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Showing 1-20 of about 26 results.
The mergers in Abell 2256: displaced gas and its connection to the radio-emitting plasmaBreuer, J. P.Werner, N.Mernier, F.Mroczkowski, T.Simionescu, A.Clarke, T. E.ZuHone, John A.Di Mascolo, L.DOI: info:10.1093/mnras/staa1492v. 4955014–5026
Breuer, J. P., Werner, N., Mernier, F., Mroczkowski, T., Simionescu, A., Clarke, T. E., ZuHone, John A., and Di Mascolo, L. 2020. "The mergers in Abell 2256: displaced gas and its connection to the radio-emitting plasma." Monthly Notices of the Royal Astronomical Society 495:5014– 5026.
ID: 158155
Type: article
Authors: Breuer, J. P.; Werner, N.; Mernier, F.; Mroczkowski, T.; Simionescu, A.; Clarke, T. E.; ZuHone, John A.; Di Mascolo, L.
Abstract: We present the results of deep Chandra and XMM-Newton X-ray imaging and spatially resolved spectroscopy of Abell 2256, a nearby (z = 0.058) galaxy cluster experiencing multiple mergers and displaying a rich radio morphology dominated by a large relic. The X-ray data reveal three subclusters: (I) the 'main cluster'; (II) the remnant of an older merger in the east of the cluster with an ∼600 kpc-long tail; (III) a bright, bullet-like, low-entropy infalling system, with a large line-of-sight velocity component. The low-entropy system displays a 250 kpc-long cold front with a break and an intriguing surface brightness decrement. Interestingly, the infalling gas is not co-spatial with bright galaxies and the radio-loud brightest cluster galaxy of the infalling group appears dissociated from the low-entropy plasma by ∼50 kpc in projection, to the south of the eastern edge of the cold front. Assuming that the dark matter follows the galaxy distribution, we predict that it is also significantly offset from the low-entropy gas. Part of the low-frequency radio emission near the cold front might be revived by magnetic field amplification due to differential gas motions. Using analytical models and numerical simulations, we investigate the possibility that the supersonic infall of the subcluster generates a large-scale shock along our line of sight, which can be detected in the X-ray temperature map but is not associated with any clear features in the surface brightness distribution.
Phase-modulated X-Ray Emission from Cepheids due to Pulsation-driven ShocksMoschou, Sofia-ParaskeviVlahakis, NektariosDrake, Jeremy J.Evans, Nancy RemageNeilson, Hilding R.Guzik, Joyce AnnZuhone, JohnDOI: info:10.3847/1538-4357/aba8fav. 900157
Moschou, Sofia-Paraskevi, Vlahakis, Nektarios, Drake, Jeremy J., Evans, Nancy Remage, Neilson, Hilding R., Guzik, Joyce Ann, and Zuhone, John. 2020. "Phase-modulated X-Ray Emission from Cepheids due to Pulsation-driven Shocks." The Astrophysical Journal 900:157.
ID: 157760
Type: article
Authors: Moschou, Sofia-Paraskevi; Vlahakis, Nektarios; Drake, Jeremy J.; Evans, Nancy Remage; Neilson, Hilding R.; Guzik, Joyce Ann; Zuhone, John
Abstract: Cepheids are pulsating variable stars with a periodic chromospheric response at UV wavelengths close to their minimum radius phase. Recently, an X-ray variable signature was captured in observations during the maximum radius phase. This X-ray emission came as a surprise and is not understood. In this work, we use the modern astrophysical code PLUTO to investigate the effects of pulsations on Cepheid X-ray emission. We run a number of hydrodynamic numerical simulations with a variety of initial and boundary conditions in order to explore the capability of shocks to produce the observed phase-dependent X-ray behavior. Finally, we use the Simulated Observations of X-ray Sources (SOXS) package to create synthetic spectra for each simulation case and link our simulations to observables. We show that, for certain conditions, we can reproduce observed X-ray fluxes at phases 0.4-0.8 when the Cepheid is at maximum radius. Our results span a wide range of mass-loss rates, 2 × 10-13 M yr-1 to 3 × 10-8 M yr-1, and peak X-ray luminosities, 5 × 10-17 erg cm-2 s-1 to 1.4 × 10-12 erg cm-2 s-1. We conclude that Cepheids exhibit two-component emission with (a) shock waves being responsible for the phase-dependent variable emission (phases 0.2-0.6) and (b) a separate quiescent mechanism being the dominant emission mechanism for the remaining phases.
EAGLE and Illustris-TNG Predictions for Resolved eROSITA X-Ray Observations of the Circumgalactic Medium around Normal GalaxiesOppenheimer, Benjamin D.Bogdán, ÁkosCrain, Robert A.ZuHone, John A.Forman, William R.Schaye, JoopWijers, Nastasha A.Davies, Jonathan J.Jones, ChristineKraft, Ralph P.Ghirardini, VittorioDOI: info:10.3847/2041-8213/ab846fv. 893L24
Oppenheimer, Benjamin D., Bogdán, Ákos, Crain, Robert A., ZuHone, John A., Forman, William R., Schaye, Joop, Wijers, Nastasha A., Davies, Jonathan J., Jones, Christine, Kraft, Ralph P., and Ghirardini, Vittorio. 2020. "EAGLE and Illustris-TNG Predictions for Resolved eROSITA X-Ray Observations of the Circumgalactic Medium around Normal Galaxies." The Astrophysical Journal 893:L24.
