non-thermal X-ray emission from the Vela supernova remnant with SRG/eROSITA

Aims. Our goal is the characterization of the hot ejecta and shocked interstellar medium (ISM) associated to the Vela supernova remnant (SNR), as well as the relativistic electrons injected into the ambient medium by its central pulsar. To achieve this, we analyze the X-ray data set of Vela acquired by SRG/eROSITA during its first four all-sky surveys. Methods. Apart from multi-band imaging, a quantitative view of the physical parameters affecting the observed thermal and non-thermal emission is obtained by performing spatially resolved X-ray spectroscopy of over 500 independent regions using multi-component spectral models. Results. Imaging demonstrates that the X-ray emission of the Vela SNR consists of at least three morphologically distinct components, with shell-like structures dominating below 0.6 keV, radial outward-directed features becoming apparent at medium energies, and the pulsar wind nebula (PWN) dominating the hard emission above 1.4 keV. Our spectroscopy reveals a highly structured distribution of X-ray absorption column densities, which intriguingly appears anticorrelated with optical extinction measurements. We find evidence for multiple ejecta clumps inside and outside the shell, within which we find a strongly supersolar concentration of neon and magnesium relative to oxygen. This includes the bright shrapnel D, in which we separate shocked ISM in the soft bow-shock from a hot, ejecta-rich clump at its apex, based on the new data. Finally, we find an extremely extended, smoothly decreasing distribution of synchrotron emission from the PWN, which extends up to 14 pc from the pulsar, with a total X-ray luminosity of $1.5\times10^{-3}$ of the pulsar's spin-down power. The extended emission likely traces a relativistic electron population in an ISM-level magnetic field, which requires the existence of a TeV counterpart powered by inverse Compton radiation.

astro-ph.HE↗
arXiv2023

SRG/eROSITA and XMM-Newton observations of Vela Jr

The Vela supernova remnant complex is a region containing at least three supernova remnants: Vela, Puppis A, and Vela Jr. With the launch of the spectro-imaging X-ray telescope eROSITA on board the Spectrum Roentgen Gamma (SRG) mission, it became possible to observe the one degree wide Vela Jr in its entirety. Although several previous pointed Chandra and XMM-Newton observations are available, it is only the second time after the ROSAT all-sky survey that the whole remnant was observed in X-rays with homogeneous sensitivity. Vela Jr is one of the few remnants emitting in the TeV band, making it an important object in shock acceleration studies. However, the age and distance determination using X-ray emission is largely hampered by the presence of the Vela SNR along the same line. With the eROSITA data set our aim is to characterize the emission of Vela Jr and distinguish it from Vela emission, and also to characterize the spectral emission of the inner remnant. We processed the eROSITA data dividing the whole remnant into seven different regions. In addition, images of the whole remnant were employed to pinpoint the position of the geometric center and constrain the proper motion of the CCO. We also employed archival XMM-Newton pointed observations of the NW rim to determine the cutoff energy of the electrons and the expansion velocity. We find the magnetic field can vary between 2 $\mu$G and 16 $\mu$G in the NW rim. We also find that the remnant spectrum is uniformly featureless in most regions, except for two inner regions where an extra thermal model component improves the fit. We obtain new coordinates for the geometric remnant center, resulting in a separation of only 35.2 $\pm$ 15.8" from the position of the CCO. As a result, we reinforce the association between the CCO and a proposed faint optical/IR counterpart.

astro-ph.HE↗
arXiv2022

The eROSITA Final Equatorial Depth Survey (eFEDS): X-ray emission around star-forming and quiescent galaxies at $0.05<z<0.3$

