arXiv subjects

Gerrit Schellenberger

Publications and source records attributed to Gerrit Schellenberger.

At least 19 recordsLinked to original sources

arXiv2026

High-statistics simulations of NewAthena WFI background using Geant4

The observation of hot gas structures is one science goal of the Wide Field Imager (WFI) on ESA's NewAthena X-ray observatory. Because the measurement of these faint diffuse sources is limited by background from cosmic ray particle interactions within the instrument, understanding and reducing this background is critical. To this end, we employ a two-pronged approach, performing high-fidelity Geant4 simulations on both detailed, realistic geometry models as well as complementary simple geometry models. The former can reveal subtle sensitivities of background to details of the instrument design. The latter allows for fast iteration, useful in guiding and understanding the larger simulations. We show how we leverage High Performance Computing (HPC) resources to achieve simultaneously high throughput and fast time to result. We discuss our recent results, which are applicable not only to WFI, but also other X-ray missions.

astro-ph.IM↗

arXiv2026

Resolving the temporal evolution of M87 jet with $\lesssim0.1$-arcsec Chandra observations

We present a 13-year Chandra/HRC-I study of the M87 jet, using point-spread-function deconvolution to achieve unprecedented sub-arcsecond X-ray resolution of its kiloparsec-scale structure and temporal evolution. The deconvolved images reveal previously blended structures within the jet, including two components in HST-1 and complex morphology in downstream knots. Flux measurements reveal a global decrease in X-ray emission across the jet of up to 84 %, consistent with synchrotron cooling. Modeling the fading yields minimum magnetic field strengths of ~324-1006 $\mu$G for HST-1 and ~41-115 $\mu$G for knot A. Consistent with synchrotron cooling, multi-wavelength comparisons with ALMA, JWST, and HST show that the principal X-ray structures closely match the jet width and knot locations observed at lower energies, while the X-ray emission is generally shifted upstream. Proper motion measurements show that jet features exhibit both quasi-stationary and superluminal apparent motions, reaching up to 4.8 $c$ for HST-1, and also demonstrate that unresolved component blending can substantially bias inferred velocities. These results demonstrate the unique capability of high-resolution Chandra X-ray imaging over long temporal baselines to resolve the evolving substructure of relativistic jets and to probe the particle acceleration and energy dissipation processes that shape their dynamics.

astro-ph.HE↗

arXiv2026

AGN Fueling and Radio Jet Evolution in the Galaxy Group NGC 5044 revealed by VLBA HI Absorption and Proper-Motion Radio Observations

The role of cooling gas in triggering active galactic nucleus (AGN) feedback in the centers of galaxy groups and clusters remains a key open question. NGC 5044, the X-ray brightest galaxy group, hosts the largest known reservoir of molecular gas among cool-core groups and exhibits multiple AGN outbursts, making it an ideal system to study AGN feeding. We present new multi-frequency Very Long Baseline Array (VLBA) observations of NGC 5044 at 1.4 GHz, 4.9 GHz, and 8.4 GHz, combining continuum imaging with HI spectroscopy. At 1.4 GHz, we recovered the previously known symmetric northeast-southwest jets extending for 5.5 pc each, along with evidence for previously undetected, more extended faint emission aligned with the older, kpc-scale outbursts. Comparison of 4.9 GHz and 8.4 GHz data from 2020 and 2024 reveals clear outward proper motion of jet components, yielding an average expansion speed of $(0.10\pm0.02)\,c$ and implying a dynamical age of $\sim$180 yr for the ejection of the parsec-scale jet components. The jet width profile suggests a transition from parabolic to conical collimation at a few $\times 10^{4}$ Schwarzschild radii. We detect a narrow, redshifted HI absorption line at $+264\,\mathrm{km\,s^{-1}}$ against the VLBA core, tracing a compact, cold atomic cloud within $\sim$10-20 pc of the AGN. The close velocity correspondence with previously detected CO and HI absorption features in ALMA and MeerKAT data, respectively, demonstrates that cold atomic and molecular gas coexists in infalling clouds at parsec scales. Overall, these results provide an unprecedented high angular resolution view of AGN cycling, jet growth, and feeding in a galaxy group environment.