ID: 157301
Type: article
Authors: Oppenheimer, Benjamin D.; Bogdán, Ákos; Crain, Robert A.; ZuHone, John A.; Forman, William R.; Schaye, Joop; Wijers, Nastasha A.; Davies, Jonathan J.; Jones, Christine; Kraft, Ralph P.; Ghirardini, Vittorio
Abstract: We simulate stacked observations of nearby hot X-ray coronae associated with galaxies in the EAGLE and Illustris-TNG hydrodynamic simulations. A forward modeling pipeline is developed to predict 4 yr eROSITA observations and stacked image analysis, including the effects of instrumental and astrophysical backgrounds. We propose an experiment to stack z ≍ 0.01 galaxies separated by specific star formation rate (sSFR) to examine how the hot (T ≥ 106 K) circumgalactic medium (CGM) differs for high- and low-sSFR galaxies. The simulations indicate that the hot CGM of low-mass ( ${M}_{* }\approx {10}^{10.5}\ {M}_{\odot }$ ), high-sSFR (defined as the top one-third ranked by sSFR) central galaxies will be detectable to a galactocentric radius r ≍ 30-50 kpc. Both simulations predict lower luminosities at fixed stellar mass for the low-sSFR galaxies (the lower third of sSFR) with Illustris-TNG predicting 3× brighter coronae around high-sSFR galaxies than EAGLE. Both simulations predict detectable emission out to r ≍ 150-200 kpc for stacks centered on high-mass ( ${M}_{* }\approx {10}^{11.0}\ {M}_{\odot }$ ) galaxies, with EAGLE predicting brighter X-ray halos. The extended soft X-ray luminosity correlates strongly and positively with the mass of circumgalactic gas within the virial radius (fCGM). Prior analyses of both simulations have established that fCGM is reduced by expulsive feedback driven mainly by black hole growth, which quenches galaxy growth by inhibiting replenishment of the interstellar medium. Both simulations predict that eROSITA stacks should not only conclusively detect and resolve the hot CGM around L* galaxies for the first time, but provide a powerful probe of how the baryon cycle operates, for which there remains an absence of consensus between state- of-the-art simulations.
Measuring bulk flows of the intracluster medium in the Perseus and Coma galaxy clusters using XMM-NewtonSanders, J. S.Dennerl, K.Russell, H. R.Eckert, D.Pinto, C.Fabian, A. C.Walker, S. A.Tamura, T.Zuhone, JohnHofmann, F.DOI: info:10.1051/0004-6361/201936468v. 633A42
Sanders, J. S., Dennerl, K., Russell, H. R., Eckert, D., Pinto, C., Fabian, A. C., Walker, S. A., Tamura, T., Zuhone, John, and Hofmann, F. 2020. "Measuring bulk flows of the intracluster medium in the Perseus and Coma galaxy clusters using XMM-Newton." Astronomy and Astrophysics 633:A42.
ID: 155670
Type: article
Authors: Sanders, J. S.; Dennerl, K.; Russell, H. R.; Eckert, D.; Pinto, C.; Fabian, A. C.; Walker, S. A.; Tamura, T.; Zuhone, John; Hofmann, F.
Abstract: We demonstrate a novel technique for calibrating the energy scale of theE PIC-pn detector on XMM-Newton, which allows us to measure bulk flows inthe intracluster medium (ICM) of the Perseus and Coma galaxy clusters. The procedure uses the fluorescent instrumental background lines present in all observations, in particular, Cu-Kα. By studying their spatial and temporal variations, in addition to incorporating calibration observations, we refined the absolute energy scale of the detector to better than 150 km s-1 at the Fe-K line, a large improvement over the nominal calibration accuracy of 550 km s-1. With our calibration, we mapped the bulk motions over much of the central 1200 and 800 kpc of Perseus and Coma, respectively, in spatial regions down to 65 and 140 kpc size. We cross-checked our procedure by comparing our measurements with those found in Perseus by Hitomi for an overlapping 65 kpc square region, finding consistent results. For Perseus, there is a relative line-of-sight velocity increase of 480 ± 210 km s-1 (1σ) at a radius of 250 kpc east of the nucleus. This region is associated with a cold front, providing direct evidence of the ICM sloshing in the cluster potential well. Assuming the intrinsic distribution of bulk motions is Gaussian, its width is 214 ± 85 km s-1, excluding systematic uncertainties. Removing the sloshing region, this is reduced to 20-150 km s-1, which is similar in magnitude to the Hitomi line width measurements in undisturbed regions. In Coma, the line-of-sight velocity of the ICM varies between the velocities of the two central galaxies. Maps of the gas velocity and metallicity provide clues about the merger history of the Coma, with material to the north and east of the cluster core having a velocity similar to NGC 4874, while that to the south and west has velocities close to NGC 4889. Our results highlight the difference between a merging system, such as Coma, where we observe a ∼1000 km s-1 range in velocity, and a relatively relaxed system, such as Perseus, with much weaker bulk motions. Tables A.1 and A.2 are only available at the CDS via anonymous ftp to ( or via
A deep learning view of the census of galaxy clusters in IllustrisTNGSu, Y.Zhang, Y.Liang, G.ZuHone, John A.Barnes, D. J.Jacobs, N. B.Ntampaka, MichelleForman, William R.Nulsen, Paul E. J.Kraft, Ralph P.Jones, C.DOI: info:10.1093/mnras/staa2690v. 4985620–5628
Su, Y., Zhang, Y., Liang, G., ZuHone, John A., Barnes, D. J., Jacobs, N. B., Ntampaka, Michelle, Forman, William R., Nulsen, Paul E. J., Kraft, Ralph P., and Jones, C. 2020. "A deep learning view of the census of galaxy clusters in IllustrisTNG." Monthly Notices of the Royal Astronomical Society 498:5620– 5628.
ID: 158586
Type: article
Authors: Su, Y.; Zhang, Y.; Liang, G.; ZuHone, John A.; Barnes, D. J.; Jacobs, N. B.; Ntampaka, Michelle; Forman, William R.; Nulsen, Paul E. J.; Kraft, Ralph P.; Jones, C.
