WorldWideScience

Sample records for chandra cluster cosmology

  1. Cosmological constraints from Chandra observations of galaxy clusters.

    Science.gov (United States)

    Allen, Steven W

    2002-09-15

    Chandra observations of rich, relaxed galaxy clusters allow the properties of the X-ray gas and the total gravitating mass to be determined precisely. Here, we present results for a sample of the most X-ray luminous, dynamically relaxed clusters known. We show that the Chandra data and independent gravitational lensing studies provide consistent answers on the mass distributions in the clusters. The mass profiles exhibit a form in good agreement with the predictions from numerical simulations. Combining Chandra results on the X-ray gas mass fractions in the clusters with independent measurements of the Hubble constant and the mean baryonic matter density in the Universe, we obtain a tight constraint on the mean total matter density of the Universe, Omega(m), and an interesting constraint on the cosmological constant, Omega(Lambda). We also describe the 'virial relations' linking the masses, X-ray temperatures and luminosities of galaxy clusters. These relations provide a key step in linking the observed number density and spatial distribution of clusters to the predictions from cosmological models. The Chandra data confirm the presence of a systematic offset of ca. 40% between the normalization of the observed mass-temperature relation and the predictions from standard simulations. This finding leads to a significant revision of the best-fit value of sigma(8) inferred from the observed temperature and luminosity functions of clusters.

  2. Chandra Cluster Cosmology Project III: Cosmological Parameter Constraints

    DEFF Research Database (Denmark)

    Vikhlinin, A.; Kravtsov, A. V.; Burenin, R. A.;

    2009-01-01

    detected in the All-Sky Survey. Evolution of the mass function between these redshifts requires ΩΛ > 0 with a ~5σ significance, and constrains the dark energy equation-of-state parameter to w 0 = –1.14 ± 0.21, assuming a constant w and a flat universe. Cluster information also significantly improves...

  3. Chandra Cluster Cosmology Project. II. Samples and X-Ray Data Reduction

    DEFF Research Database (Denmark)

    Vikhlinin, A.; Burenin, R. A.; Ebeling, H.;

    2009-01-01

    of relations between the total cluster mass and its X-ray indicators (TX , M gas, and YX ) based on a subsample of low-z relaxed clusters, and present a first measurement of the evolving LX -M tot relation (with M tot estimated from YX ) obtained from a well defined statistically complete cluster sample......We discuss the measurements of the galaxy cluster mass functions at z ≈ 0.05 and z ≈ 0.5 using high-quality Chandra observations of samples derived from the ROSAT PSPC All-Sky and 400 deg2 surveys. We provide a full reference for the data analysis procedures, present updated calibration...... at a fixed mass threshold, e.g., by a factor of 5.0 ± 1.2 at M 500 = 2.5 × 1014 h –1 M sun between z = 0 and 0.5. This evolution reflects the growth of density perturbations, and can be used for the cosmological constraints complementing those from the distance-redshift relation....

  4. Reconciling Planck cluster counts and cosmology: Chandra/XMM instrumental calibration and hydrostatic mass bias

    CERN Document Server

    Israel, Holger; Nevalainen, Jukka; Massey, Richard; Reiprich, Thomas

    2014-01-01

    The temperature of X-ray emitting gas $T_X$ is often used to infer the total mass of galaxy clusters (under the assumption of hydrostatic equilibrium). Unfortunately, XMM-Newton and Chandra observatories measure inconsistent temperatures for the same gas, due to uncertain instrumental calibration. We translate the relative bias in $T_X$ measurements of Schellenberger et al. (2014) into a bias on inferred mass for a sample of clusters with homogeneous weak lensing (WL) masses, to simultaneously examine the hydrostatic bias and instrument calibration. Israel et al. (2014) found consistent WL and Chandra hydrostatic X-ray masses for a sample of clusters at $z$~0.5 and masses of a few $10^{14}$ $M_{\\odot}$. We find their XMM-Newton masses to be lower by $b^{xcal}=15$-$20$ % than their Chandra masses. At the massive end ($>5\\cdot 10^{14}$ $M_{\\odot}$), the XMM-Newton masses are ~35% lower than the WL masses. Assuming that the true hydrostatic bias is 20 %, as indicated by simulations, our results for the massive e...

  5. Galaxy Clusters with Chandra

    CERN Document Server

    Forman, W; Markevitch, M L; Vikhlinin, A A; Churazov, E

    2002-01-01

    We discuss Chandra results related to 1) cluster mergers and cold fronts and 2) interactions between relativistic plasma and hot cluster atmospheres. We describe the properties of cold fronts using NGC1404 in the Fornax cluster and A3667 as examples. We discuss multiple surface brightness discontinuities in the cooling flow cluster ZW3146. We review the supersonic merger underway in CL0657. Finally, we summarize the interaction between plasma bubbles produced by AGN and hot gas using M87 and NGC507 as examples.

  6. XMM-Newton and Chandra Cross Calibration Using HIFLUGCS Galaxy Clusters: Systematic Temperature Differences and Cosmological Impact

    OpenAIRE

    Schellenberger, G.; Reiprich, T. H.; Lovisari, L.; Nevalainen, J.; David, L

    2014-01-01

    Cosmological constraints from clusters rely on accurate gravitational mass estimates, which strongly depend on cluster gas temperature measurements. Therefore, systematic calibration differences may result in biased, instrument-dependent cosmological constraints. This is of special interest in the light of the tension between the Planck results of the primary temperature anisotropies of the CMB and Sunyaev-Zel'dovich plus X-ray cluster counts analyses. We quantify in detail the systematics an...

  7. Cosmology with X-ray Cluster Baryons

    Energy Technology Data Exchange (ETDEWEB)

    Linder, Eric V.

    2007-04-10

    X-ray cluster measurements interpreted with a universal baryon/gas mass fraction can theoretically serve as a cosmological distance probe. We examine issues of cosmological sensitivity for current (e.g., Chandra X-ray Observatory, XMM-Newton) and next generation (e.g., Con-X, XEUS) observations, along with systematic uncertainties and biases. To give competitive next generation constraints on dark energy, we find that systematics will need to be controlled to better than 1percent and any evolution in f_gas (and other cluster gas properties) must be calibrated so the residual uncertainty is weaker than (1+z)0.03.

  8. Cosmology and astrophysics from relaxed galaxy clusters - II. Cosmological constraints

    Science.gov (United States)

    Mantz, A. B.; Allen, S. W.; Morris, R. G.; Rapetti, D. A.; Applegate, D. E.; Kelly, P. L.; von der Linden, A.; Schmidt, R. W.

