All-Electron Path Integral Monte Carlo Simulations of Warm Dense Matter: Application to Water and Carbon Plasmas

We develop an all-electron path integral Monte Carlo (PIMC) method with free-particle nodes for warm dense matter and apply it to water and carbon plasmas. We thereby extend PIMC studies beyond hydrogen and helium to elements with core electrons. PIMC pressures, internal energies, and pair-correlation functions compare well with density functional theory molecular dynamics (DFT-MD) at temperatures of (2.5-7.5)$\times10^5$ K and both methods together form a coherent equation of state (EOS) over a density-temperature range of 3--12 g/cm$^3$ and 10$^4$--10$^9$ K

A Lensed Arc in the Low Redshift Cluster Abell 2124

We report the discovery of an arc-like object 27" from the center of the cD galaxy in the redshift $z=0.066$ cluster A2124. Observations with the Keck II telescope reveal that the object is a background galaxy at $z=0.573$, apparently lensed into an arc of length \sim 8 \farcs5 and total R magnitude $m_R = 20.86\pm0.07$. The width of the arc is resolved; we estimate it to be $\sim$0\farcs6 after correcting for seeing. A lens model of the A2124 core mass distribution consistent with the cluster galaxy velocity dispersion reproduces the observed arc geometry and indicates a magnification factor \gta 9. With this magnification, the strength of the [OII] \lambda 3727 line implies a star-formation rate of SFR \sim 0.4 h^{-2}\msun yr^{-1}$. A2124 thus appears to be the lowest redshift cluster known to exhibit strong lensing of a distant background galaxy.Comment: 6 pages using emulateapj.sty; 4 Postscript figures; Figure 4 uses color. Accepted for publication, but ApJ Letters' new policy of counting data images makes the manuscript too long; will appear in main journal. This final version has minor correction

A Classical Density-Functional Theory for Describing Water Interfaces

We develop a classical density functional for water which combines the White Bear fundamental-measure theory (FMT) functional for the hard sphere fluid with attractive interactions based on the Statistical Associating Fluid Theory (SAFT-VR). This functional reproduces the properties of water at both long and short length scales over a wide range of temperatures, and is computationally efficient, comparable to the cost of FMT itself. We demonstrate our functional by applying it to systems composed of two hard rods, four hard rods arranged in a square and hard spheres in water

Thermodynamics of hot dense H-plasmas: Path integral Monte Carlo simulations and analytical approximations

This work is devoted to the thermodynamics of high-temperature dense hydrogen plasmas in the pressure region between $10^{-1}$ and $10^2$ Mbar. In particular we present for this region results of extensive calculations based on a recently developed path integral Monte Carlo scheme (direct PIMC). This method allows for a correct treatment of the thermodynamic properties of hot dense Coulomb systems. Calculations were performed in a broad region of the nonideality parameter $\Gamma \lesssim 3$ and degeneracy parameter $n_e \Lambda^3 \lesssim 10$. We give a comparison with a few available results from other path integral calculations (restricted PIMC) and with analytical calculations based on Pade approximations for strongly ionized plasmas. Good agreement between the results obtained from the three independent methods is found.Comment: RevTex file, 21 pages, 5 ps-figures include

The WARPS survey: III. The discovery of an X-ray luminous galaxy cluster at z=0.833 and the impact of X-ray substructure on cluster abundance measurements

The WARPS team reviews the properties and history of discovery of ClJ0152.7-1357, an X-ray luminous, rich cluster of galaxies at z=0.833. At L_X = 8 x 10^44 h^(-2) erg/s (0.5-2.0 keV) ClJ0152.7-1357 is the most X-ray luminous cluster known at redshifts z>0.55. The high X-ray luminosity of the system suggests that massive clusters may begin to form at redshifts considerably greater than unity. This scenario is supported by the high degree of optical and X-ray substructure in ClJ0152.7-1357, which is similarly complex as that of other X-ray selected distant clusters and consistent with the picture of cluster formation by mass infall along large-scale filaments. X-ray emission from ClJ0152.7-1357 was detected already in 1980 with the EINSTEIN IPC. However, because the complex morphology of the emission caused its significance to be underestimated, the corresponding source was not included in the EMSS cluster sample and hence not previously identified. Simulations of the EMSS source detection and selection procedure suggest a general bias of the EMSS against X-ray luminous clusters with pronounced substructure. If highly unrelaxed, merging clusters are common at high redshift, they could create a bias in some samples as the morphological complexity of mergers may cause them to fall below the flux limit of surveys that assume a unimodal spatial source geometry. Conversely, the enhanced X-ray luminosity of mergers might cause them to, temporarily, rise above the flux limit. Either effect could lead to erroneous conclusions about the evolution of the comoving cluster space density. A high fraction of morphologically complex clusters at high redshift would also call into question the validity of cosmological studies that assume that the systems under investigation are virialized.Comment: 17 pages, 7 figures; revised to focus on possible detection biases caused by substructure in clusters; accepted for publication in ApJ; uses emulateapj.sty; eps files of figures 1 and 2 can be obtained from ftp://hubble.ifa.hawaii.edu/pub/ebeling/warp