Abstract: The origin of the diverse population of galaxy clusters remains an unexplained aspect of large-scale structure formation and cluster evolution. We present a novel method of using X-ray images to identify cool core (CC), weak cool core (WCC), and non-cool core (NCC) clusters of galaxies that are defined by their central cooling times. We employ a convolutional neural network, ResNet-18, which is commonly used for image analysis, to classify clusters. We produce mock Chandra X-ray observations for a sample of 318 massive clusters drawn from the IllustrisTNG simulations. The network is trained and tested with low-resolution mock Chandra images covering a central 1 Mpc square for the clusters in our sample. Without any spectral information, the deep learning algorithm is able to identify CC, WCC, and NCC clusters, achieving balanced accuracies (BAcc) of 92 per cent, 81 per cent, and 83 per cent, respectively. The performance is superior to classification by conventional methods using central gas densities, with an average ${\rm BAcc}=81{{\ \rm per\ cent}}$ , or surface brightness concentrations, giving ${\rm BAcc}=73{{\ \rm per\ cent}}$ . We use class activation mapping to localize discriminative regions for the classification decision. From this analysis, we observe that the network has utilized regions from cluster centres out to r ? 300 kpc and r ? 500 kpc to identify CC and NCC clusters, respectively. It may have recognized features in the intracluster medium that are associated with AGN feedback and disruptive major mergers.
A Parameter Space Exploration of Galaxy Cluster Mergers. II. Effects of Magnetic FieldsBrzycki, BryanZuhone, JohnDOI: info:10.3847/1538-4357/ab3983v. 883118
Brzycki, Bryan and Zuhone, John. 2019. "A Parameter Space Exploration of Galaxy Cluster Mergers. II. Effects of Magnetic Fields." The Astrophysical Journal 883:118.
ID: 154632
Type: article
Authors: Brzycki, Bryan; Zuhone, John
Abstract: The hot intracluster plasma in clusters of galaxies is weakly magnetized. Mergers between clusters produce gas compression and motions that can increase the magnetic field strength. In this work, we perform high-resolution nonradiative magnetohydrodynamics simulations of binary galaxy cluster mergers with magnetic fields, to examine the effects of these motions on the magnetic field configuration and strength, as well as the effect of the field on the gas itself. Our simulations sample a parameter space of initial mass ratios and impact parameters. During the first core passage of mergers, the magnetic energy increases via gas compression. After this, shear flows produce temporary, megaparsec- scale, strong-field "filament" structures. Lastly, magnetic fields grow stronger by turbulence. Field amplification is most effective for low- mass ratio mergers, but mergers with a large impact parameter can increase the magnetic energy more via shearing motions. The amplification of the magnetic field is most effective in between the first two core passages of each cluster merger. After the second core passage, the magnetic energy in this region gradually decreases. In general, the transfer of energy from gas motions to the magnetic field is not significant enough to have a substantial effect on gas mixing and the subsequent increase in entropy, which occurs in cluster cores as a result. In the absence of radiative cooling, this results in an overall decrease of the magnetic field strength in cluster cores. In these regions, the final magnetic field is isotropic, while it can be significantly tangential at larger radii.
Using X-Ray Morphological Parameters to Strengthen Galaxy Cluster Mass Estimates via Machine LearningGreen, Sheridan B.Ntampaka, MichelleNagai, DaisukeLovisari, LorenzoDolag, KlausEckert, DominiqueZuHone, John A.DOI: info:10.3847/1538-4357/ab426fv. 88433
Green, Sheridan B., Ntampaka, Michelle, Nagai, Daisuke, Lovisari, Lorenzo, Dolag, Klaus, Eckert, Dominique, and ZuHone, John A. 2019. "Using X-Ray Morphological Parameters to Strengthen Galaxy Cluster Mass Estimates via Machine Learning." The Astrophysical Journal 884:33.
ID: 154618
Type: article
Authors: Green, Sheridan B.; Ntampaka, Michelle; Nagai, Daisuke; Lovisari, Lorenzo; Dolag, Klaus; Eckert, Dominique; ZuHone, John A.
Abstract: We present a machine-learning approach for estimating galaxy cluster masses, trained using both Chandra and eROSITA mock X-ray observations of 2041 clusters from the Magneticum simulations. We train a random forest (RF) regressor, an ensemble learning method based on decision tree regression, to predict cluster masses using an input feature set. The feature set uses core-excised X-ray luminosity and a variety of morphological parameters, including surface brightness concentration, smoothness, asymmetry, power ratios, and ellipticity. The regressor is cross-validated and calibrated on a training sample of 1615 clusters (80% of sample), and then results are reported as applied to a test sample of 426 clusters (20% of sample). This procedure is performed for two different mock observation series in an effort to bracket the potential enhancement in mass predictions that can be made possible by including dynamical state information. The first series is computed from idealized Chandra-like mock cluster observations, with high spatial resolution, long exposure time (1 Ms), and the absence of background. The second series is computed from realistic-condition eROSITA mocks with lower spatial resolution, short exposures (2 ks), instrument effects, and background photons modeled. We report a 20% reduction in the mass estimation scatter when either series is used in our RF model compared to a standard regression model that only employs core-excised luminosity. The morphological parameters that hold the highest feature importance are smoothness, asymmetry, and surface brightness concentration. Hence these parameters, which encode the dynamical state of the cluster, can be used to make more accurate predictions of cluster masses in upcoming surveys, offering a crucial step forward for cosmological analyses.
Effects of Anisotropic Viscosity on the Evolution of Active Galactic Nuclei Bubbles in Galaxy ClustersKingsland, MatthewYang, H. -Y KarenReynolds, Christopher S.ZuHone, John A.DOI: info:10.3847/2041-8213/ab40bev. 883L23
Kingsland, Matthew, Yang, H. -Y Karen, Reynolds, Christopher S., and ZuHone, John A. 2019. "Effects of Anisotropic Viscosity on the Evolution of Active Galactic Nuclei Bubbles in Galaxy Clusters." The Astrophysical Journal 883:L23.