    2014-05-01

    This is the second in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. The data set employed here consists of Chandra observations of 40 such clusters, identified in a comprehensive search of the Chandra archive for hot (kT ≳ 5 keV), massive, morphologically relaxed systems, as well as high-quality weak gravitational lensing data for a subset of these clusters. Here we present cosmological constraints from measurements of the gas mass fraction, fgas, for this cluster sample. By incorporating a robust gravitational lensing calibration of the X-ray mass estimates, and restricting our measurements to the most self-similar and accurately measured regions of clusters, we significantly reduce systematic uncertainties compared to previous work. Our data for the first time constrain the intrinsic scatter in fgas, 7.4 ± 2.3 per cent in a spherical shell at radii 0.8-1.2 r2500 (˜1/4 of the virial radius), consistent with the expected level of variation in gas depletion and non-thermal pressure for relaxed clusters. From the lowest redshift data in our sample, five clusters at z 1, we obtain consistent results for Ωm and interesting constraints on dark energy: Ω _{{Λ }}=0.65^{+0.17}_{-0.22}> for non-flat ΛCDM (cosmological constant) models, and w = -0.98 ± 0.26 for flat models with a constant dark energy equation of state. Our results are both competitive and consistent with those from recent cosmic microwave background, Type Ia supernova and baryon acoustic oscillation data. We present constraints on more complex models of evolving dark energy from the combination of fgas data with these external data sets, and comment on the possibilities for improved fgas constraints using current and next-generation X-ray observatories and lensing data.

  9. Cosmology with clusters of galaxies

    CERN Document Server

    Bahcall, Neta A

    1995-01-01

    Rich clusters of galaxies, the largest virialized systems known, provide a powerful tool for the study of cosmology. Some of the fundamental questions that can be addressed with clusters of galaxies include: how did galaxies and large-scale structure form and evolve? What is the amount, composition and distribution of matter in the universe? I review some of the studies utilizing clusters of galaxies to investigare, among others: - The dark matter on clusters scale and the mean mass-density of the universe; - The large-scale structure of the universe; - The peculiar velocity field on large scales; - The mass-function of groups and clusters of galaxies; - The constraints placed on specific cosmological models using the cluster data.

  10. Cosmology and Astrophysics from Relaxed Galaxy Clusters I: Sample Selection

    CERN Document Server

    Mantz, Adam B; Morris, R Glenn; Schmidt, Robert W; von der Linden, Anja; Urban, Ondrej

    2015-01-01

    This is the first in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here we present a new, automated method for identifying relaxed clusters based on their morphologies in X-ray imaging data. While broadly similar to others in the literature, the morphological quantities that we measure are specifically designed to provide a fair basis for comparison across a range of data quality and cluster redshifts, to be robust against missing data due to point-source masks and gaps between detectors, and to avoid strong assumptions about the cosmological background and cluster masses. Based on three morphological indicators - Symmetry, Peakiness and Alignment - we develop the SPA criterion for relaxation. This analysis was applied to a large sample of cluster observations from the Chandra and ROSAT archives. Of the 361 clusters which received the SPA treatment, 57 (16 per cent) were subsequently found to be relaxed according to our criterion. We compare our me...

  11. Cosmology with cluster surveys

    Indian Academy of Sciences (India)

    Subhabrata Majumdar

    2004-10-01

    Surveys of clusters of galaxies provide us with a powerful probe of the density and nature of the dark energy. The red-shift distribution of detected clusters is highly sensitive to the dark energy equation of state parameter . Upcoming Sunyaev–Zel'dovich (SZ) surveys would provide us large yields of clusters to very high red-shifts. Self-calibration of cluster scaling relations, possible for such a huge sample, would be able to constrain systematic biases on mass estimators. Combining cluster red-shift abundance with limited mass follow-up and cluster mass power spectrum can then give constraints on , as well as on 8 and to a few per cents.

  12. HIGH-Z X-RAY AGN CLUSTERING & COSMOLOGICAL INFERENCE

    Directory of Open Access Journals (Sweden)

    M. Plionis

    2009-01-01

    Full Text Available We study the angular clustering of X-ray selected active galactic nuclei (AGN in di erent ux-limited sub- samples of the Chandra Deep Field North (CDF-N and South (CDF-S surveys. We nd a strong dependence of the clustering strength on the sub-sample ux-limit, a fact which explains most of the disparate clustering results of di erent XMM and Chandra surveys. At high ux-limits the clustering length increases considerably; for example, at fx;limit 1015 erg s-1 cm-2, we obtain r0 ' 17 5 and 18 3 h-1 Mpc, for the CDF-N and CDF-S, respectively. The ux-limit dependence translates into a luminosity dependent X-ray AGN clustering. Applying the standard formalism relating the theoretical CDM model clustering to the data in a at cosmology (for w =-1 and h = 0:72, we nd: m ' 0:28 0:03 and 8 ' 0:75 0:03; while utilizing also the SN Ia Hubble relation (for 8 = 0:75 and h = 0:72, we nd: m ' 0:26 0:04 and w = 0:9 0:1

  13. XMM-Newton and Chandra Cross Calibration Using HIFLUGCS Galaxy Clusters

    CERN Document Server

    Schellenberger, G; Lovisari, L; Nevalainen, J; David, L

    2014-01-01

    Cosmological constraints from clusters rely on accurate gravitational mass estimates, which strongly depend on cluster gas temperature measurements. Therefore, systematic calibration differences may result in biased, instrument-dependent cosmological constraints. This is of special interest in the light of the tension between the Planck results of the primary temperature anisotropies of the CMB and Sunyaev-Zel'dovich plus X-ray cluster counts analyses. We quantify in detail the systematics and uncertainties of the cross-calibration of the effective area between five X-ray instruments, EPIC-MOS1/MOS2/PN onboard XMM-Newton and ACIS-I/S onboard Chandra, and the influence on temperature measurements. Furthermore, we assess the impact of the cross calibration uncertainties on cosmology. Using the HIFLUGCS sample, consisting of the 64 X-ray brightest galaxy clusters, we constrain the ICM temperatures through spectral fitting in the same, mostly isothermal, regions and compare them. Our work is an extension to a pre...

  14. Chandra Finds Most Distant X-ray Galaxy Cluster

    Science.gov (United States)

    2001-02-01

    The most distant X-ray cluster of galaxies yet has been found by astronomers using NASA’s Chandra X-ray Observatory. Approximately 10 billion light years from Earth, the cluster 3C294 is 40 percent farther than the next most distant X-ray galaxy cluster. The existence of such a distant galaxy cluster is important for understanding how the universe evolved. "Distant objects like 3C294 provide snapshots to how these galaxy clusters looked billions of years ago," said Andrew Fabian of the Institute of Astronomy, Cambridge, England and lead author of the paper accepted for publication in the Monthly Notices of Britain’s Royal Astronomical Society. "These latest results help us better understand what the universe was like when it was only 20 percent of its current age." Chandra’s image reveals an hourglass-shaped region of X-ray emission centered on the previously known central radio source. This X-ray emission extends outward from the central galaxy for at least 300,000 light years and shows that the known radio source is in the central galaxy of a massive cluster. Scientists have long suspected that distant radio-emitting galaxies like 3C294 are part of larger groups of galaxies known as "clusters." However, radio data provides astronomers with only a partial picture of these distant objects. Confirmation of the existence of clusters at great distances - and, hence, at early stages of the universe - requires information from other wavelengths. Optical observations can be used to pinpoint individual galaxies, but X-ray data are needed to detect the hot gas that fills the space within the cluster. "Galaxy clusters are the largest gravitationally bound structures in the universe," said Fabian. "We do not expect to find many massive objects, such as the 3C294 cluster, in early times because structure is thought to grow from small scales to large scales." The vast clouds of hot gas that envelope galaxies in clusters are thought to be heated by collapse toward the

  15. Cosmology and cluster halo scaling relations

    NARCIS (Netherlands)

    Araya-Melo, Pablo A.; van de Weygaert, Rien; Jones, Bernard J. T.