astro-ph.GA↗

arXiv2026

HST view of NGC 5044: Constraints on Filament Widths, Magnetic Support, Multiphase Structure, and Comparison with Cluster Environments

We present new Hubble Space Telescope (HST) imaging of ionised filaments in the brightest group galaxy NGC 5044. These filaments extend several kiloparsecs and have widths of $\sim$50--120 pc, with some as narrow as those in cluster cores and others broader, reflecting the lower confining pressure in groups. Filament width ($W$) scales with ambient pressure ($P$) as $W \propto P^{-0.4}$. Combining HST, ALMA, and MUSE data, we measure column densities and magnetic field strengths. Equipartition fields decline from $\sim$40 $\mu$G at the centre to $\sim$20 $\mu$G at 5 kpc, about 2--3 times weaker than in clusters. Dynamical stability requires stronger radial fields ($\sim$10$^2$ $\mu$G), consistent with simulations and magnetic draping, though such high values exceed Faraday Rotation Measure limits. Turbulence and cosmic rays also contribute support. Group and cluster filaments are stable against gravitational collapse, and ultraviolet imaging reveals no star formation in NGC 5044 ($<$10$^{-3}$ M$_\odot$ yr$^{-1}$). NGC 5044 hosts an ionised gas core within its Bondi radius with $n_e \propto r^{-1}$ and filling factor $f \gtrsim 3 \times 10^{-3}$, that is connected to the extended filaments, suggesting a channel for gas inflow toward the black hole. Group and cluster filaments likely share a common origin, with magnetic fields and AGN feedback preserving their structure. Ambient pressure and dust survival regulate molecular gas formation. Lower-pressure groups favour broader, more diffuse filaments with sporadic molecular clumps and weaker dust shielding, whereas higher-pressure clusters host narrower strands with stronger molecular-ionised gas alignment. We predict that (i) filament width scales with ambient pressure, (ii) filament-coincident Faraday rotation structures emerge at $\leq 0.1$ kpc resolution, and (iii) molecular/ionised gas co-spatiality is weaker in groups than in clusters.

astro-ph.GA↗

arXiv2026

An X-ray-Emitting Proto-Cluster at $z\approx5.7$ Reveals Rapid Structure Growth

Galaxy clusters are the most massive gravitationally bound structures in the universe and serve as tracers of the assembly of large-scale structure. Studying their progenitors, proto-clusters, sheds light on the earliest stages of cluster formation. Yet, detecting proto-clusters is demanding: their member galaxies are loosely bound and the emerging hot intracluster medium (ICM) may only be in the initial stages of virialization. Recent JWST observations located several proto-cluster candidates by identifying overdensities of $z\gtrsim5$ galaxies. However, none of these candidates was detected by X-ray observations, which offer a powerful way to unveil the hot ICM. Here, we report the combined Chandra and JWST detection of a proto-cluster, JADES-ID1, at $z\approx5.68$, merely one billion years after the Big Bang. We measure a bolometric X-ray luminosity of $L_{\rm bol} = (1.5^{+0.5}_{-0.6}) \times10^{44} \ \rm{erg \ s^{-1}}$ and infer a total gravitating mass of $M_{500}= (1.8^{+0.6}_{-0.7}) \times 10^{13} \ \rm{M_{\odot}}$, making this system a progenitor of today's most massive galaxy clusters. The detection of extended, shock-heated gas indicates that substantial ICM heating can occur in massive halos as early as $z\approx5.7$. In addition, given the limited survey volume, the discovery of such a massive cluster is statistically unlikely, implying that the formation of the large-scale structure must have occurred more rapidly in some regions of the early universe than standard cosmological models predict.

astro-ph.CO↗

arXiv2025

Cross Calibration of Galaxy Cluster Temperatures Measured with NuSTAR, XMM-Newton, and Chandra