ID: 154404
Type: article
Authors: Kingsland, Matthew; Yang, H. -Y Karen; Reynolds, Christopher S.; ZuHone, John A.
Abstract: The interaction between jets from active galactic nuclei (AGNs) and the intracluster medium (ICM) provides key constraints on the feeding and feedback of supermassive black holes. Much understanding about AGN feedback is gained from purely hydrodynamic models; however, whether such an approximation is adequate for the magnetized, weakly collisional ICM needs to be critically examined. For example, AGN-blown bubbles in hydrodynamic simulations are easily disrupted by fluid instabilities, making it difficult to explain the coherence of observed bubbles such as the northwest ghost bubble in Perseus. In order to investigate whether magnetic tension and viscosity in realistic conditions could preserve the bubble integrity, we performed the first Braginskii- magnetohydrodynamic simulations of jet-inflated bubbles in a medium with tangled magnetic field. We find that magnetic tension alone is insufficient to prevent bubble deformation due to large velocity shear at early stage of the evolution. Although unsuppressed anisotropic viscosity in tangled magnetic field can have similar effects as isotropic viscosity, when the pressure anisotropy is bounded by microscopic plasma instabilities, the level of viscosity is substantially limited, thereby failing to prevent bubble deformation as in the inviscid case. Our results suggest that Braginskii viscosity is unlikely to be the primary mechanism for suppressing the fluid instabilities for AGN bubbles, and it remains a challenging task to reproduce smooth and coherent bubbles as observed. Because the dynamical influence and heating of the ICM critically depend on the bubble morphology, our study highlights the fundamental role of "microphysics" on the macroscopic properties of AGN feedback processes.
Astrophysics with the Spatially and Spectrally Resolved Sunyaev-Zeldovich Effects. A Millimetre/Submillimetre Probe of the Warm and Hot UniverseMroczkowski, TonyNagai, DaisukeBasu, KaustuvChluba, JensSayers, JackAdam, RémiChurazov, EugeneCrites, AbigailDi Mascolo, LucaEckert, DominiqueMacias-Perez, JuanMayet, FrédéricPerotto, LaurencePointecouteau, EtienneRomero, CharlesRuppin, FlorianScannapieco, EvanZuhone, JohnDOI: info:10.1007/s11214-019-0581-2v. 21517
Mroczkowski, Tony, Nagai, Daisuke, Basu, Kaustuv, Chluba, Jens, Sayers, Jack, Adam, Rémi, Churazov, Eugene, Crites, Abigail, Di Mascolo, Luca, Eckert, Dominique, Macias-Perez, Juan, Mayet, Frédéric, Perotto, Laurence, Pointecouteau, Etienne, Romero, Charles, Ruppin, Florian, Scannapieco, Evan, and Zuhone, John. 2019. "Astrophysics with the Spatially and Spectrally Resolved Sunyaev-Zeldovich Effects. A Millimetre/Submillimetre Probe of the Warm and Hot Universe." Space Science Reviews 215:17.
ID: 150517
Type: article
Authors: Mroczkowski, Tony; Nagai, Daisuke; Basu, Kaustuv; Chluba, Jens; Sayers, Jack; Adam, Rémi; Churazov, Eugene; Crites, Abigail; Di Mascolo, Luca; Eckert, Dominique; Macias-Perez, Juan; Mayet, Frédéric; Perotto, Laurence; Pointecouteau, Etienne; Romero, Charles; Ruppin, Florian; Scannapieco, Evan; Zuhone, John
Abstract: In recent years, observations of the Sunyaev-Zeldovich (SZ) effect have had significant cosmological implications and have begun to serve as a powerful and independent probe of the warm and hot gas that pervades the Universe. As a few pioneering studies have already shown, SZ observations both complement X-ray observations—the traditional tool for studying the intra-cluster medium—and bring unique capabilities for probing astrophysical processes at high redshifts and out to the low-density regions in the outskirts of galaxy clusters. Advances in SZ observations have largely been driven by developments in centimetre-, millimetre-, and submillimetre-wave instrumentation on ground-based facilities, with notable exceptions including results from the Planck satellite. Here we review the utility of the thermal, kinematic, relativistic, non-thermal, and polarised SZ effects for studies of galaxy clusters and other large scale structures, incorporating the many advances over the past two decades that have impacted SZ theory, simulations, and observations. We also discuss observational results, techniques, and challenges, and aim to give an overview and perspective on emerging opportunities, with the goal of highlighting some of the exciting new directions in this field.
A Deep Learning Approach to Galaxy Cluster X-Ray MassesNtampaka, MichelleZuHone, J.Eisenstein, D.Nagai, D.Vikhlinin, A.Hernquist, L.Marinacci, F.Nelson, D.Pakmor, R.Pillepich, A.Torrey, P.Vogelsberger, M.DOI: info:10.3847/1538-4357/ab14ebv. 87682
Ntampaka, Michelle, ZuHone, J., Eisenstein, D., Nagai, D., Vikhlinin, A., Hernquist, L., Marinacci, F., Nelson, D., Pakmor, R., Pillepich, A., Torrey, P., and Vogelsberger, M. 2019. "A Deep Learning Approach to Galaxy Cluster X-Ray Masses." The Astrophysical Journal 876:82.
ID: 151867
Type: article
Authors: Ntampaka, Michelle; ZuHone, J.; Eisenstein, D.; Nagai, D.; Vikhlinin, A.; Hernquist, L.; Marinacci, F.; Nelson, D.; Pakmor, R.; Pillepich, A.; Torrey, P.; Vogelsberger, M.
