The Experts below are selected from a list of 5598 Experts worldwide ranked by ideXlab platform
W B Mori - One of the best experts on this subject based on the ideXlab platform.
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self generated magnetic and electric fields at a mach 6 Shock front in a low density helium gas by dual angle proton radiography
Physical Review Letters, 2019Co-Authors: R Hua, S. C. Wilks, C. Mcguffey, Jwakyung Kim, M Sherlock, M Baillygrandvaux, F N Beg, H Wen, Archis Joglekar, W B MoriAbstract:Shocks are abundant both in astrophysical and laboratory systems. While the electric fields generated at Shock Fronts have recently attracted great attention, the associated self-generated magnetic field is rarely studied, despite its ability to significantly affect the Shock profile in the nonideal geometry where density and temperature gradients are not parallel. We report here the observation of a magnetic field at the front of a Mach ∼6 Shock propagating in a low-density helium gas system. Proton radiography from different projection angles not only confirms the magnetic field's existence, but also provides a quantitative measurement of the field strength in the range ∼5 to 7 T. X-ray spectrometry allowed inference of the density and temperature at the Shock front, constraining the plasma conditions under which the magnetic and electric fields are generated. Simulations with the particle-in-cell code lsp attribute the self-generation of the magnetic field to the Biermann battery effect (∇n_{e}×∇T_{e}).
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self generated magnetic and electric fields at a mach 6 Shock front in a low density helium gas by dual angle proton radiography
Physical Review Letters, 2019Co-Authors: R Hua, S. C. Wilks, C. Mcguffey, M Sherlock, M Baillygrandvaux, F N Beg, H Wen, Archis Joglekar, Joungmok Kim, W B MoriAbstract:Shocks are abundant both in astrophysical and laboratory systems. While the electric fields generated at Shock Fronts have recently attracted great attention, the associated self-generated magnetic field is rarely studied, despite its ability to significantly affect the Shock profile in the nonideal geometry where density and temperature gradients are not parallel. We report here the observation of a magnetic field at the front of a Mach $\ensuremath{\sim}6$ Shock propagating in a low-density helium gas system. Proton radiography from different projection angles not only confirms the magnetic field's existence, but also provides a quantitative measurement of the field strength in the range $\ensuremath{\sim}5$ to 7 T. X-ray spectrometry allowed inference of the density and temperature at the Shock front, constraining the plasma conditions under which the magnetic and electric fields are generated. Simulations with the particle-in-cell code lsp attribute the self-generation of the magnetic field to the Biermann battery effect ($\ensuremath{\nabla}{n}_{e}\ifmmode\times\else\texttimes\fi{}\ensuremath{\nabla}{T}_{e}$).
P E J Nulsen - One of the best experts on this subject based on the ideXlab platform.
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Shock Fronts electron ion equilibration and intracluster medium transport processes in the merging cluster abell 2146
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: H R Russell, B R Mcnamara, J S Sanders, A C Fabian, P E J Nulsen, R E A Canning, S A BaumAbstract:We present a new 400-ks Chandra X-ray observation of the merging galaxy cluster Abell 2146. This deep observation reveals detailed structure associated with the major merger event including the Mach number M= 2.3 ± 0.2 bow Shock ahead of the dense, ram pressure stripped subcluster core and the first known example of an upstream Shock in the intracluster medium (ICM) (M= 1.6 ± 0.1). By measuring the electron temperature profile behind each Shock front, we determine the time-scale for the electron population to thermally equilibrate with the Shock-heated ions. We find that the temperature profile behind the bow Shock is consistent with the time-scale for Coulomb collisional equilibration and the post-Shock temperature is lower than expected for instant Shock heating of the electrons. Although like the Bullet cluster the electron temperatures behind the upstream Shock front are hotter than expected, favouring the instant heating model, the uncertainty on the temperature values is greater here and there is significant substructure complicating the interpretation. We also measured the width of each Shock front and the contact discontinuity on the leading edge of the subcluster core to investigate the suppression of transport processes in the ICM. The upstream Shock is ∼440 kpc in length but appears remarkably narrow over this distance with a best-fitting width of only 6+5−3 kpc compared with the mean free path of 23 ± 5 kpc. The leading edge of the subcluster core is also narrow with an upper limit on the width of only 2 kpc separating the cool, multiphase gas at 0.5–2 keV from the Shock-heated surrounding ICM at ∼6 keV. The strong suppression of diffusion and conduction across this edge suggests a magnetic draping layer may have formed around the subcluster core. The deep Chandra observation has also revealed a cool, dense plume of material extending ∼170 kpc perpendicular to the merger axis, which is likely to be the disrupted remnant of the primary cluster core. This asymmetry in the cluster morphology indicates the merger has a non-zero impact parameter. We suggest that this also explains why the south-western edge of the subcluster core is narrow and stable over ∼150 kpc in length, but the north-eastern edge is broad and being stripped of material.