The use of galaxy clusters to constrain cosmology is limited in part due to uncertainties in derived cluster masses, which often depend on the gas temperature. Unfortunately, there exists a longstanding discrepancy in temperature measurements of the same galaxy clusters made by the two most sensitive X-ray observatories, Chandra and XMM-Newton. The NuSTAR X-ray Observatory's greater sensitivity to the exponential turnover in the bremsstrahlung continuum allows for more precise and potentially more accurate galaxy cluster temperature estimates, especially given its unique ability to independently calibrate its optics in orbit. We present new NuSTAR spectra of 10 relaxed clusters ($5~\mathrm{keV} < kT < 10~\mathrm{keV}$), extracted from identical regions as previous spectra from Chandra and XMM-Newton. The 3--20~keV spectra are well fit by single temperature models, and fits done in narrower bandpasses provide no clear evidence in support of the existence of multi temperature gas. We find NuSTAR temperatures are typically $\sim 15\%$ higher than XMM-Newton temperatures. In contrast, good agreement is found between NuSTAR and Chandra temperatures for clusters with $kT \lesssim 7~\mathrm{keV}$, with Chandra measurements exceeding NuSTAR's in hotter systems. When more clusters are included, the trend is reinforced and can be extended to higher temperatures. A generic increase to Chandra's $E > 2~\mathrm{keV}$ effective area ($\sim 5\%$ at 5~keV) is found to explain the trend reasonably well. These results demonstrate the potential for NuSTAR data to address the two-decade-old temperature discrepancy between Chandra and XMM-Newton.

astro-ph.HE↗

arXiv2025

Multiphase gas offsets in the atmospheres of central galaxies and their consequences for SMBH activation I. The hot and warm ionized gas phases

We investigate the spatial relationships between multi-phase gas components and supermassive black hole (SMBH) activity in a sample of 25 cool core galaxy groups and clusters. Using high angular resolution observations from \textit{Chandra}, VLT/MUSE, and VLBA, we robustly locate the position, respectively, of the X-ray peak of the intracluster medium (ICM), of the H$\alpha$ peak of the warm ionized gas, and of the SMBH radio core on parsec scales. We identify spatial offsets between the X-ray peak of the hot gas and the SMBH in 80% of the systems, with an average displacement of $\langle\Delta^{\text{SMBH}}_{\text{X-ray}}\rangle = 4.8$ kpc (dispersion of $3.8$ kpc). In contrast, the peak of warm ionized gas traced by H$\alpha$ exhibits much smaller offsets ($\langle\Delta^{\text{SMBH}}_{\text{H}\alpha}\rangle = 0.6$ kpc; dispersion of $1.4$ kpc) and a lower incidence of displacement (15%). Our findings suggest that hot gas sloshing primarily drives the observed spatial offsets, with AGN-driven uplift contributing in some systems.Importantly, systems with H$\alpha$ - SMBH offsets of $\geq$1 kpc uniformly lack detectable radio cores on VLBA scales, with upper limits on the 5~GHz power of $P_{5\,\text{GHz}} \leq 10^{21-22}$ W Hz$^{-1}$, while those without such offsets exhibit radio powerful AGN with pc-scale radio emission up to $P_{5\,\text{GHz}} \sim 10^{24-25}$ W Hz$^{-1}$. This correlation indicates that centrally concentrated warm gas is critical for sustaining radio-loud SMBH activity, possibly supporting scenarios of cold-mode accretion. Overall, our results highlight the importance of high-angular-resolution, multi-wavelength observations for understanding the interplay between multiphase gas cooling and AGN fueling in central galaxies.

astro-ph.GA↗

arXiv2025

JVLA and VLBA study of the merging cool core CHIPS 1911+4455 at z~0.5: radio emission from an infant AGN and from a rapidly star-forming BCG