    2009-01-01

    We explore the effects of dark matter and dark energy on the dynamical scaling properties of galaxy clusters. We investigate the cluster Faber-Jackson (FJ), Kormendy and Fundamental Plane (FP) relations between the mass, radius and velocity dispersion of cluster-sized haloes in cosmological N-body s

  16. Statistical issues in galaxy cluster cosmology

    DEFF Research Database (Denmark)

    Mantz, Adam; Allen, Steven W.; Rapetti Serra, David Angelo

    2013-01-01

    The number and growth of massive galaxy clusters is a sensitive probe of cosmological structure formation and dark energy. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneo......The number and growth of massive galaxy clusters is a sensitive probe of cosmological structure formation and dark energy. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us...... to simultaneously constrain scaling relations of observable signals with mass. The problem can be cast in the form of a regression, in which the data set is truncated, the (cosmology-dependent) underlying population must be modeled, and strong, complex correlations between measurements often exist. © Springer...... Science+Business Media New York 2013....

  17. Chandra Finds Surprising Black Hole Activity In Galaxy Cluster

    Science.gov (United States)

    2002-09-01

    Scientists at the Carnegie Observatories in Pasadena, California, have uncovered six times the expected number of active, supermassive black holes in a single viewing of a cluster of galaxies, a finding that has profound implications for theories as to how old galaxies fuel the growth of their central black holes. The finding suggests that voracious, central black holes might be as common in old, red galaxies as they are in younger, blue galaxies, a surprise to many astronomers. The team made this discovery with NASA'S Chandra X-ray Observatory. They also used Carnegie's 6.5-meter Walter Baade Telescope at the Las Campanas Observatory in Chile for follow-up optical observations. "This changes our view of galaxy clusters as the retirement homes for old and quiet black holes," said Dr. Paul Martini, lead author on a paper describing the results that appears in the September 10 issue of The Astrophysical Journal Letters. "The question now is, how do these black holes produce bright X-ray sources, similar to what we see from much younger galaxies?" Typical of the black hole phenomenon, the cores of these active galaxies are luminous in X-ray radiation. Yet, they are obscured, and thus essentially undetectable in the radio, infrared and optical wavebands. "X rays can penetrate obscuring gas and dust as easily as they penetrate the soft tissue of the human body to look for broken bones," said co-author Dr. Dan Kelson. "So, with Chandra, we can peer through the dust and we have found that even ancient galaxies with 10-billion-year-old stars can have central black holes still actively pulling in copious amounts of interstellar gas. This activity has simply been hidden from us all this time. This means these galaxies aren't over the hill after all and our theories need to be revised." Scientists say that supermassive black holes -- having the mass of millions to billions of suns squeezed into a region about the size of our Solar System -- are the engines in the cores of

  18. New Cosmology with Clusters of Galaxies

    CERN Document Server

    Schücker, P

    2005-01-01

    The review summarizes present and future applications of galaxy clusters to cosmology with emphasis on nearby X-ray clusters. The discussion includes the density of dark matter, the normalization of the matter power spectrum, neutrino masses, and especially the equation of state of the dark energy, the interaction between dark energy and ordinary matter, gravitational holography, and the effects of extra-dimensions.

  19. Testing cosmology with galaxy clusters

    DEFF Research Database (Denmark)

    Rapetti Serra, David Angelo

    2011-01-01

    PASCOS 2011 will be held in Cambridge UK. The conference will be hosted by the Centre for Theoretical Cosmology (DAMTP) at the Mathematical Sciences site in the University of Cambridge. The aim of the conference is to explore and develop synergies between particle physics, string theory and cosmo......PASCOS 2011 will be held in Cambridge UK. The conference will be hosted by the Centre for Theoretical Cosmology (DAMTP) at the Mathematical Sciences site in the University of Cambridge. The aim of the conference is to explore and develop synergies between particle physics, string theory...... and cosmology. There will be an emphasis on timely interdisciplinary topics: • critical tests of inflationary cosmology • advances in fundamental cosmology • applications of string theory (AdS/CMT) • particle and string phenomenology • new experimental particle physics results • and cosmological probes......, Princeton) Nima Arkani-Hamed (IAS, Princeton) Alan Barr (University of Oxford) Cliff Burgess (Perimeter/McMaster University) Paolo Creminelli (ICTP, Trieste) George Efstathiou (Kavli/IoA, Cambridge) Val Gibson (Cavendish, Cambridge) Sean Hartnoll (Stanford University) Shamit Kachru (Stanford University...

  20. Searching for bulk motions in the ICM of massive, merging clusters with Chandra CCD data

    CERN Document Server

    Liu, Ang; Tozzi, Paolo; Zhu, Zong-Hong

    2016-01-01

    We search for bulk motions in the Intra Cluster Medium (ICM) of massive clusters showing evidence of an ongoing or a recent major merger, with spatially resolved spectroscopy in {\\sl Chandra} CCD data. We identify a sample of 6 merging clusters with >150 ks {\\sl Chandra} exposure in the redshift range 0.1 1000$ km/s in the ICM of massive merging clusters at 0.1 < z < 0.3. Despite the CCD spectral resolution is not sufficient for a detailed analysis of the ICM dynamics, {\\sl Chandra} CCD data constitute a key diagnostic tool complementary to X-ray bolometers onboard future X-ray missions.

  1. Statistical Issues in Galaxy Cluster Cosmology

    Science.gov (United States)

    Mantz, Adam

    2013-01-01

    The number and growth of massive galaxy clusters are sensitive probes of cosmological structure formation. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneously constrain scaling relations of observable signals with mass. The problem can be cast as one of regression, in which the data set is truncated, the (cosmology-dependent) underlying population must be modeled, and strong, complex correlations between measurements often exist. Simulations of cosmological structure formation provide a robust prediction for the number of clusters in the Universe as a function of mass and redshift (the mass function), but they cannot reliably predict the observables used to detect clusters in sky surveys (e.g. X-ray luminosity). Consequently, observers must constrain observable-mass scaling relations using additional data, and use the scaling relation model in conjunction with the mass function to predict the number of clusters as a function of redshift and luminosity.

