arXiv subjects

Konrad Dennerl

Publications and source records attributed to Konrad Dennerl.

At least 19 recordsLinked to original sources

arXiv2026

Bayesian Modeling of NICER Cometary X-ray Spectra: A Legacy Survey of Solar-Wind Charge Exchange

We present a uniform, epoch-resolved analysis of soft X-ray observations of eight comets obtained with NICER, using Bayesian statistics to identify charge-exchange line components, measure relative ion fluxes, and infer nominal solar-wind freeze-in temperatures. The sample exhibits recurring spectral morphologies that fall into distinct families: carbon-dominated, intermediate, and nitrogen-/oxygen-dominated. Epoch-resolved flux ratios yield a robust separation between diagnostics: carbon-derived freeze-in temperatures cluster near T_freeze(C) about 1.4-1.7 MK, while nitrogen- and oxygen-derived diagnostics are systematically higher, typically T_freeze(N,O) about 2.0-2.3 MK. Short-timescale variability in inferred freeze-in conditions is common, indicating that instantaneous solar-wind charge-state fluctuations, rather than large changes in coma composition, dominate the spectral differences. We discuss instrumental and modeling limitations, demonstrate how our Bayesian fitting method mitigates degeneracies via physically motivated priors and Bayesian model selection, and recommend laboratory measurements and coordinated high-resolution X-ray observations to refine charge-exchange diagnostics and validate low-resolution inferences.

astro-ph.EP↗

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↗

arXiv2026

The average X-ray spectrum of the volume-complete M-, F-, G-, and K-type star sample within 10 pc of the Sun

F, G, K and M type stars are the most abundant stellar population in the Milky Way and are expected to contribute to its diffuse X-ray emission. Yet their intrinsic average X-ray spectrum remains poorly constrained due to their faint X-ray luminosities, leaving their collective role in the X-ray background of the Milky Way uncertain. We analysed the volume-complete sample of M- (M0--M6) and FGK-type stars within 10 pc of the Sun using data from eROSITA all-sky survey aboard the Spectrum-Roentgen-Gamma (SRG) mission (eRASS:4). Individual spectra were normalized by exposure and distance and stacked to produce representative averages. The distance-normalized emission measures yield an average X-ray luminosity of $(2.6 \pm0.1)\times 10^{27}$ erg/s for M-type stars, and $(15\pm3)\times 10^{27}$ erg/s for F, G and K-type stars in 0.2--2.0 keV. The average spectra could be well described by a sum of three and two thermal models. Fitted temperatures and abundances remain consistent across M-star subgroups, while early-M stars are surprisingly on average less luminous than mid/late-M types. These results offer new insights into the collective X-ray properties of nearby stars, and provide motivation to explore the link with the unresolved soft X-ray background of the Galaxy.

astro-ph.HE↗

arXiv2024

The SRG/eROSITA diffuse soft X-ray background. I. The local hot bubble in the western Galactic hemisphere

The SRG/eROSITA All-Sky Surveys (eRASSs) combine the advantages of complete sky coverage and the energy resolution provided by the charge couple device and offer the most holistic and detailed view of the diffuse soft X-ray background (SXRB) to date. The first eRASS (eRASS1) was completed at solar minimum, when solar wind charge exchange emission was minimal, providing the clearest view of the SXRB. We aim to extract spatial and spectral information from each constituent of the SXRB in the western Galactic hemisphere, focusing on the local hot bubble (LHB). We extracted and analysed eRASS1 spectra from almost all directions in the western Galactic hemisphere by dividing the sky into equal signal-to-noise bins. We fitted all bins with fixed spectral templates of known background constituents. We find the temperature of the LHB exhibits a north-south dichotomy at high latitudes ($|b|>30^{\circ}$), with the south being hotter, with a mean temperature at $kT=121.8\pm0.6\,$eV and the north at $kT=100.8\pm0.5\,$eV. At low latitudes, the LHB temperature increases towards the Galactic plane, especially towards the inner Galaxy. The LHB emission measure (${\rm EM_{LHB}}$) enhances approximately towards the Galactic poles. The ${\rm EM_{LHB}}$ map shows clear anti-correlation with the local dust column density. In particular, we found tunnels of dust cavities filled with hot plasma, potentially forming a wider network of hot interstellar medium. We also constructed a three-dimensional LHB model from ${\rm EM_{LHB}}$, assuming constant density. The average thermal pressure of the LHB is $P_{\rm thermal}/k=10100^{+1200}_{-1500}\,{\rm cm^{-3}\,K}$, a lower value than typical supernova remnants and wind-blown bubbles. This could be an indication of the LHB being open towards high Galactic latitudes.