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heating hot atmospheres with active galactic nuclei
Annual Review of Astronomy and Astrophysics, 2007Co-Authors: B R Mcnamara, P E J NulsenAbstract:High resolution X-ray spectroscopy of the hot gas in galaxy clusters has shown that the gas is not cooling to low temperatures at the predicted rates of hundreds to thousands of solar masses per year. X-ray images have revealed giant cavities and Shock Fronts in the hot gas that provide a direct and relatively reliable means of measuring the energy injected into hot atmospheres by active galactic nuclei (AGN). Average radio jet powers are near those required to offset radiative losses and to suppress cooling in isolated giant elliptical galaxies, and in larger systems up to the richest galaxy clusters. This coincidence suggests that heating and cooling are coupled by feedback, which suppresses star formation and the growth of luminous galaxies. How jet energy is converted to heat and the degree to which other heating mechanisms are contributing, e.g., thermal conduction, are not well understood. Outburst energies require substantial late growth of supermassive black holes. Unless all of the ∼10 62 erg required to suppress star formation is deposited in the cooling regions of clusters, AGN outbursts must alter large-scale properties of the intracluster medium.
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the heating of gas in a galaxy cluster by x ray cavities and large scale Shock Fronts
Nature, 2005Co-Authors: B R Mcnamara, P E J Nulsen, M W Wise, D A Rafferty, C L Carilli, Craig L Sarazin, E L BlantonAbstract:Astronomers using the latest generation of orbiting X-ray observatories are making some surprising discoveries, one of which is the relatively slow rate of cooling of gas in the cores of galaxy clusters. The Chandra X-ray observatory is now routinely observing giant cavities in the centre of galaxy clusters, and these may hold the key to this phenomenon. The gaseous halo of the galaxy cluster MS0735.6+7421 has been found to contain two such cavities, caused by interaction between a radio source and the hot gas surrounding it. This is producing the most powerful radio outburst known, and sufficient heat to counteract the expected cooling. The most likely power source is a supermassive black hole. Most of the baryons in galaxy clusters reside between the galaxies in a hot, tenuous gas1. The densest gas in their centres should cool and accrete onto giant central galaxies at rates of 10–1,000 solar masses per year1. No viable repository for this gas, such as clouds or new stars, has been found1. New X-ray observations, however, have revealed far less cooling below X-ray temperatures than expected2, altering the previously accepted picture of cooling flows. As a result, most of the gas must be heated to and maintained at temperatures above ∼2 keV (ref. 3). The most promising heating mechanism is powerful radio jets emanating from supermassive black holes in the central galaxies of clusters4. Here we report the discovery of giant cavities and Shock Fronts in a distant (z = 0.22) cluster caused by an interaction between a radio source and the hot gas surrounding it. The energy involved is ∼6 × 1061 erg, the most powerful radio outburst known. This is enough energy to quench a cooling flow for several Gyr, and to provide ∼1/3 keV per particle of heat to the surrounding cluster.