  2. Chandra Observations of Dying Radio Sources in Galaxy Clusters

    Science.gov (United States)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-01-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims. We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods. We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results. The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions. We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  3. LOFAR, VLA, and Chandra observations of the Toothbrush galaxy cluster

    CERN Document Server

    van Weeren, R J; Brüggen, M; Andrade-Santos, F; Ogrean, G A; Williams, W L; Röttgering, H J A; Dawson, W A; Forman, W R; de Gasperin, F; Hardcastle, M J; Jones, C; Miley, G K; Rafferty, D A; Rudnick, L; Sabater, J; Sarazin, C L; Shimwell, T W; Bonafede, A; Best, P N; Bîrzan, L; Cassano, R; Chyży, K T; Croston, J H; Dijkema, T J; Ensslin, T; Ferrari, C; Heald, G; Hoeft, M; Horellou, C; Jarvis, M J; Kraft, R P; Mevius, M; Intema, H T; Murray, S S; Orrú, E; Pizzo, R; Sridhar, S S; Simionescu, A; Stroe, A; van der Tol, S; White, G J

    2016-01-01

    We present deep LOFAR observations between 120-181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of $\\alpha = -0.8 \\pm 0.1$ at the northern edge of the main radio relic, steepening towards the south to $\\alpha \\approx - 2$. The spectral index of the radio halo is remarkably uniform ($\\alpha = -1.16$, with an intrinsic scatter of $\\leq 0.04$). The observed radio relic spectral index gives a Mach number of $\\mathcal{M} = 2.8^{+0.5}_{-0.3}$, assuming diffusive shock acceleration (DSA). However, the gas density jump at the northern edge of the large radio r...

  4. AEGIS: Chandra Observation of DEEP2 Galaxy Groups and Clusters

    CERN Document Server

    Fang, T; Davis, D; Newman, J; Davis, M; Nandra, K; Laird, E; Koo, D; Coil, A; Cooper, M; Croton, D; Yan, R

    2006-01-01

    We present a 200 ksec Chandra observation of seven spectroscopically selected, high redshift (0.75 < z < 1.03) galaxy groups and clusters discovered by the DEEP2 Galaxy Redshift Survey in the Extended Groth Strip (EGS). X-ray emission at the locations of these systems is consistent with background. The 3-sigma upper limits on the bolometric X-ray luminosities (L_X) of these systems put a strong constraint on the relation between L_X and the velocity dispersion of member galaxies sigma_gal at z~1; the DEEP2 systems have lower luminosity than would be predicted by the local relation. Our result is consistent with recent findings that at high redshift, optically selected clusters tend to be X-ray underluminous. A comparison with mock catalogs indicates that it is unlikely that this effect is entirely caused by a measurement bias between sigma_gal and the dark matter velocity dispersion. Physically, the DEEP2 systems may still be in the process of forming and hence not fully virialized, or they may be defic...

  5. Cosmological Parameters from Observations of Galaxy Clusters

    CERN Document Server

    Allen, Steven W; Mantz, Adam B

    2011-01-01

    Studies of galaxy clusters have proved crucial in helping to establish the standard model of cosmology, with a universe dominated by dark matter and dark energy. A theoretical basis for understanding clusters as massive, multi-component, quasi-equilibrium systems has been developed, and is growing in its capability to interpret multi-wavelength observations of expanding scope and sensitivity. We review current cosmological results, including contributions to fundamental physics, obtained from observations of galaxy clusters. These results are consistent with and complementary to those from other methods. We highlight several areas of opportunity for the next few years, and emphasize the need for accurate modeling of survey selection and sources of systematic error. Capitalizing on these opportunities will require a multi-wavelength approach and the application of rigorous statistical frameworks, utilizing the combined strengths of observers, simulators and theorists.

  6. Cosmological Constraints with Clustering-Based Redshifts

    CERN Document Server

    Kovetz, Ely D; Rahman, Mubdi

    2016-01-01

    We demonstrate that observations lacking reliable redshift information, such as photometric and radio continuum surveys, can produce robust measurements of cosmological parameters when empowered by clustering-based redshift estimation. This method infers the redshift distribution based on the spatial clustering of sources, using cross-correlation with a reference dataset with known redshifts. Applying this method to the existing SDSS photometric galaxies, and projecting to future radio continuum surveys, we show that sources can be efficiently divided into several redshift bins, increasing their ability to constrain cosmological parameters. We forecast constraints on the dark-energy equation-of-state and on local non-gaussianity parameters. We explore several pertinent issues, including the tradeoff between including more sources versus minimizing the overlap between bins, the shot-noise limitations on binning, and the predicted performance of the method at high redshifts. Remarkably, we find that, once this ...

  7. Cool Core Clusters from Cosmological Simulations

    CERN Document Server

    Rasia, E; Murante, G; Planelles, S; Beck, A M; Biffi, V; Ragone-Figueroa, C; Granato, G L; Steinborn, L K; Dolag, K

    2015-01-01

    We present results obtained from a set of cosmological hydrodynamic simulations of galaxy clusters, aimed at comparing predictions with observational data on the diversity between cool-core and non-cool-core clusters. Our simulations include the effects of stellar and AGN feedback and are based on an improved version of the Smoothed-Particle-Hydrodynamics code GADGET-3, which ameliorates gas mixing and better captures gas-dynamical instabilities by including a suitable artificial thermal diffusion. In this Letter, we focus our analysis on the entropy profiles, our primary diagnostic to classify the degree of cool-coreness of clusters, and on the iron profiles. In keeping with observations, our simulated clusters display a variety of behaviors in entropy profiles: they range from steadily decreasing profiles at small radii, characteristic of cool-core systems, to nearly flat core isentropic profiles, characteristic of non cool-core systems. Using observational criteria to distinguish between the two classes of...

  8. Chandra Observations of the Components of Clusters, Groups, and Galaxies and their Interactions

    CERN Document Server

    Forman, W; Markevitch, M L; Vikhlinin, A A; Churazov, E

    2001-01-01

    We discuss two themes from Chandra observations of galaxies, groups, and clusters. First, we review the merging process as seen through the high angular resolution of Chandra. We present examples of sharp, edge-like surface brightness structures ``cold fronts'', the boundaries of the remaining cores of merger components and the Chandra observations of CL0657, the first clear example of a strong cluster merger shock. In addition to reviewing already published work, we present observations of the cold front around the elliptical galaxy NGC1404 which is infalling into the Fornax cluster and we discuss multiple ``edges'' in ZW3146. Second, we review the effects of relativistic, radio-emitting plasmas or ``bubbles'', inflated by active galactic nuclei, on the hot X-ray emitting gaseous atmospheres in galaxies and clusters. We review published work and also discuss the unusual X-ray structures surrounding the galaxies NGC4636 and NGC507.

  9. Testing X-ray Measurements of Galaxy Cluster Outskirts with Cosmological Simulations

    CERN Document Server

    Avestruz, Camille; Nagai, Daisuke; Vikhlinin, Alexey

    2014-01-01

    The study of galaxy cluster outskirts has emerged as one of the new frontiers in extragalactic astrophysics and cosmology with the advent of new observations in X-ray and microwave. However, the thermodynamic properties and chemical enrichment of this diffuse and azimuthally asymmetric component of the intra-cluster medium are still not well understood. This work, for the first time, systematically explores potential observational biases in these regions. To assess X-ray measurements of galaxy cluster properties at large radii ($>{R}_{500c}$), we use mock Chandra analyses of cosmological galaxy cluster simulations. The pipeline is identical to that used for Chandra observations, but the biases discussed in this paper are relevant for all X-ray observations outside of ${R}_{500c}$. We find the following from our analysis: (1) filament regions can contribute as much as a factor of 3 to the emission measure, (2) X-ray temperatures and metal abundances from model fitted mock X-ray spectra respectively vary to the...