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

Discovery of the Goat Horn complex: a $\sim 1000$ deg$^2$ diffuse X-ray source connected to radio loop XII

A dozen of patches of polarized radio emission spanning tens of degrees in the form of coherent and stationary loops are observed at radio frequencies across the sky. Their origin is usually associated to nearby shocks, possibly arising from close supernovae explosions. The origin of the radio Loop XII remains so far unknown. We report an anti-correlation of the radio polarized emission of loop XII with a large patch of soft X-ray emission found with SRG/eROSITA in excess of the background surface brightness, in the same region. The soft X-ray seemingly coherent patch in excess of the background emission, which we dub as the Goat Horn complex, extends over a remarkable area of $\sim 1000$ deg$^2$ and includes an arc-shaped enhancement potentially tracing a cold front. An anti-correlation of the X-ray intensity with the temperature of the plasma responsible for the X-ray emission is also observed. The X-ray bright arc seems to anticipate the radio loop XII by some degrees on the sky. This behavior can be recast in terms of a correlation between X-ray surface brightness and radio depolarization. We explore and discuss different possible scenarios for the source of the diffuse emission in the Goat Horn complex: a large supernova remnant; an outflow from active star formation regions in nearby Galactic spiral arms; a hot atmosphere around the Large Magellanic Cloud. In order to probe these scenarios further, a more detailed characterization on the velocity of the hot gas is required.

astro-ph.GA↗

arXiv2024

eROSITA narrowband maps at the energies of soft X-ray emission lines

[abridged] Hot plasma plays a crucial role in regulating the baryon cycle within the Milky Way, flowing from the energetic sources in the Galactic center and disc, to the corona and the halo. This hot plasma represents an important fraction of the Galactic baryons, plays a key role in galactic outflows and is an important ingredient in galaxy evolution models. Taking advantage of the Spectrum-Roentgen-Gamma (SRG))/eROSITA first all-sky survey (eRASS1), in this work, we aim to provide a panoramic view of the hot circumgalactic medium (CGM) of the Milky Way. Here we present the eROSITA eRASS1 half sky maps in narrow energy bands corresponding to the most prominent soft X-ray lines: OVII and OVIII, which allow us to constrain the distribution of the hot plasma within and surrounding the Milky Way. We corrected the maps by removing the expected contribution associated with the cosmic X-ray background, the time-variable solar wind charge exchange, and the local hot bubble. We applied corrections to mitigate the effect of absorption, therefore highlighting the emission from the CGM of the Milky Way. We use the line ratio of the oxygen lines as a proxy to constrain the temperature of the warm-hot CGM, and we define a pseudo-temperature $\mathcal{T}$ map. The map highlights how different regions are dominated by different thermal components. Towards the outer halo, the temperature distribution of the CGM on angular scales of 2-20 deg is consistent with being constant $\Delta \mathcal{T} / \langle \mathcal{T}\rangle \leq 4\%$, with a marginal detection of $\Delta \mathcal{T} / \langle \mathcal{T}\rangle = 2.7 \% \pm 0.2\%$ (statistical) $\pm 0.6\%$ (systematic) in the southern hemisphere. Instead, significant variations $\sim 12\%$ are observed on many tens of degrees scales when comparing the northern and southern hemispheres.

astro-ph.GA↗

arXiv2023

Revolutionary Solar System Science Enabled by the Line Emission Mapper X-ray Probe

The Line Emission Mapper's (LEM's) exquisite spectral resolution and effective area will open new research domains in Astrophysics, Planetary Science and Heliophysics. LEM will provide step-change capabilities for the fluorescence, solar wind charge exchange (SWCX) and auroral precipitation processes that dominate X-ray emissions in our Solar System. The observatory will enable novel X-ray measurements of historically inaccessible line species, thermal broadening, characteristic line ratios and Doppler shifts - a universally valuable new astrophysics diagnostic toolkit. These measurements will identify the underlying compositions, conditions and physical processes from km-scale ultra-cold comets to the MK solar wind in the heliopause at 120 AU. Here, we focus on the paradigm-shifts LEM will provide for understanding the nature of the interaction between a star and its planets, especially the fundamental processes that govern the transfer of mass and energy within our Solar System, and the distribution of elements throughout the heliosphere. In this White Paper we show how LEM will enable a treasure trove of new scientific contributions that directly address key questions from the National Academies' 2023-2032 Planetary Science and 2013-2022 Heliophysics Decadal Strategies. The topics we highlight include: 1. The richest global trace element maps of the Lunar Surface ever produced; insights that address Solar System and planetary formation, and provide invaluable context ahead of Artemis and the Lunar Gateway. 2. Global maps of our Heliosphere through Solar Wind Charge Exchange (SWCX) that trace the interstellar neutral distributions in interplanetary space and measure system-wide solar wind ion abundances and velocities; a key new understanding of our local astrosphere and a synergistic complement to NASA IMAP observations of heliospheric interactions...

