اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMulti-fluid shocks in clusters of galaxies: entropy, sigma_ v-T, M-T and L_x-T scalings
66
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The nonthermal phenomena in clusters of galaxies are considered in the context of the hierarchical model of cosmic structure formation by accretion and merging of the dark matter (DM) substructures.Accretion and merging processes produce large-scale gas shocks. The plasma shocks are expected to be collisionless. In the course of clusters aggregation, the shocks, being the main gas-heating agent, generate turbulent magnetic fields and accelerate energetic particles via collisionless multi-fluid plasma relaxation processes. The intracluster gas heating and entropy production rate by a collisionless shock may differ significantly from that in a single-fluid collisional shock. Simple scaling relations for postshock ion temperature and entropy as functions of shock velocity in strong collisionless multi-fluid shocks are presented. We show that the multi-fluid nature of the collisionless shocks results in high gas compression, reduced entropy production and modified sigma_v-T, M-T and L_x-T scalings. The scaling indexes estimated for a simple model of a strong accretion multi-fluid shock are generally consistent with observations. Soft X-ray and extreme ultraviolet photons dominate the emission of strong accretion shock precursors that appear as large-scale filaments. Magnetic fields, turbulence and energetic particles constitute the nonthermal components contributing into the pressure balance, energy transport and emission of clusters. Nonthermal emission of energetic particles could be a test to constrain the cluster properties.
قيم البحث
اقرأ أيضاً
In this paper based on ROSAT/PSPC data we investigate the emission measure profiles of a sample of hot clusters of galaxies (kT>3.5keV) in order to explain the differences between observed and theoretically predicted L_X-T relation. Looking at the fo
rm of the emission measure profiles as well as their normalizations we find clear indication that indeed the profiles have similar shapes once scaled to the virial radius, however, the normalization of the profiles shows a strong temperature dependence. We introduce a M_gas-T relation with the dependence M_gas propto T^1.94. This relationship explains the observed L_X-T relation and reduces the scatter in the scaled profiles by a factor of 2 when compared to the classical scaling. We interpret this finding as strong indication that the M_gas-T relation in clusters deviates from classical scaling.
We derive the geodesic equation for determining the Ryu-Takayanagi surface in $AdS_3$ deformed by single trace $mu T bar T + varepsilon_+ J bar T + varepsilon_- T bar J$ deformation for generic values of $(mu, varepsilon_+, varepsilon_-)$ for which t
he background is free of singularities. For generic values of $varepsilon_pm$, Lorentz invariance is broken, and the Ryu-Takayanagi surface embeds non-trivially in time as well as spatial coordinates. We solve the geodesic equation and characterize the UV and IR behavior of the entanglement entropy and the Casini-Huerta $c$-function. We comment on various features of these observables in the $(mu, varepsilon_+, varepsilon_-)$ parameter space. We discuss the matching at leading order in small $(mu, varepsilon_+, varepsilon_-)$ expansion of the entanglement entropy between the single trace deformed holographic system and a class of double trace deformed theories where a strictly field theoretic analysis is possible. We also comment on expectation value of a large rectangular Wilson loop-like observable.
In this paper we re-visit the observational relation between X-ray luminosity and temperature for high-z galaxy clusters and compare it with the local L_X-T and with theoretical models. To these ends we use a sample of 17 clusters extracted from the
Chandra archive supplemented with additional clusters from the literature, either observed by Chandra or XMM-Newton, to form a final sample of 39 high redshift (0.25 < z < 1.3) objects. Different statistical approaches are adopted to analyze the L_X-T relation. The slope of the L_X-T relation of high redshift clusters is steeper than expected from the self-similar model predictions and steeper, even though still compatible within the errors, than the local L_X-T slope. The distant cluster L_X-T relation shows a significant evolution with respect to the local Universe: high-z clusters are more luminous than the local ones by a factor ~2 at any given temperature. The evolution with redshift of the L_X-T relation cannot be described by a single power law nor by the evolution predicted by the self-similar model. We find a strong evolution, similar or stronger than the self-similar model, from z = 0 to z <0.3 followed by a much weaker, if any, evolution at higher redshift. The weaker evolution is compatible with non-gravitational models of structure formation. According to us a statistically significant sample of nearby clusters (z < 0.25) should be observed with the current available X-ray telescopes to completely exclude observational effects due to different generation detectors and to understand this novel result.
The relation between X-ray luminosity (L_X) and ambient gas temperature (T) among massive galactic systems is an important cornerstone of both observational cosmology and galaxy-evolution modeling. In the most massive galaxy clusters, the relation is
determined primarily by cosmological structure formation. In less massive systems, it primarily reflects the feedback response to radiative cooling of circumgalactic gas. Here we present a simple but powerful model for the L_X-T relation as a function of physical aperture R within which those measurements are made. The model is based on the precipitation framework for AGN feedback and assumes that the circumgalactic medium is precipitation-regulated at small radii and limited by cosmological structure formation at large radii. We compare this model with many different data sets and show that it successfully reproduces the slope and upper envelope of the L_X-T-R relation over the temperature range from ~0.2 keV through >10 keV. Our findings strongly suggest that the feedback mechanisms responsible for regulating star formation in individual massive galaxies have much in common with the precipitation-triggered feedback that appears to regulate galaxy-cluster cores.
We present four infinite series of new quantum theories with super-Poincare symmetry in six dimensions, which are not local quantum field theories. They have string like excitations but the string coupling is of order one. Compactifying these theorie
s on $T^5$ we find a Matrix theory description of M theory on $T^5$ and on $T^5/IZ_2$, which is well defined and is manifestly U-duality invariant.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