  10. COOL CORE CLUSTERS FROM COSMOLOGICAL SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Rasia, E.; Borgani, S.; Murante, G.; Planelles, S.; Biffi, V.; Granato, G. L. [INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34131, Trieste (Italy); Beck, A. M.; Steinborn, L. K.; Dolag, K. [Universitäts-Sternwarte München, Scheinerstr.1, D-81679 München (Germany); Ragone-Figueroa, C., E-mail: rasia@oats.inaf.it [Instituto de Astronomá Teórica y Experimental (IATE), Consejo Nacional de Investigaciones Cientiíficas y Técnicas de la República Argentina (CONICET), Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, X5000BGR, Córdoba (Argentina)

    2015-11-01

    We present results obtained from a set of cosmological hydrodynamic simulations of galaxy clusters, aimed at comparing predictions with observational data on the diversity between cool-core (CC) and non-cool-core (NCC) clusters. Our simulations include the effects of stellar and active galactic nucleus (AGN) feedback and are based on an improved version of the smoothed particle hydrodynamics code GADGET-3, which ameliorates gas mixing and better captures gas-dynamical instabilities by including a suitable artificial thermal diffusion. In this Letter, we focus our analysis on the entropy profiles, the primary diagnostic we used to classify the degree of cool-coreness of clusters, and the iron profiles. In keeping with observations, our simulated clusters display a variety of behaviors in entropy profiles: they range from steadily decreasing profiles at small radii, characteristic of CC systems, to nearly flat core isentropic profiles, characteristic of NCC systems. Using observational criteria to distinguish between the two classes of objects, we find that they occur in similar proportions in both simulations and observations. Furthermore, we also find that simulated CC clusters have profiles of iron abundance that are steeper than those of NCC clusters, which is also in agreement with observational results. We show that the capability of our simulations to generate a realistic CC structure in the cluster population is due to AGN feedback and artificial thermal diffusion: their combined action allows us to naturally distribute the energy extracted from super-massive black holes and to compensate for the radiative losses of low-entropy gas with short cooling time residing in the cluster core.

  11. CHANDRA OBSERVATION OF ABELL 1142: A COOL-CORE CLUSTER LACKING A CENTRAL BRIGHTEST CLUSTER GALAXY?

    Energy Technology Data Exchange (ETDEWEB)

    Su, Yuanyuan; Weeren, Reinout van [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Buote, David A. [Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Gastaldello, Fabio, E-mail: yuanyuan.su@cfa.harvard.edu [INAF-IASF-Milano, Via E. Bassini 15, I-20133 Milano (Italy)

    2016-04-10

    Abell 1142 is a low-mass galaxy cluster at low redshift containing two comparable brightest cluster galaxies (BCGs) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal-rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool-core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters, each of which contain one BCG. The BCGs are merging at a relative velocity of ≈1200 km s{sup −1}. This ongoing merger may have shock-heated the ICM from ≈2 keV to above 3 keV, which would explain the anomalous L{sub X}–T{sub X} scaling relation for this system. This merger may have displaced the metal-enriched “cool core” of either of the subclusters from the BCG. The southern BCG consists of three individual galaxies residing within a radius of 5 kpc in projection. These galaxies should rapidly sink into the subcluster center due to the dynamical friction of a cuspy cold dark matter halo.

  12. Chandra Observation of Abell 1142: A Cool-Core Cluster Lacking a Central Brightest Cluster Galaxy?

    CERN Document Server

    Su, Yuanyuan; Gastaldello, Fabio; van Weeren, Reinout

    2016-01-01

    Abell~1142 is a low-mass galaxy cluster at low redshift containing two comparable Brightest Cluster Galaxies (BCG) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters with each containing one BCG. The BCGs are merging at a relative velocity of ~1200 km/s. This ongoing merger may have shock-heated the ICM from ~ 2 keV to above 3 keV, which would explain the anomalous L_X--T_X scaling relation for this system. This merger may have displaced the metal-enriched "cool core" of eith...

  13. High-Resolution Chandra X-ray Imaging and Spectroscopy of the Sigma Orionis Cluster

    OpenAIRE

    Skinner, S.L.; Sokal, K. R.; Cohen, D. H.; Gagne, M.; Owocki, S.P.; Townsend, R. D.

    2008-01-01

    We present results of a 90 ksec Chandra X-ray observation of the young sigma Orionis cluster (age ~3 Myr) obtained with the High Energy Transmission Grating Spectrometer. We use the high resolution grating spectrum and moderate resolution CCD spectrum of the massive central star sigma Ori AB (O9.5V + B0.5V) to test wind shock theories of X-ray emission and also analyze the high spatial resolution zero-order ACIS-S image of the central cluster region. Chandra detected 42 X-ray sources on the p...

  14. Influence of Projection in Cluster Cosmology Studies

    CERN Document Server

    Erickson, Brandon M S; Evrard, August E

    2011-01-01

    Projection tends to skew the mass-observable relation of galaxy clusters by creating a small fraction of severely blended systems, those for which the measured observable property of a cluster is strongly boosted relative to the value of its primary host halo. We examine the bias in cosmological parameter estimates caused by incorrectly assuming a Gaussian (projection-free) mass-observable relation when the true relation is non-Gaussian due to projection. We introduce a mixture model for projection and explore Fisher forecasts for a survey of 5000 sq. deg. to z=1.1 and an equivalent mass threshold of 10^13.7 h^-1 solar masses. Using a blended fraction motivated by optical cluster finding applied to the Millennium Simulation and applying Planck and otherwise weak priors, we find that the biases in Omega_DE and w are significant, being factors of 2.8 and 2.4, respectively, times previous forecast uncertainties. Incorporating eight new degrees of freedom to describe cluster selection with projection increases th...