astro-ph.IM↗

arXiv2023

SRG/eROSITA X-ray shadowing study of giant molecular clouds

SRG/eROSITA is situated in a halo orbit around L2 where the highly variable solar wind charge exchange (SWCX) emission from Earth's magnetosheath is expected to be negligible. The soft X-ray foreground emissions from the local hot bubble (LHB) and the remaining heliospheric SWCX emissions could be studied in unprecedented detail with eROSITA All-Sky Survey (eRASS) data in a 6-month cadence and better spectral resolution than ROSAT. We aim to use eRASS data of the sight lines towards three giant molecular clouds away from the Galactic plane to isolate and study the soft X-ray diffuse foreground emission. These X-ray shadows will serve as calibration baselines for the future three-dimensional structural study of the LHB. We conducted spectral analysis on the diffuse X-ray spectra of these clouds from the first four eRASSs to estimate and separate the heliospheric SWCX contribution from the LHB emission. We find the density of the LHB to be independent of the sight line with $n_e \sim 4 \times 10^{-3}\,$cm$^{-3}$, but not the temperature. We report a lower temperature of $kT_{\mathrm{LHB}}=0.084\pm0.004\,$keV towards Chamaeleon$~$II & III (Cha$~$II & III) than Ophiuchus (Oph) and Corona Australis (CrA), in which we measured $0.102\pm0.006$ and $0.112\pm0.009\,$keV, respectively. We measured the emission measure of the LHB to be $\sim 2\times10^{-3}\,$cm$^{-6}\,$pc at medium Galactic latitudes ($|b| \sim 20^{\circ}$). A monotonic increase in the SWCX contribution has been observed since the start of 2020, coincidental with the beginning of solar cycle 25. For Oph, SWCX has dominated the LHB in the $0.3$-$0.7\,$keV band intensity since eRASS2. We observed lower SWCX contributions in Cha$~$II & III and CrA, consistent with the expected decreasing solar wind ion density at high heliographic latitudes.

astro-ph.GA↗

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 $μ$G and 16 $μ$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

X-ray detection of a nova in the fireball phase

Novae are caused by runaway thermonuclear burning in the hydrogen-rich envelopes of accreting white dwarfs, which results in the envelope to expand rapidly and to eject most of its mass. For more than 30 years, nova theory has predicted the existence of a "fireball" phase following directly the runaway fusion, which should be observable as a short, bright, and soft X-ray flash before the nova becomes visible in the optical. Here we present the unequivocal detection of an extremely bright and very soft X-ray flash of the classical Galactic nova YZ Reticuli 11 hours prior to its 9 mag optical brightening. No X-ray source was detected 4 hours before and after the event, constraining the duration of the flash to shorter than 8 hours. In agreement with theoretical predictions, the source's spectral shape is consistent with a black body of $3.27^{+0.11}_{-0.33}\times 10^5$ K ($28.2^{+0.9}_{-2.8}$ eV), or a white dwarf atmosphere, radiating at the Eddington luminosity, with a photosphere that is only slightly larger than a typical white dwarf. This detection of the expanding white dwarf photosphere before the ejection of the envelope provides the last link of the predicted photospheric lightcurve evolution and opens a new window to measure the total nova energetics.

