J. Nevalainen

Tartu Observatory

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Massimiliano Bonamente

University of Alabama in Huntsville

J. S. Kaastra

SRON Netherlands Institute for Space Research

A. Finoguenov

University of Helsinki

T. H. Reiprich

University of Bonn

P. Heinämäki

University of Turku

Ulrich Schiefer

University of Tübingen

O. Vilhu

University of Helsinki

Jens Paetzold

Technical University of Darmstadt

M. Guainazzi

European Space Research and Technology Centre

S. Molendi

Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano

Cooperative Institutions

Centre National de la Recherche Scientifique

187

National Institute for Astrophysics

185

Max Planck Society

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Université Paris Cité

Center for Astrophysics Harvard & Smithsonian

Institute for Space Astrophysics and Planetology

Max Planck Institute for Extraterrestrial Physics

Agenzia Spaziale Italiana

SRON Netherlands Institute for Space Research

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Summary of the 12th IACHEC Meeting

arXiv (Cornell University) (2017)

Karl Förster Catherine E. Grant M. Guainazzi V. Kashyap Herman L. Marshall

We summarize the outcome of the 12th meeting of the International Astronomical Consortium for High Energy Calibration (IACHEC), held at the UCLA conference center in Lake Arrowhead (California) in March 2017. 56 scientists directly involved in the calibration of operational and future high-energy missions gathered during 3.5 days to discuss the status of the X-ray payload inter-calibration, as well as possible ways to improve it. The Thermal Supernovas Remnant (SNR) Working Group presented a recently published paper on 1E0102.2-7219 as a calibration standard in the 0.5-1.0 keV band. A new method to measure the high-energy spectrum of the Crab Nebula and pulsar with NuSTAR without using its optics may yield a new absolute flux standard in the 3-7 keV band. A new ACIS contamination model - released with CALDB version 4.7.3 - leads to a significant improvement in modeling the spectral, spatial, and temporal properties of the contaminant. The first calibration results of the scientific payload on board Hitomi confirm the excellent performance of the instruments before the spacecraft operation problems leading to its loss. Finally, the meeting discussed extensively a novel statistic approach to formally identify in which direction the effective areas of different instruments would need to be changed to bring them into concordance. This method could inform future further calibration efforts.

Payload (computing)

Crab Nebula

Acis

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Age-Corrected Normative Data for the Entire (80 Degree) Visual Field, Assessed With a New Fast Thresholding Estimation (GATE)

Ulrich Schiefer Susanne Frick J. Nevalainen J. Grobbel E. Krapp

Degree (music)

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Two-phase Spectrum of the Black Hole Candidate 1E1740.7-2942

Physica Scripta (1998)

J. Nevalainen O. Vilhu Juri Poutanen M. Gilfanov M. L. García-Vargas

Combined ASCA and SIGMA data of 1E1740.7-2942 during its standard state (September 1993 and 1994) were successfully fitted with a two-phase model ISM iterative scattering method) [1]. The classical cold accretion disk does not extend up to the innermost stable orbit, but is truncated at ~ 30GM/c2. A hot inner disk has electron temperature Te ≈ 60 keV and radial Thomson optical depth τ ≈ 2.4. The cold disk radiates ≈ 40% of the total luminosity with ≈ 0.04Edd of 10M⊙.

Thomson scattering

Accretion disc

Orbit (dynamics)

Black hole (networking)

10.1088/0031-8949/1998/t77/025

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The Large Observatory for X-ray Timing (LOFT)

Experimental Astronomy (2011)

M. Feroci L. Stella M. van der Klis T. J. L. Courvoisier M. Hernanz

Spectral resolution

10.1007/s10686-011-9237-2

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Citations (195)

XMM-Newton and INTEGRAL analysis of the Ophiuchus cluster of galaxies

Astronomy and Astrophysics (2009)

J. Nevalainen D. Eckert J. S. Kaastra Massimiliano Bonamente K. Kettula

Aims. We investigated the non-thermal hard X-ray emission in the Ophiuchus cluster of galaxies. Our aim is to characterise the physical properties of the non-thermal component and its interaction with the cosmic microwave background.Methods. We performed spatially resolved spectroscopy and imaging using XMM-Newton data to model the thermal emission. Combining this with INTEGRAL ISGRI data, we modelled the 0.6-140 keV band total emission in the central 7 arcmin region.Results. The models that best describe both PN and ISGRI data contain a power-law component with a photon index in a range 2.2-2.5. This component produces ~10% of the total flux in the 1-10 keV band. The pressure of the non-thermal electrons is ~1% of that of the thermal electrons. Our results support the scenario whereby a relativistic electron population, which produces the recently detected radio mini-halo in Ophiuchus, also produces the hard X-rays via inverse compton scattering of the CMB photons. The best-fit models imply a differential momentum spectrum of the relativistic electrons with a slope of 3.4-4.0 and a magnetic field strength μG. The lack of evidence for a recent major merger in the Ophiuchus centre allows the possibility that the relativistic electrons are produced by turbulence or hadronic collisions.