Abstract: We present a machine-learning (ML) approach for estimating galaxy cluster masses from Chandra mock images. We utilize a Convolutional Neural Network (CNN), a deep ML tool commonly used in image recognition tasks. The CNN is trained and tested on our sample of 7896 Chandra X-ray mock observations, which are based on 329 massive clusters from the {\text{}}{IllustrisTNG} simulation. Our CNN learns from a low resolution spatial distribution of photon counts and does not use spectral information. Despite our simplifying assumption to neglect spectral information, the resulting mass values estimated by the CNN exhibit small bias in comparison to the true masses of the simulated clusters (‑0.02 dex) and reproduce the cluster masses with low intrinsic scatter, 8% in our best fold and 12% averaging over all. In contrast, a more standard core-excised luminosity method achieves 15%–18% scatter. We interpret the results with an approach inspired by Google DeepDream and find that the CNN ignores the central regions of clusters, which are known to have high scatter with mass.
Imaging the Thermal and Kinematic Sunyaev-Zel'dovich Effect Signals in a Sample of 10 Massive Galaxy Clusters: Constraints on Internal Velocity Structures and Bulk VelocitiesSayers, JackMontaña, AlfredoMroczkowski, TonyWilson, Grant W.Zemcov, MichaelZitrin, AdiCibirka, NatháliaGolwala, SunilHughes, DavidNagai, DaisukeReese, Erik D.Sánchez, DavidZuhone, JohnDOI: info:10.3847/1538-4357/ab29efv. 88045
Sayers, Jack, Montaña, Alfredo, Mroczkowski, Tony, Wilson, Grant W., Zemcov, Michael, Zitrin, Adi, Cibirka, Nathália, Golwala, Sunil, Hughes, David, Nagai, Daisuke, Reese, Erik D., Sánchez, David, and Zuhone, John. 2019. "Imaging the Thermal and Kinematic Sunyaev-Zel'dovich Effect Signals in a Sample of 10 Massive Galaxy Clusters: Constraints on Internal Velocity Structures and Bulk Velocities." The Astrophysical Journal 880:45.
ID: 154161
Type: article
Authors: Sayers, Jack; Montaña, Alfredo; Mroczkowski, Tony; Wilson, Grant W.; Zemcov, Michael; Zitrin, Adi; Cibirka, Nathália; Golwala, Sunil; Hughes, David; Nagai, Daisuke; Reese, Erik D.; Sánchez, David; Zuhone, John
Abstract: We have imaged the Sunyaev-Zel'dovich (SZ) effect signals at 140 and 270 GHz toward 10 galaxy clusters with Bolocam and AzTEC/ASTE. We also used Planck data to constrain the signal at large angular scales, Herschel- SPIRE images to subtract the brightest galaxies that comprise the cosmic infrared background (CIB), Chandra imaging to map the electron temperature Te of the intra-cluster medium, and Hubble Space Telescope imaging to derive models of each galaxy cluster's mass density. The galaxy clusters gravitationally lens the background CIB, which produced an on-average reduction in brightness toward the galaxy clusters' centers after the brightest galaxies were subtracted. We corrected for this deficit, which was between 5% and 25% of the 270 GHz SZ effect signal within R 2500. Using the SZ effect measurements, along with the X-ray constraint on Te, we measured each galaxy cluster's average line of sight (LOS) velocity vz within R 2500, with a median per-cluster uncertainty of ±700 km s-1. We found an ensemble-mean &lt vz > of 430 ± 210 km s-1, and an intrinsic cluster-to-cluster scatter σint of 470 ± 340 km s-1. We also obtained maps of vz over each galaxy cluster's face with an angular resolution of 70". All four galaxy clusters previously identified as having a merger oriented along the LOS showed an excess variance in these maps at a significance of ≃2-4σ, indicating an internal vz rms of ≳1000 km s-1. None of the six galaxy clusters previously identified as relaxed or plane-of-sky mergers showed any such excess variance.
A New Class of X-Ray Tails of Early-type Galaxies and Subclusters in Galaxy Clusters: Slingshot Tails versus Ram Pressure Stripped TailsSheardown, AlexFish, Thomas M.Roediger, ElkeHunt, MatthewZuhone, JohnSu, YuanyuanKraft, Ralph P.Nulsen, PaulChurazov, EugeneForman, WilliamJones, ChristineLyskova, NatalyaEckert, DominiqueDe Grandi, SabrinaDOI: info:10.3847/1538-4357/ab0c06v. 874112
Sheardown, Alex, Fish, Thomas M., Roediger, Elke, Hunt, Matthew, Zuhone, John, Su, Yuanyuan, Kraft, Ralph P., Nulsen, Paul, Churazov, Eugene, Forman, William, Jones, Christine, Lyskova, Natalya, Eckert, Dominique, and De Grandi, Sabrina. 2019. "A New Class of X-Ray Tails of Early-type Galaxies and Subclusters in Galaxy Clusters: Slingshot Tails versus Ram Pressure Stripped Tails." The Astrophysical Journal 874:112.
ID: 155315
Type: article
Authors: Sheardown, Alex; Fish, Thomas M.; Roediger, Elke; Hunt, Matthew; Zuhone, John; Su, Yuanyuan; Kraft, Ralph P.; Nulsen, Paul; Churazov, Eugene; Forman, William; Jones, Christine; Lyskova, Natalya; Eckert, Dominique; De Grandi, Sabrina
Abstract: We show that there is a new class of gas tails-slingshot tails-that form as a subhalo (i.e., a subcluster or early-type cluster galaxy) moves away from the cluster center toward the apocenter of its orbit. These tails can point perpendicular or even opposite to the subhalo direction of motion, not tracing the recent orbital path. Thus, the observed tail direction can be misleading, and we caution against naive conclusions regarding the subhalo's direction of motion based on the tail direction. A head-tail morphology of a galaxy's or subcluster's gaseous atmosphere is usually attributed to ram pressure stripping, and the widely applied conclusion is that gas stripped tail traces the most recent orbit. However, during the slingshot tail stage, the subhalo is not being ram pressure stripped (RPS) and the tail is shaped by tidal forces more than just the ram pressure. Thus, applying a classic RPS scenario to a slingshot tail leads not only to an incorrect conclusion regarding the direction of motion but also to incorrect conclusions regarding the subhalo velocity, expected locations of shear flows, instabilities, and mixing. We describe the genesis and morphology of slingshot tails using data from binary cluster merger simulations and discuss their observable features and how to distinguish them from classic RPS tails. We identify three examples from the literature that are not RPS tails but slingshot tails and discuss other potential candidates.