ROSAT PSPC Observations of the Richest (R≥2R \geq 2) ACO Clusters

We have compiled an X-ray catalog of optically selected rich clusters of galaxies observed by the PSPC during the pointed GO phase of the ROSAT mission. This paper contains a systematic X-ray analysis of 150 clusters with an optical richness classification of $R \geq 2$ from the ACO catalog (Abell, Corwin, and Olowin 1989). All clusters were observed within 45' of the optical axis of the telescope during pointed PSPC observations. For each cluster, we calculate: the net 0.5-2.0 keV PSPC count rate (or $4 \sigma$ upper limit) in a 1 Mpc radius aperture, 0.5-2.0 keV flux and luminosity, bolometric luminosity, and X-ray centroid. The cluster sample is then used to examine correlations between the X-ray and optical properties of clusters, derive the X-ray luminosity function of clusters with different optical classifications, and obtain a quantitative estimate of contamination (i.e, the fraction of clusters with an optical richness significantly overestimated due to interloping galaxies) in the ACO catalog

Path integral Monte Carlo calculations of helium and hydrogen-helium plasma thermodynamics and of the deuterium shock Hugoniot

In this work we calculate the thermodynamic properties of hydrogen-helium plasmas with different mass fractions of helium by the direct path integral Monte Carlo method. To avoid unphysical approximations we use the path integral representation of the density matrix. We pay special attention to the region of weak coupling and degeneracy and compare the results of simulation with a model based on the chemical picture. Further with the help of calculated deuterium isochors we compute the shock Hugoniot of deuterium. We analyze our results in comparison with recent experimental and calculated data on the deuterium Hugoniot.Comment: 7 pages, 5 Postscript figures, accepted for publication in J. Phys. A: Math. Ge

Reconstruction of a first-order phase transition from computer simulations of individual phases and subphases

We present a new method for investigating first-order phase transitions using Monte Carlo simulations. It relies on the multiple-histogram method and uses solely histograms of individual phases. In addition, we extend the method to include histograms of subphases. The free energy difference between phases, necessary for attributing the correct statistical weights to the histograms, is determined by a detour in control parameter space via auxiliary systems with short relaxation times. We apply this method to a recently introduced model for structure formation in polypeptides for which other methods fail.Comment: 13 pages in preprint mode, REVTeX, 2 Figures available from the authors ([email protected], [email protected]

Constraining the redshift evolution of the Cosmic Microwave Background black-body temperature with PLANCK data

We constrain the deviation of adiabatic evolution of the Universe using the data on the Cosmic Microwave Background (CMB) temperature anisotropies measured by the {\it Planck} satellite and a sample of 481 X-ray selected clusters with spectroscopically measured redshifts. To avoid antenna beam effects, we bring all the maps to the same resolution. We use a CMB template to subtract the cosmological signal while preserving the Thermal Sunyaev-Zeldovich (TSZ) anisotropies; next, we remove galactic foreground emissions around each cluster and we mask out all known point sources. If the CMB black-body temperature scales with redshift as $T(z)=T_0(1+z)^{1-\alpha}$, we constrain deviations of adiabatic evolution to be $\alpha=-0.007\pm 0.013$, consistent with the temperature-redshift relation of the standard cosmological model. This result could suffer from a potential bias $\delta\alpha$ associated with the CMB template, that we quantify it to be $|\delta\alpha|\le 0.02$ and with the same sign than the measured value of $\alpha$, but is free from those biases associated with using TSZ selected clusters; it represents the best constraint to date of the temperature-redshift relation of the Big-Bang model using only CMB data, confirming previous results.Comment: ApJ, in press. Manuscript matches the accepted version: 10 pages, 7 figures, 3 table

Measurements of Sunyaev-Zel'dovich Effect Scaling Relations for Clusters of Galaxies

We present new measurements of the Sunyaev-Zel'dovich (SZ) effect from clusters of galaxies using the Sunyaev-Zel'dovich Infrared Experiment (SuZIE II). We combine these new measurements with previous cluster observations with the SuZIE instrument to form a sample of 15 clusters of galaxies. For this sample we calculate the central Comptonization, y, and the integrated SZ flux decrement, S, for each of our clusters. We find that the integrated SZ flux is a more robust observable derived from our measurements than the central Comptonization due to inadequacies in the spatial modelling of the intra-cluster gas with a standard Beta model. This is highlighted by comparing our central Comptonization results with values calculated from measurements using the BIMA and OVRO interferometers. On average, the SuZIE calculated central Comptonizations are approximately 60% higher in the cooling flow clusters than the interferometric values, compared to only approximately 12% higher in the non-cooling flow clusters. We believe this discrepancy to be in large part due to the spatial modelling of the intra-cluster gas. From our cluster sample we construct y-T and S-T scaling relations. The y-T scaling relation is inconsistent with what we would expect for self-similar clusters; however this result is questionable because of the large systematic uncertainty in the central Comptonization. The S-T scaling relation has a slope and redshift evolution consistent with what we expect for self-similar clusters with a characteristic density that scales with the mean density of the universe. We rule out zero redshift evolution of the S-T relation at 90% confidence.Comment: Accepted to Astrophysical Journal. 52 pages, 14 tables, 7 figures ;replaced to match ApJ accepted versio