astro-ph.HE↗

arXiv2022

EROSITA study of the 47~Tucanae globular cluster

Aims. We present the results of the analysis of five observations of the globular cluster 47 Tucanae (47 Tuc) with eROSITA (extended Roentgen Survey with an Imaging Telescope Array) on board Spektrum-Roentgen-Gamma (Spektr-RG, SRG). The aim of the work is the study of the X-ray population in the field of one of the most massive globular clusters in our Milky Way. We focused on the classification of point-like sources in the field of 47 Tuc. The unresolved dense core of 47 Tuc (1$'$.7 radius) and also the sources, which show extended emission are excluded in this study. Methods. We applied different methods of X-ray spectral and timing analysis together with multi wavelength studies for the classification of the X-rays sources in the field of 47 Tuc. Results. We detected 888 point-like sources in the energy range of 0.2-5.0 keV. We identified 126 background AGNs and 25 foreground stars. One of the foreground stars is classified as a variable M dwarf. We also classified 14 X-ray sources as members of 47 Tuc, including 1 symbiotic stars, 2 quiescent low mass X-ray binaries, and 4 cataclysmic variable. There are also 5 X-ray sources, which can either be a cataclysmic variable or a contact binary, and also 1 X-ray sources which can be an active binary (Type RS CVn). We identified one X-ray binary, which belongs to the Small Magellanic Cloud. Moreover, we calculated the X-ray luminosity function of 47 Tuc. No significant population that seems to belong to the globular cluster has been observed in the energy range of 0.5-2.0 keV using eROSITA observations.

astro-ph.HE↗

arXiv2021

First studies of the diffuse X-ray emission in the Large Magellanic Cloud with eROSITA

In the first months after the launch in July 2019, eROSITA onboard Spektr-RG (SRG) performed long-exposure observations in the regions around SN 1987A and SNR N132D in the Large Magellanic Cloud (LMC). We analyse the distribution and the spectrum of the diffuse X-ray emission in the observed fields to determine the physical properties of the hot phase of the interstellar medium (ISM). The eROSITA data are complemented by newly derived column density maps for the Milky Way and the LMC, 888 MHz radio continuum map from the Australian Square Kilometer Array Pathfinder (ASKAP), and optical images of the Magellanic Cloud Emission Line Survey (MCELS). We detect significant emission from thermal plasma with kT=0.2 keV in all the regions. There is also an additional higher-temperature emission component from a plasma with kT = 0.7 keV. In addition, non-thermal X-ray emission is significantly detected in the superbubble 30 Dor C. The absorbing column density NH in the LMC derived from the analysis of the X-ray spectra taken with eROSITA is consistent with the NH obtained from the emission of the cold medium over the entire area. Neon abundance is enhanced in the regions in and around 30 Dor and SN 1987A, indicating that the ISM has been chemically enriched by the young stellar population. Emission from the stellar cluster RMC 136 and the Wolf-Rayet stars RMC 139 and RMC 140 is best modelled with a high-temperature (kT>1 keV) non-equilibrium ionisation plasma emission and a non-thermal component with a photon index of Γ =1.3. In addition, the optical SNR candidate J0529-7004 is also detected with eROSITA and we thus confirm the source as an SNR.

astro-ph.HE↗

arXiv2021

Phase-resolved X-ray spectroscopy of PSR B0656+14 with SRG/eROSITA and XMM-Newton

(abridged version) We present a detailed spectroscopic and timing analysis of X-ray observations of the bright radio-to-gamma-ray emitting pulsar PSR B0656+14, which were obtained simultaneously with eROSITA and XMM-Newton during the Calibration and Performance Verification phase of the Spektrum-Roentgen-Gamma mission (SRG) for 100 ks. Using XMM-Newton and NICER we firstly established an X-ray ephemeris for the time interval 2015 to 2020, which connects all X-ray observations in this period without cycle count alias and phase shifts. The mean eROSITA spectrum clearly reveals an absorption feature originating from the star at 570 eV with a Gaussian sigma of about 70 eV, tentatively identified earlier in a long XMM-Newton observation (Arumugasamy et al. 2018). A second absorption feature, described here as an absorption edge, occurs at 260-265 eV. It could be of atmospheric or of instrumental origin. These absorption features are superposed on various emission components, phenomenologically described as the sum of hot (120 eV) and cold (65 eV) blackbody components, both of photospheric origin, and a power-law with photon index Gamma=2. The phase-resolved spectroscopy reveals that the Gaussian absorption line at 570 eV is clearly present throughout ~60% of the spin cycle. The visibility of the line strength coincides in phase with the maximum flux of the hot blackbody. We also present three families of model atmospheres: a magnetised atmosphere, a condensed surface, and a mixed model, which were applied to the mean observed spectrum and whose continuum fit the observed data well. The atmosphere model, however, predicts too short distances. For the mixed model, the Gaussian absorption may be interpreted as proton cyclotron absorption in a field as high as 10^14 G, which is significantly higher than that derived from the moderate observed spin-down.