Recent studies of galaxy clusters found peculiar cases at the boundary between non-cool core and cool core systems. While unusual, these objects can help us understand the evolution of the most massive clusters. We investigated the role of active galactic nucleus (AGN) feedback in the starburst brightest cluster galaxy (BCG) of the merging cool core cluster CHIPS 1911+4455 (z = 0.485). We conducted new multifrequency (0.3 - 5 GHz) Very Long Baseline Array (VLBA) and Jansky Very Large Array (JVLA) observations of CHIPS 1911+4455 across a wide range of scales (0.01 to 20 kpc). Our analysis reveals that the AGN in the BCG has recently awakened, showing a compact core with symmetric, ~30 pc long jets in VLBA data. The onset of the AGN may be linked to the enhanced cooling of the hot gas found in a previous study. At larger scales (10 kpc), faint radio whiskers extending to the south show a striking alignment with star-forming knots and are thus interpreted as synchrotron-emitting regions associated with the starburst BCG. The implied radio star formation rate of 100 - 155 M$_{\odot}$/yr agrees with the optical/infrared one (140 - 190 M$_{\odot}$/yr). Our JVLA and VLBA radio study, informed by previous X-ray/optical/millimeter works, indicates that CHIPS 1911+4455 represents a transitional phase in cluster evolution, where the AGN in the central galaxy has just begun to respond to copious hot gas cooling.

astro-ph.GA↗

arXiv2025

SZ-X-ray Surface Brightness Fluctuations in the SPT-XMM clusters

The hot plasma in galaxy clusters, the intracluster medium (ICM), is expected to be shaped by subsonic turbulent motions, which are key for heating, cooling, and transport mechanisms. The turbulent motions contribute to the non-thermal pressure which, if not accounted for, consequently imparts a hydrostatic mass bias. Accessing information about turbulent motions is thus of major astrophysical and cosmological interest. Characteristics of turbulent motions can be indirectly accessed through surface brightness fluctuations. This study expands on our pilot investigations of surface brightness fluctuations in the SZ and X-ray by examining, for the first time, a large sample of 60 clusters using \textit{both} SPT-SZ and XMM-Newton data and span the redshift range $0.2 < z < 1.5$, thus constraining the respective pressure and density fluctuations within 0.6~$R_{500}$. We deem density fluctuations to be of sufficient quality for 32 clusters, finding mild correlations between the peak of the amplitude spectra of density fluctuations and various dynamical parameters. We infer turbulent velocities from density fluctuations with an average Mach number $\mathcal{M}_{\text{3D}} = 0.52 \pm 0.14$, in agreement with numerical simulations. For clusters with inferred turbulent Mach numbers from both pressure, $\mathcal{M}_{\text{P}}$ and density fluctuations, $\mathcal{M}_ρ$, we find broad agreement between $\mathcal{M}_{\text{P}}$ and $\mathcal{M}_ρ$. Our results suggest either a bimodal or skewed unimodal Mach number distribution, with the majority of clusters being turbulence-dominated (subsonic) while the remainder are shock-dominated (supersonic).

astro-ph.CO↗

arXiv2025

Using the XMM-Newton small window mode to investigate systematic uncertainties in the particle background of X-ray charge-coupled device detectors

The level and uncertainty of the particle induced background in CCD detectors plays a crucial role for future X-ray instruments, such as the Wide Field Imager (WFI) onboard Athena. To mitigate the background systematic uncertainties, which will limit the Athena science goals, we aim to understand the relationship between the energetic charged particles interacting in the detector and satellite, and the instrumental science background to an unprecedented level. These particles produce easily identified "cosmic-ray tracks" along with less easily identified signals produced by secondary particles, e.g., X-rays generated by particle interactions with the instrument and indistinguishable from genuine sky X-rays. We utilize the Small Window Mode of the PN camera onboard XMM-Newton to understand the time, spatial and energy dependence of the various background components, particularly the particle induced background. While the distribution of particle events follows expected detector readout patterns, we find a particle track length distribution inconsistent with the simple, isotropic model. We also find that the detector mode-specific readout results in a shifted Cu fluorescent line. We illustrate that on long timescales the variability of the particle background correlates well with the solar cycle. This 20-year lightcurve, can be reproduced by a particle detector onboard Chandra, the HRC anti-coincidence shield. We conclude that the self-anti-coincidence method of removing X-ray-like events near detected particle tracks in the same frame can be optimized with the inclusion of additional information, such as the energy of the X-ray. The results presented here are relevant for any future pixelated X-ray imaging detector, and could allow the WFI to probe to truly faint X-ray surface brightness.