Ophiuchus

Radio halo

Coma Cluster

10.1051/0004-6361/200912542

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Citations (16)

The Soft X‐Ray Emission in a Large Sample of Galaxy Clusters with theROSATPosition Sensitive Proportional Counter

The Astrophysical Journal (2002)

Massimiliano Bonamente Richard Lieu Marshall K. Joy J. Nevalainen

The study of soft X-ray emission of 38 X-ray selected galaxy clusters observed by ROSAT PSPC indicates that the soft excess phenomenon may be a common occurrence in galaxy clusters. Excess soft X-ray radiation, above the contribution from the hot intra-cluster medium, is evident in a large fraction of sources, and is clearly detected with large statistical significance in the deepest observations. The investigation relies on new, high resolution 21 cm HI observations. The sample selection also features analysis of infra-red images, to further ensure reliability of results with respect to the characteristics of Galactic absorption. The possibility of background or calibration effects as cause of the excess emission is likewise investigated; a detailed analysis of the distribution of the excess emission with respect to detector position and Galactic HI column density shows that the excess emission is a genuine celestial phenomenon. We find evidence for a preferential distribution of the soft excess emission at distances larger than ~150-200 kpc from the centers of clusters; this behavior may be naturally explained in the context of a non-thermal Inverse-Compton scenario. Alternatively, we propose that the phenomenon may be caused by thermal emission of very large-scale `warm' filaments seen in recent hydrodynamic simulations. This new interpretation relieves the very demanding requirements of either the traditional intra-cluster `warm' gas and the non-thermal scenarios. We also investigate the possibility of the soft excess originating from unresolved, X-ray faint cluster galaxies.

ROSAT

Local Bubble

10.1086/341806

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Citations (51)

Nonthermal Phenomena in Clusters of Galaxies

Space Science Reviews (2008)

Yoel Rephaeli J. Nevalainen T. Ohashi A. M. Bykov

Intracluster medium

10.1007/s11214-008-9314-7

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Citations (54)

Cosmic gas highways in C-EAGLE simulations

Astronomy and Astrophysics (2023)

I. Vurm J. Nevalainen Sungwook E. Hong Yannick M. Bahé Claudio Dalla Vecchia

Context. A substantial fraction of cosmic baryons is expected to hide in the form of diffuse warm-hot intergalactic medium (WHIM) at X-ray temperatures ( T = 10 5 − 10 7 K). Due to the expected low density of WHIM, it has been very difficult to detect so far. A statistically significant sample of credible detections of the WHIM phase might help solve the problem of the missing cosmic baryons. While the majority of cosmic gas is approximately at rest inside the filaments of the Cosmic Web, the fraction of gas located close to galaxy clusters is falling towards them with substantial velocities. The infalling gas is influenced by the increasing density in the cluster vicinity and eventually undergoes a termination shock, which may boost its X-ray signal. Thus, the cluster outskirts are potential locations for improved detectability of the missing baryons. Aims. The primary goal of this work is to identify optimal locations of the enhanced X-ray emission and absorption, arising from the interaction of infalling filamentary gas with cluster material. Our further goal is to improve our understanding of the various physical processes affecting WHIM as it falls towards clusters of galaxies along the cosmic filaments. We aim to utilise this information for planning future X-ray observations of WHIM in cluster outskirts. Methods. We applied the DisPerSE filament finder to the galaxy distribution in the surroundings of a single Coma-like ( M 200 ∼ 10 15.4 M ⊙ ) simulated C-EAGLE cluster of galaxies. We characterised the distribution of the thermodynamic properties of the gas in such filaments and provided a physical interpretation for the results. This analysis serves as a proof of method to be applied to the full C-EAGLE sample in a future work. Results. We captured a large fraction (∼50%) of the hot ( T > 10 5.5 K) gas falling towards the cluster in the detected filaments in the cluster outskirts. The gas in the filaments is in approximate free fall all the way down to the radial distance of ∼2 r 200 from the cluster. At smaller radii, the filament gas begins to slow down due to the increasing pressure of the ambient gas; approximately half of the filament gas nevertheless penetrates into the cluster before being decelerated. The deceleration is accompanied by the conversion of gas bulk kinetic energy into heat. As a result, the density and temperature of the gas in the filaments increase from the general Cosmic Web level of ρ ∼ 10 ρ av (where ρ av is the cosmic mean baryon density) and T = 10 5 − 10 6 K at r ∼ 4 r 200 towards ρ ∼ 100 ρ av and T = 10 7 − 10 8 K at the virial boundary of the very massive cluster studied in this paper. Conclusions. The detection of the cosmic filaments of galaxies around clusters may provide a practical observational avenue for locating the densest and hottest phase of the missing baryons.

Coma Cluster

10.1051/0004-6361/202243904

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Discovery of Galactic OIV and OV X-ray absorption due to transition temperature gas in the PKS 2155-304 spectrum

xru (2017)

J. Nevalainen

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Summary of the 2014 IACHEC Meeting

D. N. Burrows F. Gastaldello Catherine E. Grant M. Guainazzi Kristin K. Madsen

We present the main results of the 9th meeting of the International Astronomical Consortium for High Energy Calibration (IACHEC), held in Warrenton (Virginia) in May 2014. Over 50 scientists directly involved in the calibration of operational and future high-energy missions gathered during 3.5 days to discuss the status of the X-ray payloads inter-calibration, as well as possible ways to improve it. Sect.2 of this Report summarises our current understanding of the energy-dependent inter-calibration status.

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Citations (2)