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chandra observation of abell 2142 survival of dense subcluster cores in a merger
The Astrophysical Journal, 2000Co-Authors: Maxim Markevitch, P E J Nulsen, T Ponman, M W Bautz, D J Burke, Laurence P David, D S Davis, R H DonnellyAbstract:We use Chandra data to map the gas temperature in the central region of the merging cluster A2142. The cluster is markedly nonisothermal; it appears that the central cooling flow has been disturbed but not destroyed by a merger. The X-ray image exhibits two sharp, bow-shaped, Shocklike surface brightness edges or gas density discontinuities. However, temperature and pressure profiles across these edges indicate that these are not Shock Fronts. The pressure is reasonably continuous across these edges, while the entropy jumps in the opposite sense to that in a Shock (i.e., the denser side of the edge has lower temperature, and hence lower entropy). Most plausibly, these edges delineate the dense subcluster cores that have survived a merger and ram pressure stripping by the surrounding Shock-heated gas.
R Hua - One of the best experts on this subject based on the ideXlab platform.
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self generated magnetic and electric fields at a mach 6 Shock front in a low density helium gas by dual angle proton radiography
Physical Review Letters, 2019Co-Authors: R Hua, S. C. Wilks, C. Mcguffey, Jwakyung Kim, M Sherlock, M Baillygrandvaux, F N Beg, H Wen, Archis Joglekar, W B MoriAbstract:Shocks are abundant both in astrophysical and laboratory systems. While the electric fields generated at Shock Fronts have recently attracted great attention, the associated self-generated magnetic field is rarely studied, despite its ability to significantly affect the Shock profile in the nonideal geometry where density and temperature gradients are not parallel. We report here the observation of a magnetic field at the front of a Mach ∼6 Shock propagating in a low-density helium gas system. Proton radiography from different projection angles not only confirms the magnetic field's existence, but also provides a quantitative measurement of the field strength in the range ∼5 to 7 T. X-ray spectrometry allowed inference of the density and temperature at the Shock front, constraining the plasma conditions under which the magnetic and electric fields are generated. Simulations with the particle-in-cell code lsp attribute the self-generation of the magnetic field to the Biermann battery effect (∇n_{e}×∇T_{e}).
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self generated magnetic and electric fields at a mach 6 Shock front in a low density helium gas by dual angle proton radiography
Physical Review Letters, 2019Co-Authors: R Hua, S. C. Wilks, C. Mcguffey, M Sherlock, M Baillygrandvaux, F N Beg, H Wen, Archis Joglekar, Joungmok Kim, W B MoriAbstract:Shocks are abundant both in astrophysical and laboratory systems. While the electric fields generated at Shock Fronts have recently attracted great attention, the associated self-generated magnetic field is rarely studied, despite its ability to significantly affect the Shock profile in the nonideal geometry where density and temperature gradients are not parallel. We report here the observation of a magnetic field at the front of a Mach $\ensuremath{\sim}6$ Shock propagating in a low-density helium gas system. Proton radiography from different projection angles not only confirms the magnetic field's existence, but also provides a quantitative measurement of the field strength in the range $\ensuremath{\sim}5$ to 7 T. X-ray spectrometry allowed inference of the density and temperature at the Shock front, constraining the plasma conditions under which the magnetic and electric fields are generated. Simulations with the particle-in-cell code lsp attribute the self-generation of the magnetic field to the Biermann battery effect ($\ensuremath{\nabla}{n}_{e}\ifmmode\times\else\texttimes\fi{}\ensuremath{\nabla}{T}_{e}$).
Eric J Hallman - One of the best experts on this subject based on the ideXlab platform.