Constraining Gas Motions in the Intra-Cluster MediumSimionescu, AuroraZuhone, JohnZhuravleva, IrinaChurazov, EugeneGaspari, MassimoNagai, DaisukeWerner, NorbertRoediger, ElkeCanning, RebeccaEckert, DominiqueGu, LiyiPaerels, FritsDOI: info:10.1007/s11214-019-0590-1v. 21524
Simionescu, Aurora, Zuhone, John, Zhuravleva, Irina, Churazov, Eugene, Gaspari, Massimo, Nagai, Daisuke, Werner, Norbert, Roediger, Elke, Canning, Rebecca, Eckert, Dominique, Gu, Liyi, and Paerels, Frits. 2019. "Constraining Gas Motions in the Intra-Cluster Medium." Space Science Reviews 215:24.
ID: 150526
Type: article
Authors: Simionescu, Aurora; Zuhone, John; Zhuravleva, Irina; Churazov, Eugene; Gaspari, Massimo; Nagai, Daisuke; Werner, Norbert; Roediger, Elke; Canning, Rebecca; Eckert, Dominique; Gu, Liyi; Paerels, Frits
Abstract: The detailed velocity structure of the diffuse X-ray emitting intra-cluster medium (ICM) remains one of the last missing key ingredients in understanding the microphysical properties of these hot baryons and constraining our models of the growth and evolution of structure on the largest scales in the Universe. Direct measurements of the gas velocities from the widths and shifts of X-ray emission lines were recently provided for the central region of the Perseus Cluster of galaxies by Hitomi, and upcoming high-resolution X-ray microcalorimeters onboard XRISM and Athena are expected to extend these studies to many more systems. In the mean time, several other direct and indirect methods have been proposed for estimating the velocity structure in the ICM, ranging from resonant scattering to X-ray surface brightness fluctuation analysis, the kinematic Sunyaev-Zeldovich effect, or using optical line emitting nebulae in the brightest cluster galaxies as tracers of the motions of the ambient plasma. Here, we review and compare the existing estimates of the velocities of the hot baryons, as well as the various overlapping physical processes that drive motions in the ICM, and discuss the implications of these measurements for constraining the viscosity and identifying the source of turbulence in clusters of galaxies.
Nonequilibrium Ionization in Mixed-morphology Supernova RemnantsZhang, Gao-YuanSlavin, Jonathan D.Foster, AdamSmith, Randall K.ZuHone, John A.Zhou, PingChen, YangDOI: info:10.3847/1538-4357/ab0f9av. 87581
Zhang, Gao-Yuan, Slavin, Jonathan D., Foster, Adam, Smith, Randall K., ZuHone, John A., Zhou, Ping, and Chen, Yang. 2019. "Nonequilibrium Ionization in Mixed-morphology Supernova Remnants." The Astrophysical Journal 875:81.
ID: 155248
Type: article
Authors: Zhang, Gao-Yuan; Slavin, Jonathan D.; Foster, Adam; Smith, Randall K.; ZuHone, John A.; Zhou, Ping; Chen, Yang
Abstract: The mixed-morphology class of supernova remnants (MMSNRs) comprises a substantial fraction of observed remnants, but there is no consensus on their origin as yet. A clue to their nature is the presence of regions that show X-ray evidence of recombining plasmas. Recent calculations of remnant evolution in a cloudy interstellar medium that included thermal conduction but not nonequilibrium ionization (NEI) showed promise in explaining observed surface brightness distributions but could not determine whether recombining plasmas were present. In this paper, we present numerical hydrodynamic models of MMSNRs in 2D and 3D, including explicit calculation of NEI effects. Both the spatial ionization distribution and temperature-density diagrams show that recombination occurs inside the simulated MMSNR and that both adiabatic expansion and thermal conduction cause recombination, albeit in different regions. Features created by the adiabatic expansion stand out in the spatial and temperature-density diagrams, but thermal conduction also plays a role. Thus, thermal conduction and adiabatic expansion both contribute significantly to the cooling of high-temperature gas. Realistic observational data are simulated with both spatial and spectral input from various regions. We also discuss the possibility of analyzing the sources of recombination and dominant hydrodynamic processes in observations using temperature-density diagrams and spatial maps.
Testing Emergent Gravity with Optical, X-Ray, and Weak Lensing Measurements in Massive, Relaxed Galaxy ClustersZuHone, John A.Sims, J.DOI: info:10.3847/1538-4357/ab2b34v. 880145
ZuHone, John A. and Sims, J. 2019. "Testing Emergent Gravity with Optical, X-Ray, and Weak Lensing Measurements in Massive, Relaxed Galaxy Clusters." The Astrophysical Journal 880:145.
ID: 154267
Type: article
Authors: ZuHone, John A.; Sims, J.