  15. Cosmological Constraints from Galaxy Clusters in the 2500 square-degree SPT-SZ Survey

    CERN Document Server

    de Haan, T; Bleem, L E; Allen, S W; Applegate, D E; Ashby, M L N; Bautz, M; Bayliss, M; Bocquet, S; Brodwin, M; Carlstrom, J E; Chang, C L; Chiu, I; Cho, H-M; Clocchiatti, A; Crawford, T M; Crites, A T; Desai, S; Dietrich, J P; Dobbs, M A; Doucouliagos, A N; Foley, R J; Forman, W R; Garmire, G P; George, E M; Gladders, M D; Gonzalez, A H; Gupta, N; Halverson, N W; Hlavacek-Larrondo, J; Hoekstra, H; Holder, G P; Holzapfel, W L; Hou, Z; Hrubes, J D; Huang, N; Jones, C; Keisler, R; Knox, L; Lee, A T; Leitch, E M; von der Linden, A; Luong-Van, D; Mantz, A; Marrone, D P; McDonald, M; McMahon, J J; Meyer, S S; Mocanu, L M; Mohr, J J; Murray, S S; Padin, S; Pryke, C; Rapetti, D; Reichardt, C L; Rest, A; Ruel, J; Ruhl, J E; Saliwanchik, B R; Saro, A; Sayre, J T; Schaffer, K K; Schrabback, T; Shirokoff, E; Song, J; Spieler, H G; Stalder, B; Stanford, S A; Staniszewski, Z; Stark, A A; Story, K T; Stubbs, C W; Vanderlinde, K; Vieira, J D; Vikhlinin, A; Williamson, R; Zenteno, A

    2016-01-01

    (abridged) We present cosmological constraints obtained from galaxy clusters identified by their Sunyaev-Zel'dovich effect signature in the 2500 square degree South Pole Telescope Sunyaev Zel'dovich survey. We consider the 377 cluster candidates identified at z>0.25 with a detection significance greater than five, corresponding to the 95% purity threshold for the survey. We compute constraints on cosmological models using the measured cluster abundance as a function of mass and redshift. We include additional constraints from multi-wavelength observations, including Chandra X-ray data for 82 clusters and a weak lensing-based prior on the normalization of the mass-observable scaling relations. Assuming a LCDM cosmology, where the species-summed neutrino mass has the minimum allowed value (mnu = 0.06 eV) from neutrino oscillation experiments, we combine the cluster data with a prior on H0 and find sigma_8 = 0.797+-0.031 and Omega_m = 0.289+-0.042, with the parameter combination sigma_8(Omega_m/0.27)^0.3 = 0.784...

  16. Resolving galaxy cluster gas properties at z~1 with XMM-Newton and Chandra

    CERN Document Server

    Bartalucci, I; Pratt, G W; Démoclès, J; van der Burg, R F J; Mazzotta, P

    2016-01-01

    We present a pilot X-ray study of the five most massive ($M_{500}>5 \\times 10^{14} M_{\\odot}$), distant (z~1), galaxy clusters detected via the Sunyaev-Zeldovich effect. We optimally combine XMM-Newton and Chandra X-ray observations by leveraging the throughput of XMM to obtain spatially-resolved spectroscopy, and the spatial resolution of Chandra to probe the bright inner parts and to detect embedded point sources. Capitalising on the excellent agreement in flux-related measurements, we present a new method to derive the density profiles, constrained in the centre by Chandra and in the outskirts by XMM. We show that the Chandra-XMM combination is fundamental for morphological analysis at these redshifts, the Chandra resolution being required to remove point source contamination, and the XMM sensitivity allowing higher significance detection of faint substructures. The sample is dominated by dynamically disturbed objects. We use the combined Chandra-XMM density profiles and spatially-resolved temperature prof...

  17. The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected Via the Sunyaev-Zel'dovich Effect

    Science.gov (United States)

    Sehgal, Neelima; Trac, Hy; Acquaviva, Viviana; Ade, Peter A. R.; Aguirre, Paula; Amiri, Mandana; Appel, John W.; Barrientos, L. Felipe; Battistelli, Elia S.; Bond, J. Richard; Brown, Ben; Burger, Bryce; Chervenak, Jay; Das, Sudeep; Devlin, Mark J.; Dicker, Simon R.; Doriese, W. Bertrand; Dunkley, Joanna; Duenner, Rolando; Essinger-Hileman, Thomas; Fisher, Ryan P.; Fowler, Joseph W.; Hajian, Amir; Halpern, Mark; Wollack, Ed

    2010-01-01

    We present constraints on cosmological parameters based on a sample of Sunyaev-Zel'dovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148 GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives (sigma)8 = 0.851 +/- 0.115 and w = -1.14 +/- 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find (sigma)8 + 0.821 +/- 0.044 and w = -1.05 +/- 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernova which give (sigma)8 = 0.802 +/- 0.038 and w = -0.98 +/- 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.

  18. Cosmological Constraints from Galaxy Clusters in the 2500 square-degree SPT-SZ Survey

    Energy Technology Data Exchange (ETDEWEB)

    de Haan, T.; et al.

    2016-03-21

    (abridged) We present cosmological constraints obtained from galaxy clusters identified by their Sunyaev-Zel'dovich effect signature in the 2500 square degree South Pole Telescope Sunyaev Zel'dovich survey. We consider the 377 cluster candidates identified at z>0.25 with a detection significance greater than five, corresponding to the 95% purity threshold for the survey. We compute constraints on cosmological models using the measured cluster abundance as a function of mass and redshift. We include additional constraints from multi-wavelength observations, including Chandra X-ray data for 82 clusters and a weak lensing-based prior on the normalization of the mass-observable scaling relations. Assuming a LCDM cosmology, where the species-summed neutrino mass has the minimum allowed value (mnu = 0.06 eV) from neutrino oscillation experiments, we combine the cluster data with a prior on H0 and find sigma_8 = 0.797+-0.031 and Omega_m = 0.289+-0.042, with the parameter combination sigma_8(Omega_m/0.27)^0.3 = 0.784+-0.039. These results are in good agreement with constraints from the CMB from SPT, WMAP, and Planck, as well as with constraints from other cluster datasets. Adding mnu as a free parameter, we find mnu = 0.14+-0.08 eV when combining the SPT cluster data with Planck CMB data and BAO data, consistent with the minimum allowed value. Finally, we consider a cosmology where mnu and N_eff are fixed to the LCDM values, but the dark energy equation of state parameter w is free. Using the SPT cluster data in combination with an H0 prior, we measure w = -1.28+-0.31, a constraint consistent with the LCDM cosmological model and derived from the combination of growth of structure and geometry. When combined with primarily geometrical constraints from Planck CMB, H0, BAO and SNe, adding the SPT cluster data improves the w constraint from the geometrical data alone by 14%, to w = -1.023+-0.042.

  19. The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected via the Sunyaev-Zel'dovich Effect

    CERN Document Server

    Sehgal, Neelima; Acquaviva, Viviana; Ade, Peter A R; Aguirre, Paula; Amiri, Mandana; Appel, John W; Barrientos, L Felipe; Battistelli, Elia S; Bond, J Richard; Brown, Ben; Burger, Bryce; Chervenak, Jay; Das, Sudeep; Devlin, Mark J; Dicker, Simon R; Doriese, W Bertrand; Dunkley, Joanna; Dünner, Rolando; Essinger-Hileman, Thomas; Fisher, Ryan P; Fowler, Joseph W; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hernández-Monteagudo, Carlos; Hilton, Gene C; Hilton, Matt; Hincks, Adam D; Hlozek, Renée; Holtz, David; Huffenberger, Kevin M; Hughes, David H; Hughes, John P; Infante, Leopoldo; Irwin, Kent D; Jones, Andrew; Juin, Jean Baptiste; Klein, Jeff; Kosowsky, Arthur; Lau, Judy M; Limon, Michele; Lin, Yen-Ting; Lupton, Robert H; Marriage, Tobias A; Marsden, Danica; Martocci, Krista; Mauskopf, Phil; Menanteau, Felipe; Moodley, Kavilan; Moseley, Harvey; Netterfield, Calvin B; Niemack, Michael D; Nolta, Michael R; Page, Lyman A; Parker, Lucas; Partridge, Bruce; Reid, Beth; Sherwin, Blake D; Sievers, Jon; Spergel, David N; Staggs, Suzanne T; Swetz, Daniel S; Switzer, Eric R; Thornton, Robert; Tucker, Carole; Warne, Ryan; Wollack, Ed; Zhao, Yue

    2010-01-01

    We present constraints on cosmological parameters based on a sample of Sunyaev-Zel'dovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148 GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives sigma_8 = 0.851 +/- 0.115 and w = -1.14 +/- 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluste...

