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Register a new userThe Luminosity-Temperature Relation at z=0.4 for Clusters of galaxies
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R.F. Mushotzky
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We have obtained the first large sample of accurate temperatures for clusters at z>0.14 from ASCA. We compare the luminosity temperature (L-T) distribution for these clusters with the low redshift sample of David et al (1993) and find that there is no evidence for evolution. We also find that the intrinsic variance in this relation is roughly constant with redshift. Additionally, there is no detectable change in the relationship of optical velocity dispersion to X-ray temperature with redshift. Most cosmological simulations driven primarily by gravity predict substantial changes in the L-T relation due to the recent rapid growth of clusters. Our results are consistent either with models in which the cluster core entropy is dominated by pre-heating, or with low Omega models in which cluster structure does not evolve strongly with time. The intrinsic variance in the L-T relation at a fixed redshift can be due a variety of possibilites e.g. a change in the baryonic fraction from cluster to cluster, variation in the fraction of the total energy in the system arising from shocks or supernova heating or variations in the emission measure distributions in multiphase gas.
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(abridged) We describe XMM-Newton Guaranteed Time observations of a sample of eight high redshift (0.45<z<0.62) clusters. The goal of these observations was to measure the luminosity and the temperature of the clusters to a precision of ~10%, leading to constraints on the possible evolution of the luminosity--temperature relation, and ultimately on the values of the matter density, Omega_M and, to a lesser extent, the cosmological constant Omega_L. The clusters were drawn from the SHARC and 160 Square Degree (160SD) ROSAT surveys. Here we describe our data analysis techniques and present, for the first time with XMM-Newton,Lx-Tx relation. For each of the eight clusters in the sample, we have measured total bolometric luminosities, performed beta-model fits to the radial surface profiles and made spectral fits to a single temperature isothermal model. We describe data analysis techniques that pay particular attention to background mitigation. Characterizing the Lx-Tx relation as Lx = L_{6} (T/6keV)^{alpha},we find L_{6}=16.8 +7.6/-5.2 10^{44} erg/s and alpha=2.7 +/-0.4 for a EdS H=50 cosmology at a typical redshift z =0.55. Comparing with the low redshift study by Markevitch, assuming L-T to evolve as (1+z)^A, we find A=0.68 +/-0.26 for the same cosmology and A=1.52 +0.26/-0.27 for a concordance cosmology. We conclude that there is now evidence from both XMM-Newton and Chandra for an evolutionary trend in the L-T relation. Our observations lend support to the robustness and completeness of the SHARC and 160SD surveys.
A luminosity-temperature relation for clusters of galaxies is derived. The two models used, take into account the angular momentum acquisition by the proto-structures during their expansion and collapse. The first one is a modification of the self-similar model (SSM) while the second one is a modification of the Punctuated Equilibria Model (Cavaliere et al. 1999). In both models the mass-temperature relation (M-T) used is based on the calculations of Del Popolo (2002b). We show that the above models lead, in X-rays, to a luminosity-temperature relation that scales as L propto T^5, at scale of groups, flattening to L propto T^3 for rich clusters and converging to L propto T^2 at higher temperatures. However a fundamental result of our paper is that the non-similarity in the L-T relation, can be explained by a simple model that takes into account the amount of the angular momentum of a proto-structure. This result is in disagreement with the widely accepted idea that the above non-similarity is due to non-gravitating processes as those of heating/cooling.
We analyzed the luminosity-temperature-mass of gas (L_{X} - T - M_{g}) relation for sample of galaxy clusters that have been observed by the Chandra satellite. We used 21 high-redshift clusters (0.4 < z < 1.4). We assumed a power-law relation between the X-ray luminosity of galaxy clusters and its temperature and redshift L_{X} ~ (1+z)^{A_{L_{X}T}}T^{beta_{L_{X}T}}. We obtained that for an Omega_{m} = 0.27 and Lambda = 0.73 universe, A_{L_{X}T} = 1.50 +/- 0.23, beta_{L_{X}T} = 2.55 +/- 0.07 (for 68% confidence level). Then, we found the evolution of M_{g} - T relation is small. We assumed a power-law relation in the form M_{g} ~ (1+z)^{A_{M_{g}T}}T^{beta_{M_{g}T}} also, and we obtained A_{M_{g}T} = -0.58 +/- 0.13 and beta_{M_{g}T} = 1.77 +/- 0.16. We also obtained the evolution in M_{g} - L_{X} relation, we can conclude that such relation has strong evolution for our cosmological parameters. We used M_{g} ~ (1+z)^{A_{M_{g}L_{X}}}L^{beta_{M_{g}L_{X}}} equation for assuming this relation and we found A_{M_{g}L_{X}} ~ -1.86 +/- 0.34 and beta_{M_{g}L_{X}} = 0.73 +/- 0.15 for Omega_{m} = 0.27 and Lambda = 0.73 universe. In overal, the clusters on big redshifts have much stronger evolution between correlations of luminosity, temperature and mass, then such correlations for clusters at small redshifts. We can conclude that such strong evolution in L_{X} - T - M_{g} correlations indicate that in the past the clusters have bigger temperature and higher luminosity.
The evolution of the properties of the hot gas that fills the potential well of galaxy clusters is poorly known, since models are unable to give robust predictions and observations lack a sufficient redshift leverage and are affected by selection effects. Here, with just two high redshift, z approx 1.8, clusters avoiding selection biases, we obtain a significant extension of the redshift range and we begin to constrain the possible evolution of the X-ray luminosity vs temperature relation. The two clusters, JKC041 at z=2.2 and ISCSJ1438+3414 at z=1.41, are respectively the most distant cluster overall, and the second most distant that can be used for studying scaling relations. Their location in the X-ray luminosity vs temperature plane, with an X-ray luminosity 5 times lower than expected, suggests at the 95 % confidence that the evolution of the intracluster medium has not been self-similar in the last three quarters of the Universe age. Our conclusion is reinforced by data on a third, X-ray selected, high redshift cluster, too faint for its temperature when compared to a sample of similarly selected objects. Our data suggest that non-gravitational effects, such as the baryon physics, influence the evolution of galaxy cluster. Precise knowledge of evolution is central for using galaxy clusters as cosmological probes in planned X-ray surveys such as WFXT or JDEM.
We present our discovery observations and analysis of RDCS1317+2911, z = 0.805, and RDCS1350+6007, z= 0.804, two clusters of galaxies identified through X-ray emission in the ROSAT Deep Cluster Survey (RDCS). We find a temperature of 3.7 +1.5 -0.9 keV and a bolometric luminosity of 8.2e43 +1.7e43 -1.6e43 erg/s for RDCS1317+2911, and a temperature of 4.9 +1.3 -0.9 keV and a bolometric luminosity of 4.1e44 +0.5e44 -0.4e44 erg/s for RDCS1350+6007. Our weak lensing analysis of RDCS1350+6007 confirms the general shape of the inner density profile but predicts twice the mass of the model based on the X-ray profile. We combine the X-ray luminosities and temperatures for RDCS clusters of galaxies with such measurements of other clusters at high redshift (z>0.7) and fit the luminosity-temperature relation. We find no statistically significant evolution in the slope or zero-point of this relation at a median of z=0.83. This result is in agreement with models of intracluster medium evolution with significant pre-heating or high initial entropy values. We discuss how low temperature, high redshift clusters of galaxies will allow us to improve on this result and announce the discovery of two such objects, CXOU J0910.1+5419 and CXOU J1316.9+2914.
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