Abstract: We test the predictions of emergent gravity (EG) using matter densities of relaxed, massive clusters of galaxies observed from optical and X-ray wavebands. We improve upon previous work in this area by including the baryon mass contribution of the brightest cluster galaxy (BCG) in each system, in addition to total mass profiles from gravitational lensing and mass profiles of the X-ray emitting gas from Chandra. We use this data in the context of EG to predict the "apparent" dark matter (DM) distribution from the observed baryon distribution, and vice versa. We find that although the inclusion of the BCG in the analysis improves the agreement with observations in the inner regions of the clusters (r≲ 10{--}30 kpc), at larger radii (r̃ 100{--}200 kpc) the EG predictions for mass profiles and baryon mass fractions are not in agreement with observations by a factor of up to ̃2-6, though the agreement improves at radii near r 500. At least in its current form, EG does not appear to reproduce the observed characteristics of relaxed galaxy clusters as well as cold DM models.
Sloshing of Galaxy Cluster Core Plasma in the Presence of Self-interacting Dark MatterZuHone, John A.Zavala, J.Vogelsberger, M.DOI: info:10.3847/1538-4357/ab321dv. 882119
ZuHone, John A., Zavala, J., and Vogelsberger, M. 2019. "Sloshing of Galaxy Cluster Core Plasma in the Presence of Self-interacting Dark Matter." The Astrophysical Journal 882:119.
ID: 154443
Type: article
Authors: ZuHone, John A.; Zavala, J.; Vogelsberger, M.
Abstract: The "sloshing" of the cold gas in the cores of relaxed clusters of galaxies is a widespread phenomenon evidenced by the presence of spiral- shaped "cold fronts" in X-ray observations of these systems. In simulations, these flows of cold gas readily form via interactions of the cluster core with small subclusters, due to a separation of the cold gas from the dark matter (DM), due to their markedly different collisionalities. In this work, we use numerical simulations to investigate the effects of increasing the DM collisionality on sloshing cold fronts in a cool-core cluster. For clusters in isolation, the formation of a flat DM core via self-interactions results in modest adiabatic expansion and cooling of the core gas. In merger simulations, cold fronts form in the same manner as in previous simulations, but the flattened potential in the core region enables the gas to expand to larger radii in the initial stages. Upon infall, the subclusters DM mass decreases via collisions, reducing its influence on the core. Thus, the sloshing gas moves slower, inhibiting the growth of fluid instabilities relative to simulations where the DM cross section is zero. This also inhibits turbulent mixing and the increase in entropy that would otherwise result. For values of the cross section σ/m ≳ 1, subclusters do not survive as self-gravitating structures for more than two core passages. Additionally, separations between the peaks in the X-ray emissivity and thermal Sunyaev-Zeldovich effect signals during sloshing may place constraints on DM self-interactions.
The Megaparsec-scale Gas-sloshing Spiral in the Remnant Cool Core Cluster Abell 1763Douglass, E. M.Blanton, E. L.Randall, Scott W.Clarke, T. E.Edwards, L. O. V.Sabry, Z.ZuHone, John A.DOI: info:10.3847/1538-4357/aae9e7v. 868121
Douglass, E. M., Blanton, E. L., Randall, Scott W., Clarke, T. E., Edwards, L. O. V., Sabry, Z., and ZuHone, John A. 2018. "The Megaparsec-scale Gas-sloshing Spiral in the Remnant Cool Core Cluster Abell 1763." The Astrophysical Journal 868:121.
ID: 150185
Type: article
Authors: Douglass, E. M.; Blanton, E. L.; Randall, Scott W.; Clarke, T. E.; Edwards, L. O. V.; Sabry, Z.; ZuHone, John A.
Abstract: We present a multiwavelength study of the massive galaxy cluster Abell 1763 at redshift z = 0.231. Image analysis of a 19.6 ks Chandra archival observation reveals a cluster-wide spiral of enhanced surface brightness in the intracluster medium (ICM). While such spirals are understood to form in clusters with sloshing strong cool cores (SCCs), the gas comprising the spiral’s apex is of intermediate entropy (∼110 keV cm2) and cooling time (∼6.8 Gyr), indicating core disruption is occurring throughout the spiral formation process. Two subclusters dominated by the second- and third-ranked galaxies in the system lie along a line parallel to the elongation axis of the primary cluster’s ICM. Both subsystems appear to have fallen in along a previously discovered intercluster filament and are each considered candidates as the perturber responsible for initiating disruptive core sloshing. Dynamical analysis indicates infall is occurring with a relative radial velocity of ∼1800 km s‑1. The brightest cluster galaxy of Abell 1763 possesses a high line-of-sight peculiar velocity (v pec ∼ 650 km s‑1) and hosts a powerful (P 1.4 ∼ 1026 W Hz‑1) bent double-lobed radio source, likely shaped by the relative bulk ICM flow induced in the merger. The cluster merger model of SCC destruction invokes low impact parameter infall as the condition required for core transformation. In contrast to this, the high angular momentum event occurring in Abell 1763 suggests that off-axis mergers play a greater role in establishing the non-cool core cluster population than previously assumed.
The Recent Growth History of the Fornax Cluster Derived from Simultaneous Sloshing and Gas Stripping: Simulating the Infall of NGC 1404Sheardown, AlexRoediger, ElkeSu, YuanyuanKraft, Ralph P.Fish, ThomasZuHone, John A.Forman, William R.Jones, ChristineChurazov, EugeneNulsen, Paul E. J.DOI: info:10.3847/1538-4357/aadc0fv. 865118
Sheardown, Alex, Roediger, Elke, Su, Yuanyuan, Kraft, Ralph P., Fish, Thomas, ZuHone, John A., Forman, William R., Jones, Christine, Churazov, Eugene, and Nulsen, Paul E. J. 2018. "The Recent Growth History of the Fornax Cluster Derived from Simultaneous Sloshing and Gas Stripping: Simulating the Infall of NGC 1404." The Astrophysical Journal 865:118.