We aim at characterizing the hot phase of the Circum-Galactic Medium in a large sample of galaxies. We stack X-ray events from the SRG/eROSITA eFEDS survey around central galaxies in the GAMA 9hr field to construct radially projected soft X-ray luminosity profiles as a function of their stellar mass and specific star formation rate. We consider samples of quiescent (star-forming) galaxies in the stellar mass range $2\times 10^{10}$ -- $10^{12}$ M$_\odot$ ($3\times 10^9$ -- $6\times10^{11}$ M$_\odot$). For quiescent galaxies, the X-ray profiles are clearly extended throughout the available mass range; however, the measured profile is likely biased high due to projection effects, as these galaxies tend to live in dense and hot environments. For the most massive star forming samples ($\geq10^{11}$ M$_\odot$), there is a hint of detection of extended emission. For star-forming galaxies with $< 10^{11}$ M$_\odot$ the X-ray stacked profiles are compatible with unresolved sources and consistent with the expected emission from faint Active Galactic Nuclei and X-ray binaries. We measure for the first time the mean relation between average X-ray luminosity and stellar mass separately for quiescent and star-forming galaxies. High-mass ($\geq 10^{11}$ M$_\odot$) star-forming or quiescent galaxies follow the expected scaling of virialized hot haloes, while lower mass star-forming galaxies show a less prominent luminosity and a weaker dependence on stellar mass, consistent with empirical models of the weak AGN population. When comparing our results with state-of-the art numerical simulations, we find an overall consistency on large ($>80$ kpc) scales at masses $\geq 10^{11}$ M$_\odot$, but disagreement on the small scales, where brighter than observed compact cores are predicted. Simulations also do not predict the clear differentiation that we observe between quiescent and star-forming galaxies.

astro-ph.GA↗
arXiv2021

A global view of shocked plasma in the supernova remnant Puppis A provided by SRG/eROSITA

Context. Puppis A is a medium-age supernova remnant (SNR), which is visible as a very bright extended X-ray source. While numerous studies have investigated individual features of the SNR, at this time, no comprehensive study of the entirety of its X-ray emission exists. Aims. Using field-scan data acquired by the SRG/eROSITA telescope during its calibration and performance verification phase, we aim to investigate the physical conditions of shocked plasma and the distribution of elements throughout Puppis A. Methods. Using broad- and narrow-band imaging, we investigate the large-scale distribution of absorption and plasma temperature as well as typical emission lines. This approach is complemented by spatially resolved spectral analysis of the shocked plasma in Puppis A, for which we divide the SNR into around 700 distinct regions, resulting in maps of key physical quantities over its extent. Results. We find a strong peak of foreground absorption in the southwest quadrant, which in conjunction with high temperatures at the northeast rim creates the well-known strip of hard emission crossing Puppis A. Furthermore, using the observed distribution of ionization ages, we attempt to reconstruct the age of the shock in the individual regions. We find a quite recent shock interaction for the prominent northeast filament and ejecta knot, as well as for the outer edge of the bright eastern knot. Finally, elemental abundance maps reveal only a single clear enhancement of the plasma with ejecta material, consistent with a previously identified region, and no obvious ejecta enrichment in the remainder of the SNR. Within this region, we confirm the spatial separation of silicon-rich ejecta from those dominated by lighter elements.

astro-ph.HE↗
arXiv2011

GRAVITAS : General Relativistic Astrophysics VIa Timing And Spectroscopy: An ESA M3 mission proposal

GRAVITAS is an X-ray observatory, designed and optimised to address the ESA Cosmic Vision theme of "Matter under extreme conditions". It was submitted as a response to the call for M3 mission proposals. The concept centres around an X-ray telescope of unprecedented effective area, which will focus radiation emitted from close to the event horizon of black holes or the surface of neutron stars. To reveal the nature and behaviour of matter in the most extreme astrophysical environments, GRAVITAS targets a key feature in the X-ray spectra of compact objects: the iron Kalpha line at ~6.5 keV. The energy, profile, and variability of this emission line, and the properties of the surrounding continuum emission, shaped by General Relativity (GR) effects, provide a unique probe of gravity in its strong field limit. Among its prime targets are hundreds of supermassive black holes in bright Active Galactic Nuclei (AGN), which form the perfect laboratory to help understand the physical processes behind black hole growth. Accretion plays a fundamental role in the shaping of galaxies throughout cosmic time, via the process of feedback. Modest (~sub-arcmin) spatial resolution would deliver the necessary sensitivity to extend high quality X-ray spectroscopy of AGN to cosmologically-relevant distances. Closer to home, ultra-high count rate capabilities and sub-millisecond time resolution enable the study of GR effects and the equation of state of dense matter in the brightest X-ray binaries in our own Galaxy, using multiple probes, such as the broad iron line, the shape of the disk continuum emission, quasi-periodic oscillations, reverberation mapping, and X-ray burst oscillations. Despite its breakthrough capabilities, all enabling technologies for GRAVITAS are already in a high state of readiness. It is based on ultra light-weight X-ray optics and a focal plane detector using silicon technology.