astro-ph.HE↗

arXiv2019

X-rays Studies of the Solar System

X-ray observatories contribute fundamental advances in Solar System studies by probing Sun-object interactions, developing planet and satellite surface composition maps, probing global magnetospheric dynamics, and tracking astrochemical reactions. Despite these crucial results, the technological limitations of current X-ray instruments hinder the overall scope and impact for broader scientific application of X-ray observations both now and in the coming decade. Implementation of modern advances in X-ray optics will provide improvements in effective area, spatial resolution, and spectral resolution for future instruments. These improvements will usher in a truly transformative era of Solar System science through the study of X-ray emission.

astro-ph.HE↗

arXiv2016

Chandra Observations of Comets C/2012 S1 (ISON) and C/2011 L4 (PanSTARRS)

We present our results on the Chandra X-ray Observatory Advanced CCD Imaging Spectrometer (ACIS) observations of the bright Oort Cloud comets C/2012 S1 (ISON) and C/2011 L4 (PanSTARRS). ISON was observed between 2013 October 31-November 06 during variable speed solar wind (SW), and PanSTARRS was observed between 2013 April 17-23 during fast SW. ISON produced an extended parabolic X-ray morphology consistent with a collisionally thick coma, while PanSTARRS demonstrated only a diffuse X-ray-emitting region. We consider these emissions to be from charge exchange (CX) and model each comet's emission spectrum from first principles accordingly. Our model agrees with the observational spectra and also generates composition ratios for heavy, highly charged SW ions interacting with the cometary atmosphere. We compare our derived SW ion compositions to observational data and find a strong agreement between them. These results further demonstrate the utility of CX emissions as a remote diagnostics tool of both astrophysical plasma interaction and SW composition. In addition, we observe potential soft X-ray emissions via ACIS around 0.2 keV from both comets that are correlated in intensity to the hard X-ray emissions between 0.4-1.0 keV. We fit our CX model to these emissions, but our lack of a unique solution at low energies makes it impossible to conclude if they are cometary CX in origin. We lastly discuss probable emission mechanism sources for the soft X-rays and explore new opportunities these findings present in understanding cometary emission processes via Chandra.

astro-ph.HE↗

arXiv2013

On the nature of dark matter in the Coma Cluster

Recent precise observations of the 2.7 K CMB by the Planck mission toward the Coma cluster are not in agreement with X-ray measurements. To reconcile both types of measuring techniques we suggest that unstable dark matter is the cause of this mismatch. Decaying dark matter, which gravitationally dominates the galaxy cluster, can affect the estimated hot plasma content, which is then missing in the measured SZ effect from exactly the same place in the sky. The model independent lifetime of dark matter decaying entirely to X-rays is estimated to be about 6x10^{24} sec; this lifetime scales down with the fraction of the radiatively decaying dark matter. In addition, it is shown that the potential of such dark matter investigations in space is superior to the largest volume Earth-bound dark matter decay searches. Other clusters might provide additional evidence for or against this suggestion.

astro-ph.CO↗

arXiv2013

The Hot and Energetic Universe: A White Paper presenting the science theme motivating the Athena+ mission

This White Paper, submitted to the recent ESA call for science themes to define its future large missions, advocates the need for a transformational leap in our understanding of two key questions in astrophysics: 1) How does ordinary matter assemble into the large scale structures that we see today? 2) How do black holes grow and shape the Universe? Hot gas in clusters, groups and the intergalactic medium dominates the baryonic content of the local Universe. To understand the astrophysical processes responsible for the formation and assembly of these large structures, it is necessary to measure their physical properties and evolution. This requires spatially resolved X-ray spectroscopy with a factor 10 increase in both telescope throughput and spatial resolving power compared to currently planned facilities. Feedback from supermassive black holes is an essential ingredient in this process and in most galaxy evolution models, but it is not well understood. X-ray observations can uniquely reveal the mechanisms launching winds close to black holes and determine the coupling of the energy and matter flows on larger scales. Due to the effects of feedback, a complete understanding of galaxy evolution requires knowledge of the obscured growth of supermassive black holes through cosmic time, out to the redshifts where the first galaxies form. X-ray emission is the most reliable way to reveal accreting black holes, but deep survey speed must improve by a factor ~100 over current facilities to perform a full census into the early Universe. The Advanced Telescope for High Energy Astrophysics (Athena+) mission provides the necessary performance (e.g. angular resolution, spectral resolution, survey grasp) to address these questions and revolutionize our understanding of the Hot and Energetic Universe. These capabilities will also provide a powerful observatory to be used in all areas of astrophysics.

astro-ph.HE↗