  20. Precision Cosmology with Clusters of Galaxies: Insights from Numerical Simulations

    Science.gov (United States)

    Motl, P. M.; Burns, J. O.; Norman, M. L.

    2004-08-01

    Clusters of galaxies have emerged as powerful and complementary probes in contemporary cosmology. However, the simplifying assumptions used to interpret cluster observations (spherical symmetry, isothermality, hydrostatic equilibrium, etc.) are approximations that are valid to only a certain level. Especially in the new era of precision cosmology, where efforts are underway to investigate the nature and evolution of dark energy, it is crucial to calibrate the approximations used to reduce observations of the Sunyaev-Zeldovich effect or X-ray emission in clusters of galaxies. We use high-resolution, cosmological, adaptive mesh refinement simulations to quantify the limiting accuracy and potential bias imposed by common assumptions for observables such as the gravitating mass of clusters and the Hubble constant.

  1. A Chandra Study of Temperature Distributions of the Intracluster Medium in 50 Galaxy Clusters

    Science.gov (United States)

    Zhu, Zhenghao; Xu, Haiguang; Wang, Jingying; Gu, Junhua; Li, Weitian; Hu, Dan; Zhang, Chenhao; Gu, Liyi; An, Tao; Liu, Chengze; Zhang, Zhongli; Zhu, Jie; Wu, Xiang-Ping

    2016-01-01

    To investigate the spatial distribution of the intracluster medium temperature in galaxy clusters in a quantitative way and probe the physics behind it, we analyze the X-ray spectra from a sample of 50 clusters that were observed with the Chandra ACIS instrument over the past 15 years and measure the radial temperature profiles out to 0.45r500. We construct a physical model that takes into consideration the effects of gravitational heating, thermal history (such as radiative cooling, active galactic nucleus feedback, and thermal conduction), and work done via gas compression, and use it to fit the observed temperature profiles by running Bayesian regressions. The results show that in all cases our model provides an acceptable fit at the 68% confidence level. For further validation, we select nine clusters that have been observed with both Chandra (out to ≳0.3r500) and Suzaku (out to ≳1.5r500) and fit their Chandra spectra with our model. We then compare the extrapolation of the best fits with the Suzaku measurements and find that the model profiles agree with the Suzaku results very well in seven clusters. In the remaining two clusters the difference between the model and the observation is possibly caused by local thermal substructures. Our study also implies that for most of the clusters the assumption of hydrostatic equilibrium is safe out to at least 0.5r500 and the non-gravitational interactions between dark matter and its luminous counterparts is consistent with zero.

  2. Cosmological Constraints from the SDSS maxBCG Cluster Catalog

    Energy Technology Data Exchange (ETDEWEB)

    Rozo, Eduardo; /CCAPP; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Rykoff, Eli S.; /UC, Santa Barbara; Annis, James T.; /Fermilab; Becker, Matthew R.; /Chicago U. /KICP, Chicago; Evrard, August E.; /Michigan U. /Michigan U., MCTP; Frieman, Joshua A.; /Fermilab /KICP, Chicago /Chicago U.; Hansen, Sarah M.; /UC, Santa Cruz; Hao, Jia; /Michigan U.; Johnston, David E.; /Northwestern U.; Koester, Benjamin P.; /KICP, Chicago /Chicago U.; McKay, Timothy A.; /Michigan U. /Michigan U., MCTP; Sheldon, Erin S.; /Brookhaven; Weinberg, David H.; /CCAPP /Ohio State U.

    2009-08-03

    We use the abundance and weak lensing mass measurements of the SDSS maxBCG cluster catalog to simultaneously constrain cosmology and the richness-mass relation of the clusters. Assuming a flat {Lambda}CDM cosmology, we find {sigma}{sub 8}({Omega}{sub m}/0.25){sup 0.41} = 0.832 {+-} 0.033 after marginalization over all systematics. In common with previous studies, our error budget is dominated by systematic uncertainties, the primary two being the absolute mass scale of the weak lensing masses of the maxBCG clusters, and uncertainty in the scatter of the richness-mass relation. Our constraints are fully consistent with the WMAP five-year data, and in a joint analysis we find {sigma}{sub 8} = 0.807 {+-} 0.020 and {Omega}{sub m} = 0.265 {+-} 0.016, an improvement of nearly a factor of two relative to WMAP5 alone. Our results are also in excellent agreement with and comparable in precision to the latest cosmological constraints from X-ray cluster abundances. The remarkable consistency among these results demonstrates that cluster abundance constraints are not only tight but also robust, and highlight the power of optically-selected cluster samples to produce precision constraints on cosmological parameters.

  3. Chandra view of the dynamically young cluster of galaxies A1367 II. point sources

    CERN Document Server

    Sun, M

    2002-01-01

    A 40 ks \\emph{Chandra} ACIS-S observation of the dynamically young cluster A1367 yields new insights on X-ray emission from cluster member galaxies. We detect 59 point-like sources in the ACIS field, of which 8 are identified with known cluster member galaxies. Thus in total 10 member galaxies are detected in X-rays when three galaxies discussed in paper I (Sun & Murray 2002; NGC 3860 is discussed in both papers) are included. The superior spatial resolution and good spectroscopy capability of \\chandra allow us to constrain the emission nature of these galaxies. Central nuclei, thermal halos and stellar components are revealed in their spectra. Four new low luminosity nuclei (LLAGN) are found, including an absorbed one (NGC 3861). This discovery makes the LLAGN/AGN content in this part of A1367 very high ($\\sim$ 20%). Thermal halos with temperatures around 0.5 - 0.8 keV are revealed in the spectra of two elliptical galaxies NGC 3842 and NGC 3837, which suggests that galactic coronae can survive in cluster...