astro-ph.HE↗
arXiv2010

Discovery of X-ray flaring activity in the Arches cluster

We present a study of the Arches cluster based on XMM-Newton observations performed over the past 8 years. Unexpectedly, we find that the X-ray emission associated with the cluster experienced a marked brightening in March/April 2007. We investigate the origin of both the X-ray continuum emission emanating from the star cluster and the flare. To study the time variability of the total X-ray flux, we stacked the PN and MOS data of observations performed within a time interval of a few days leading to the detection of the flaring episode. We then constructed two spectral datasets, one corresponding to the flare interval (March/April 2007) and another to the normal quiescent state of the source. The X-ray light curve of the Arches cluster shows, with high significance (8.6 sigma), a 70% increase in the X-ray emission in the March/April 2007 timeframe followed by a decline over the following year to the pre-flare level; the short-term duration of the flare is constrained to be longer than four days. The temperature and the line-of-sight column density inferred from the flare spectrum do not differ from those measured in the normal activity state of the cluster, suggesting that the flux enhancement is thermal in origin. We attribute the X-ray variability to in situ stellar activity: early-type stars may be responsible for the flare via wind collisions, whereas late-type stars may contribute by means of magnetic reconnection. These two possibilities are discussed.

astro-ph.HE↗
arXiv2010

eROSITA on SRG

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian Spektrum-Roentgen-Gamma (SRG) mission which is scheduled for launch in late 2012. eROSITA is fully approved and funded by the German Space Agency DLR and the Max-Planck-Society.The design driving science is the detection of 50-100 thousands Clusters of Galaxies up to redshift z~1.3 in order to study the large scale structure in the Universe and test cosmological models, especially Dark Energy. This will be accomplished by an all-sky survey lasting for four years plus a phase of pointed observations. eROSITA consists of seven Wolter-I telescope modules, each equipped with 54 Wolter-I shells having an outer diameter of 360 mm. This would provide and effective area at 1.5 keV of ~1500 cm2 and an on axis PSF HEW of 15" which would provide an effective angular resolution of 25"-30". In the focus of each mirror module, a fast frame-store pn-CCD will provide a field of view of 1deg in diameter for an active FOV of ~0.83 deg2. At the time of writing the instrument development is currently in phase C/D.

astro-ph.CO↗
arXiv2006

The X-ray Halo of GX5-1

Using Chandra observations we have measured the energy-resolved dust-scattered X-ray halo around the low-mass X-ray binary GX5-1, which shows signs of both singly- and multiply-scattered X-rays. We compared the observed X-ray halo at various energies to predictions from a range of dust models. These fits used both smoothly-distributed dust as well as dust in clumped clouds, with CO and 21 cm observations helping to determine the position of the clouds along the line of sight. We found that the BARE-GR-B model of Zubko, Dwek & Arendt (2004 generally led to the best results, although inadequacies in both the overall model and the data limit our conclusions. We also found that the composite dust models of Zubko, Dwek & Arendt (2004), especially the ``no carbon'' models, gave uniformly poor results. Although models using cloud positions and densities derived naively from CO and 21 cm data gave generally poor results, plausible adjustments to the distance of the largest cloud and the mass of a cloud in the expanding 3 kpc Arm lead to significantly improved fits. We suggest that combining X-ray halo, CO, and 21 cm observations will be a fruitful method to improve our understanding of both the gas and dust phases of the interstellar medium.

astro-ph↗
arXiv2003

XMM-Newton observations of Sagittarius A East

We present an analysis of a recent XMM-Newton observation of Sgr A East, a supernova remnant located close to the Galactic Centre. Very high quality X-ray spectra reveal many emission lines from highly ionized atoms consistent with a multi-temperature thin thermal plasma in ionization equilibrium. We use a two-temperature model to fit the spectra and derive temperatures of 1 keV and 4 keV. There is significant concentration of iron towards the centre of the X-ray source such that the iron abundance varies from ~4 times solar in the core down to ~0.5 solar in the outer regions, which contrasts with the rather uniform distribution of other metals such as sulfur, argon and calcium, which have abundances in the range 1--3. The derived total energy, mass, and the abundance pattern are consistent with a single supernova event, either of type-Ia or type-II origin, involving a relatively low-mass progenitor star. A weak 6.4-keV neutral iron fluorescence line is also detected, the illumination source most likely being Sgr A East itself. The morphology and spectral characteristics of Sgr A East show no clear linkage to putative past activity in Sgr A*.

astro-ph↗