ID: 149397
Type: article
Authors: Sheardown, Alex; Roediger, Elke; Su, Yuanyuan; Kraft, Ralph P.; Fish, Thomas; ZuHone, John A.; Forman, William R.; Jones, Christine; Churazov, Eugene; Nulsen, Paul E. J.
Abstract: We derive the recent growth history of the Fornax Cluster, in particular the recent infall of the giant elliptical galaxy NGC 1404. We show, using a simple cluster minor merger simulation tailored to Fornax and NGC 1404, that a second or more likely third encounter between the two reproduces all the main merger features observed in both objects; we firmly exclude a first infall scenario. Our simulations reveal a consistent picture: NGC 1404 passed by NGC 1399 about 1.1–1.3 Gyr ago from the northeast to the southwest and is now almost at the point of its next encounter from the south. This scenario explains the sloshing patterns observed in Fornax—a prominent northern cold front and an inner southern cold front. This scenario also explains the truncated atmosphere, the gas-stripping radius of NGC 1404, and its faint gas tail. Independent of the exact history, we can make a number of predictions. A detached bow shock south of NGC 1404 should exist, which is a remnant of the galaxy’s previous infall at a distance from NGC 1404 between 450 and 750 kpc with an estimated Mach number between 1.3 and 1.5. The wake of NGC 1404 also lies south of the galaxy with enhanced turbulence and a slight enhancement in metallicity compared to the undisturbed regions of the cluster. Southwest of NGC 1404, there is likely evidence of old turbulence originating from the previous infall. No scenario predicts enhanced turbulence outside of the cold front northwest of the cluster center.
What Do the Hitomi Observations Tell Us About the Turbulent Velocities in the Perseus Cluster? Probing the Velocity Field with Mock ObservationsZuHone, J. A.Miller, E. D.Bulbul, E.Zhuravleva, I.DOI: info:10.3847/1538-4357/aaa4b3v. 853180
ZuHone, J. A., Miller, E. D., Bulbul, E., and Zhuravleva, I. 2018. "What Do the Hitomi Observations Tell Us About the Turbulent Velocities in the Perseus Cluster? Probing the Velocity Field with Mock Observations." The Astrophysical Journal 853:180.
ID: 145800
Type: article
Authors: ZuHone, J. A.; Miller, E. D.; Bulbul, E.; Zhuravleva, I.
Abstract: Hitomi made the first direct measurements of galaxy cluster gas motions in the Perseus cluster, which implied that its core is fairly "quiescent," with velocities less than ~200 km s-1, despite the presence of an active galactic nucleus and sloshing cold fronts. Building on previous work, we use synthetic Hitomi/X-ray Spectrometer (SXS) observations of the hot plasma of a simulated cluster with sloshing gas motions and varying viscosity to analyze its velocity structure in a similar fashion. We find that sloshing motions can produce line shifts and widths similar to those measured by Hitomi. We find these measurements are unaffected by the value of the gas viscosity, since its effects are only manifested clearly on angular scales smaller than the SXS ~1? PSF. The PSF biases the line shift of regions near the core as much as ~40-50 km s-1, so it is crucial to model this effect carefully. We also infer that if sloshing motions dominate the observed velocity gradient, Perseus must be observed from a line of sight that is somewhat inclined from the plane of these motions, but one that still allows the spiral pattern to be visible. Finally, we find that assuming isotropy of motions can underestimate the total velocity and kinetic energy of the core in our simulation by as much as ~60%. However, the total kinetic energy in our simulated cluster core is still less than 10% of the thermal energy in the core, in agreement with the Hitomi observations.
Gas Sloshing Regulates and Records the Evolution of the Fornax ClusterSu, YuanyuanNulsen, Paul E. J.Kraft, Ralph P.Roediger, ElkeZuHone, John A.Jones, ChristineForman, William R.Sheardown, AlexIrwin, Jimmy A.Randall, Scott W.DOI: info:10.3847/1538-4357/aa989ev. 85169
Su, Yuanyuan, Nulsen, Paul E. J., Kraft, Ralph P., Roediger, Elke, ZuHone, John A., Jones, Christine, Forman, William R., Sheardown, Alex, Irwin, Jimmy A., and Randall, Scott W. 2017. "Gas Sloshing Regulates and Records the Evolution of the Fornax Cluster." The Astrophysical Journal 851:69.
ID: 145647
Type: article
Authors: Su, Yuanyuan; Nulsen, Paul E. J.; Kraft, Ralph P.; Roediger, Elke; ZuHone, John A.; Jones, Christine; Forman, William R.; Sheardown, Alex; Irwin, Jimmy A.; Randall, Scott W.
Abstract: We present results of a joint Chandra and XMM-Newton analysis of the Fornax Cluster, the nearest galaxy cluster in the southern sky. Signatures of merger-induced gas sloshing can be seen in the X-ray image. We identify four sloshing cold fronts in the intracluster medium, residing at radii of 3 kpc (west), 10 kpc (northeast), 30 kpc (southwest), and 200 kpc (east). Despite spanning over two orders of magnitude in radius, all four cold fronts fall onto the same spiral pattern that wraps around the BCG NGC 1399, likely all initiated by the infall of NGC 1404. The most evident front is to the northeast, 10 kpc from the cluster center, which separates low-entropy high-metallicity gas and high-entropy low-metallicity gas. The metallicity map suggests that gas sloshing, rather than an AGN outburst, is the driving force behind the redistribution of the enriched gas in this cluster. The innermost cold front resides within the radius of the strong cool core. The sloshing timescale within the cooling radius, calculated from the Brunt–Väsälä frequency, is an order of magnitude shorter than the cooling time. It is plausible that gas sloshing is contributing to the heating of the cool core, provided that gas of different entropies can be mixed effectively via Kelvin–Helmholtz instability. The estimated age of the outermost front suggests that this is not the first infall of NGC 1404.