astro-ph.IM↗

arXiv2025

Revisiting the Group-Dominant Elliptical NGC 5044 in the Radio Band: Continuum Emission and Detection of HI Absorption

We present new MeerKAT L-band (continuum and HI) and upgraded Giant Metrewave Radio Telescope (300-850 MHz) observations of the archetypal cool-core group-dominant early-type galaxy NGC 5044. Our new continuum images reveal diffuse, steep spectrum ($α_{0.99\,\rm GHz}^{1.56\,\rm GHz}=-1.53\pm0.6$) radio emission extending about 25 kpc around the unresolved radio core. The observed radio emission overlaps with the known X-ray cavities, but is not confined to them. We also find the first direct evidence of neutral atomic gas in NGC 5044, in the form of a 3.8$σ$ significant two-component HI absorption line seen against the emission of the active nucleus. The peak velocities are well correlated with the previously reported CO(2-1) absorption, but the HI lines are moderately broader, spanning velocities from $265\,\rm \, km\,s^{-1}$ to $305\,\rm \, km\,s^{-1}$. We do not detect HI emission, but place an upper limit of $M_{HI}< 5.4 \times 10^{7} \, M_{\odot}$ in the central 15 arcsec (2.2 kpc) of the galaxy. This is significantly less than the estimated molecular gas content, and implies a molecular-to-atomic mass ratio of $\geq $1.7:1, consistent with these gas phases forming through cooling from the hot intra-group medium. We also constrain the spin temperature to $T_{\rm spin}\leq 950\,\rm K$, indicating that the detected HI is in the cold neutral phase.

astro-ph.GA↗

arXiv2024

Probing the high frequency variability of NGC 5044: the key to AGN feedback

The active galactic nucleus (AGN) feeding and feedback process in the centers of galaxy clusters and groups is still not well understood. NGC 5044 is the ideal system in which to study AGN feedback. It hosts the largest known reservoir of cold gas in any cool-core galaxy group, and features several past epochs of AGN feedback imprinted as cavities in the X-ray bright intragroup medium (IGrM), as well as parsec scale jets. We present Submillimeter Array (SMA), Karl G. Jansky Very Large Array (VLA), James Clerk Maxwell Telescope (JCMT), and Atacama Large Millimeter/submillimeter Array (ALMA) high frequency observations of NGC 5044 to assess the time variability of the mmwaveband emission from the accretion disk, and quantify the Spectral Energy Distribution (SED) from the radio to sub-millimeter band. The SED is well described by advection dominated accretion flow (ADAF) model and self-absorbed jet emission from an aging plasma with tau = 1kyr. We find a characteristic variability timescale of 150 days, which constrains the ADAF emission region to about 0.1pc, and the magnetic field to 4.7mG in the jets and and 870G in the accretion disk. A longer monitoring/sampling will allow to understand if the underlying process is truly periodic in nature.

astro-ph.GA↗

arXiv2024

Towards efficient machine-learning-based reduction of the cosmic-ray induced background in X-ray imaging detectors: increasing context awareness