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galaxy cluster radio relics in adaptive mesh refinement cosmological simulations relic properties and scaling relationships
The Astrophysical Journal, 2011Co-Authors: Samuel W Skillman, Eric J Hallman, Brian W Oshea, Jack O Burns, Britton D Smith, Matthew J TurkAbstract:Cosmological Shocks are a critical part of large-scale structure formation, and are responsible for heating the intracluster medium in galaxy clusters. In addition, they are capable of accelerating non-thermal electrons and protons. In this work, we focus on the acceleration of electrons at Shock Fronts, which is thought to be responsible for radio relics—extended radio features in the vicinity of merging galaxy clusters. By combining high-resolution adaptive mesh refinement/N-body cosmological simulations with an accurate Shock-finding algorithm and a model for electron acceleration, we calculate the expected synchrotron emission resulting from cosmological structure formation. We produce synthetic radio maps of a large sample of galaxy clusters and present luminosity functions and scaling relationships. With upcoming long-wavelength radio telescopes, we expect to see an abundance of radio emission associated with merger Shocks in the intracluster medium. By producing observationally motivated statistics, we provide predictions that can be compared with observations to further improve our understanding of magnetic fields and electron Shock acceleration.
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galaxy cluster radio relics in adaptive mesh refinement cosmological simulations relic properties and scaling relationships
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Samuel W Skillman, Eric J Hallman, Brian W Oshea, Jack O Burns, Britton D Smith, Matthew J TurkAbstract:Cosmological Shocks are a critical part of large-scale structure formation, and are responsible for heating the intracluster medium in galaxy clusters. In addition, they are also capable of accelerating non-thermal electrons and protons. In this work, we focus on the acceleration of electrons at Shock Fronts, which is thought to be responsible for radio relics - extended radio features in the vicinity of merging galaxy clusters. By combining high resolution AMR/N-body cosmological simulations with an accurate Shock finding algorithm and a model for electron acceleration, we calculate the expected synchrotron emission resulting from cosmological structure formation. We produce synthetic radio maps of a large sample of galaxy clusters and present luminosity functions and scaling relationships. With upcoming long wavelength radio telescopes, we expect to see an abundance of radio emission associated with merger Shocks in the intracluster medium. By producing observationally motivated statistics, we provide predictions that can be compared with observations to further improve our understanding of magnetic fields and electron Shock acceleration.
E L Blanton - One of the best experts on this subject based on the ideXlab platform.
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the heating of gas in a galaxy cluster by x ray cavities and large scale Shock Fronts
Nature, 2005Co-Authors: B R Mcnamara, P E J Nulsen, M W Wise, D A Rafferty, C L Carilli, Craig L Sarazin, E L BlantonAbstract:Astronomers using the latest generation of orbiting X-ray observatories are making some surprising discoveries, one of which is the relatively slow rate of cooling of gas in the cores of galaxy clusters. The Chandra X-ray observatory is now routinely observing giant cavities in the centre of galaxy clusters, and these may hold the key to this phenomenon. The gaseous halo of the galaxy cluster MS0735.6+7421 has been found to contain two such cavities, caused by interaction between a radio source and the hot gas surrounding it. This is producing the most powerful radio outburst known, and sufficient heat to counteract the expected cooling. The most likely power source is a supermassive black hole. Most of the baryons in galaxy clusters reside between the galaxies in a hot, tenuous gas1. The densest gas in their centres should cool and accrete onto giant central galaxies at rates of 10–1,000 solar masses per year1. No viable repository for this gas, such as clouds or new stars, has been found1. New X-ray observations, however, have revealed far less cooling below X-ray temperatures than expected2, altering the previously accepted picture of cooling flows. As a result, most of the gas must be heated to and maintained at temperatures above ∼2 keV (ref. 3). The most promising heating mechanism is powerful radio jets emanating from supermassive black holes in the central galaxies of clusters4. Here we report the discovery of giant cavities and Shock Fronts in a distant (z = 0.22) cluster caused by an interaction between a radio source and the hot gas surrounding it. The energy involved is ∼6 × 1061 erg, the most powerful radio outburst known. This is enough energy to quench a cooling flow for several Gyr, and to provide ∼1/3 keV per particle of heat to the surrounding cluster.