Traditional cosmic ray filtering algorithms used in X-ray imaging detectors aboard space telescopes perform event reconstruction based on the properties of activated pixels above a certain energy threshold, within 3x3 or 5x5 pixel sliding windows. This approach can reject up to 98% of the cosmic ray background. However, the remaining unrejected background constitutes a significant impediment to studies of low surface brightness objects, which are especially prevalent in the high-redshift universe. The main limitation of the traditional filtering algorithms is their ignorance of the long-range contextual information present in image frames. This becomes particularly problematic when analyzing signals created by secondary particles produced during interactions of cosmic rays with body of the detector. Such signals may look identical to the energy deposition left by X-ray photons, when one considers only the properties within the small sliding window. Additional information is present, however, in the spatial and energy correlations between signals in different parts of the frame, which can be accessed by modern machine learning (ML) techniques. In this work, we continue the development of an ML-based pipeline for cosmic ray background mitigation. Our latest method consist of two stages: first, a frame classification neural network is used to create class activation maps (CAM), localizing all events within the frame; second, after event reconstruction, a random forest classifier, using features obtained from CAMs, is used to separate X-ray and cosmic ray features. The method delivers >40% relative improvement over traditional filtering in background rejection in standard 0.3-10keV energy range, at the expense of only a small (<2%) level of lost X-ray signal. Our method also provides a convenient way to tune the cosmic ray rejection threshold to adapt to a user's specific scientific needs.

astro-ph.IM↗

arXiv2024

Closing Pandora's Box -- The deepest X-ray observations of Abell 2744 and a multi-wavelength merger picture

Abell 2744, also known as Pandora's Cluster, is a complex merging galaxy cluster. While a major merger is clear along the north-south axis, the dynamical state of the northwest subcluster has been highly uncertain. We present ultra-deep ($\approx$2.1 Ms) X-ray observations of Abell 2744 obtained with the Chandra X-ray Observatory and reinterpret the multi-wavelength picture with a suite of idealised simulations of galaxy cluster mergers. The new data reveal in unprecedented detail the disruption of cool cores in the three X-ray luminous subclusters and confirm the presence of a shock to the NW. A position-velocity clustering of the cluster member galaxies shows a clearly separated S2 component, with a $Δz$ implying a separation of 53 Mpc or a line-of-sight velocity of $4500\ \rm{km \ s^{-1}}$, or likely some combination of the two. While binary simulations allow NW to have undergone a gravitational slingshot after the first pericenter passage, triple merger simulations rule out this scenario, because the two mergers would have had to occur $\sim$0.5 Gyr apart, and the joint impact of the shocks from the two mergers would completely disrupt the SE and NW cool cores; they only reform after 1-2 Gyr, by which point the core separations greatly exceed observations. The scenario that best describes Abell 2744 is a head-on N-S merger $0.5-0.6$ Gyrs ago followed by a first infall of the NW subcluster. Furthermore, we note that a model with three cluster-size halos, with masses consistent with gravitational lensing constraints, nevertheless produces a lensing convergence and surface brightness lower than observed in most of the field of view, whereas the temperatures are consistent with observations. This suggests the presence of a large-scale overdensity, which contributes to the diffuse emission and total surface density without heating the densest gas.

astro-ph.CO↗

arXiv2024

Active Galaxy Science with the Line Emission Mapper: The Case for High-Resolution Soft X-ray Spectroscopy

This white paper discusses the breadth of science related to active galactic nuclei (AGN) and associated phenomena to be enabled by a mission with microcalorimeter energy resolution in the soft X-ray band, a large collecting area, and wide-field imaging. Such a mission, the Line Emission Mapper (LEM), has been proposed to NASA's 2023 Astrophysics Probe Explorer call. While the science pillars of the PI-led part of the mission focus on galaxy evolution, the PI-led LEM All-Sky Survey (LASS) and General Observer/Investigator opportunities will enable vital discoveries for AGN science in the critical soft X-ray band.

astro-ph.HE↗

arXiv2024

A hot core in the group-dominant elliptical galaxy NGC 777

NGC 777 provides an example of a phenomenon observed in some group-central ellipticals, in which the temperature profile shows a central peak, despite the short central cooling time of the intra-group medium. We use deep Chandra X-ray observations of the galaxy, supported by uGMRT 400 MHz radio imaging, to investigate the origin of this hot core. We confirm the centrally-peaked temperature profile and find that entropy and cooling time both monotonically decline to low values (2.62 [+0.19, -0.18] keV cm$^2$ and 71.3 [+12.8, -13.1] Myr) in the central ~700 pc. Faint diffuse radio emission surrounds the nuclear point source, with no clear jets or lobes but extending to ~10 kpc on a northwest-southeast axis. This alignment and extent agree well with a previously identified filamentary H$α$+[NII] nebula. While cavities are not firmly detected, we see X-ray surface brightness decrements on the same axis at 10-20 kpc radius which are consistent with the intra-group medium having been pushed aside by expanding radio lobes. Any such outburst must have occurred long enough ago for lobe emission to have faded below detectability. Cavities on this scale would be capable of balancing radiative cooling for at least ~240 Myr. We consider possible causes of the centrally peaked temperature profile, including gravitational heating of gas as the halo relaxes after a period of AGN jet activity, and heating by particles leaking from the remnant relativistic plasma of the old radio jets.

astro-ph.GA↗

arXiv2024

Advancing Precision Particle Background Estimation for Future X-ray Missions: Correlated Variability between AMS and Chandra/XMM-Newton

Galactic cosmic ray (GCR) particles have a significant impact on the particle-induced background of X-ray observatories, and their flux exhibits substantial temporal variability, potentially influencing background levels. In this study, we present one-day binned high-energy reject rates derived from the Chandra-ACIS and XMM-Newton EPIC-pn instruments, serving as proxies for GCR particle flux. We systematically analyze the ACIS and EPIC-pn reject rates and compare them with the AMS proton flux. Our analysis initially reveals robust correlations between the AMS proton flux and the ACIS/EPIC-pn reject rates when binned over 27-day intervals. However, a closer examination reveals substantial fluctuations within each 27-day bin, indicating shorter-term variability. Upon daily binning, we observe finer. temporal structures in the datasets, demonstrating the presence of recurrent variations with periods of $\sim$ 25 days and 23 days in ACIS and EPIC-pn reject rates, respectively, spanning the years 2014 to 2018. Notably, during the 2016--2017 period, we additionally detect periodicities of $\sim$13.5 days and 9 days in the ACIS and EPIC-pn reject rates, respectively. Intriguingly, we observe a time lag of $\sim$ 6 days between the AMS proton flux and the ACIS/EPIC-pn reject rates during the second half of 2016. This time lag is not visible before 2016 and aftern2017. The underlying physical mechanisms responsible for this time lag remain a subject of ongoing investigation.

astro-ph.HE↗

arXiv2024

Mapping the imprints of stellar and AGN feedback in the circumgalactic medium with X-ray microcalorimeters

The Astro2020 Decadal Survey has identified the mapping of the circumgalactic medium (CGM, gaseous plasma around galaxies) as a key objective. We explore the prospects for characterizing the CGM in and around nearby galaxy halos with a future, large grasp X-ray microcalorimeter. We create realistic mock observations from hydrodynamical simulations (EAGLE, IllustrisTNG, and Simba) that demonstrate a wide range of potential measurements, which will address the open questions in galaxy formation and evolution. By including all background and foreground components in our mock observations, we show why it is impossible to perform these measurements with current instruments, such as X-ray CCDs, and only microcalorimeters will allow us to distinguish the faint CGM emission from the bright Milky Way (MW) foreground emission lines. We find that individual halos of MW mass can, on average and depending on star formation rate, be traced out to large radii, around R500, and for larger galaxies even out to R200, using prominent emission lines, such as OVII, or OVIII. Furthermore, we show that emission line ratios for individual halos can reveal the radial temperature structure. Substructure measurements show that it will be possible to relate azimuthal variations to the feedback mode of the galaxy. We demonstrate the ability to construct temperature, velocity, and abundance ratio maps from spectral fitting for individual galaxy halos, which reveal rotation features, AGN outbursts, and enrichment.

astro-ph.GA↗