  4. The outer regions of galaxy clusters: Chandra constraints on the X-ray surface brightness

    CERN Document Server

    Ettori, S

    2008-01-01

    (Abridged version) We study the properties of the X-ray surface brightness profiles in a sample of galaxy clusters that are observed with Chandra and have emission detectable with a signal-to-noise ratio larger than 2 at a radius beyond R500 ~ 0.7 R200. Our study aims at measuring the slopes of the X-ray surface brightness and of the gas density profiles in the outskirts of massive clusters. These constraints are then compared to similar results obtained from observations and numerical simulations of the temperature and dark matter density profiles with the intention to present a consistent picture of the outer regions of galaxy clusters. We extract the surface brightness profiles S_b(r) from X-ray exposures obtained with Chandra of 52 X-ray luminous galaxy clusters at z>0.3. We estimate R200 both using a beta-model to reproduce the surface brightness profile and scaling relations from the literature, showing that the two methods converge to comparable values. We evaluate then the radius, R_S2N, at which the ...

  5. Effects of Cosmological Constant on Clustering of Galaxies

    Science.gov (United States)

    Hameeda, Mir; Upadhyay, Sudhaker; Faizal, Mir; Ali, Ahmed Farag

    2016-09-01

    In this paper, we analyse the effect of the expansion of the universe on the clustering of galaxies. We evaluate the configurational integral for interacting system of galaxies in an expanding universe by including effects produced by the cosmological constant. The gravitational partition function is obtained using this configuration integral. Thermodynamic quantities, specifically, Helmholtz free energy, entropy, internal energy, pressure and chemical potential are also derived for this system. It is observed that they depend on the modified clustering parameter for this system of galaxies. It is also demonstrated that these thermodynamical quantities get corrected because of the cosmological constant.

  6. Effects of Cosmological Constant on Clustering of Galaxies

    CERN Document Server

    Hameeda, Mir; Faizal, Mir; Ali, Ahmed Farag

    2016-01-01

    In this paper, we analyse the effect of the expansion of the universe on the clustering of galaxies. We evaluate the configurational integral for interacting system of galaxies in an expanding universe by including effects produced by the cosmological constant. The gravitational partition function is obtained using this configuration integral. Thermodynamic quantities, specifically, Helmholtz free energy, entropy, internal energy, pressure and chemical potential are also derived for this system. It is observed that they depend on the modified clustering parameter for this system of galaxies. It is also demonstrated that these thermodynamical quantities get corrected because of the cosmological constant.

  7. Cosmological analysis of galaxy clusters surveys in X-rays

    International Nuclear Information System (INIS)

    Clusters of galaxies are the most massive objects in equilibrium in our Universe. Their study allows to test cosmological scenarios of structure formation with precision, bringing constraints complementary to those stemming from the cosmological background radiation, supernovae or galaxies. They are identified through the X-ray emission of their heated gas, thus facilitating their mapping at different epochs of the Universe. This report presents two surveys of galaxy clusters detected in X-rays and puts forward a method for their cosmological interpretation. Thanks to its multi-wavelength coverage extending over 10 sq. deg. and after one decade of expertise, the XMM-LSS allows a systematic census of clusters in a large volume of the Universe. In the framework of this survey, the first part of this report describes the techniques developed to the purpose of characterizing the detected objects. A particular emphasis is placed on the most distant ones (z ≥ 1) through the complementarity of observations in X-ray, optical and infrared bands. Then the X-CLASS survey is fully described. Based on XMM archival data, it provides a new catalogue of 800 clusters detected in X-rays. A cosmological analysis of this survey is performed thanks to 'CR-HR' diagrams. This new method self-consistently includes selection effects and scaling relations and provides a means to bypass the computation of individual cluster masses. Propositions are made for applying this method to future surveys as XMM-XXL and eRosita. (author)

  8. Limitations on Precision Cosmology using Mass Measurements of Galaxy Clusters

    CERN Document Server

    Hallman, E J; Burns, J O; Norman, M L; Hallman, Eric J.; Motl, Patrick M.; Burns, Jack O.; Norman, Michael L.

    2005-01-01

    We critically analyze the role of clusters of galaxies as probes for precision cosmology. Using synthetic observations of numerically simulated clusters viewed through their X-ray emission and thermal Sunyaev-Zeldovich effect (SZE), we reduce the observations to attain measurements of the cluster gas mass. We utilize both parametric models such as the isothermal cluster model and non-parametric models that involve the geometric deprojection of the cluster emission assuming spherical symmetry. We are thus able to quantify the possible sources of uncertainty and systematic bias associated with the common simplifying assumptions used in reducing real cluster observations including isothermality and hydrostatic equilibrium. We find that intrinsic variations in clusters limit the precision of observational gas mass estimation to ~10% to 80% confidence excluding instrumental effects. For the full cluster sample, methods that use SZE profiles out to roughly the virial radius are the most accurate and precise way to ...

  9. Applications for edge detection techniques using Chandra and XMM-Newton data: galaxy clusters and beyond

    Science.gov (United States)

    Walker, S. A.; Sanders, J. S.; Fabian, A. C.

    2016-09-01

    The unrivalled spatial resolution of the Chandra X-ray observatory has allowed many breakthroughs to be made in high-energy astrophysics. Here we explore applications of Gaussian gradient magnitude (GGM) filtering to X-ray data, which dramatically improves the clarity of surface brightness edges in X-ray observations, and maps gradients in X-ray surface brightness over a range of spatial scales. In galaxy clusters, we find that this method is able to reveal remarkable substructure behind the cold fronts in Abell 2142 and Abell 496, possibly the result of Kelvin-Helmholtz instabilities. In Abell 2319 and Abell 3667, we demonstrate that the GGM filter can provide a straightforward way of mapping variations in the widths and jump ratios along the lengths of cold fronts. We present results from our ongoing programme of analysing the Chandra and XMM-Newton archives with the GGM filter. In the Perseus cluster, we identify a previously unseen edge around 850 kpc from the core to the east, lying outside a known large-scale cold front, which is possibly a bow shock. In MKW 3s we find an unusual `V' shape surface brightness enhancement starting at the cluster core, which may be linked to the AGN jet. In the Crab nebula a new, moving feature in the outer part of the torus is identified which moves across the plane of the sky at a speed of ˜0.1c, and lies much further from the central pulsar than the previous motions seen by Chandra.

  10. A Chandra X-ray Study of Cygnus A - III. The Cluster of Galaxies

    OpenAIRE

    Smith, David A.; Wilson, Andrew S.; Arnaud, Keith A.; Terashima, Yuichi; Young, Andrew J.

    2001-01-01

    The results from a recent Chandra ACIS-S study of the cluster surrounding Cygnus A are presented. We have deprojected the X-ray spectra taken from various elliptical shells in order to derive the run of temperature, density, pressure, and abundance for the ICM as a function of radius. We confirm a drop in temperature of the X-ray emitting gas from $\\sim 8$ keV more than $\\sim 2^{\\prime}$ from the center to $\\simeq 5$ keV some $30^{\\prime\\prime}$ from the center, with the coolest gas immediate...

  11. Deep Chandra study of the truncated cool core of the Ophiuchus cluster

    CERN Document Server

    Werner, N; Canning, R E A; Allen, S W; King, A L; Sanders, J S; Simionescu, A; Taylor, G B; Morris, R G; Fabian, A C

    2016-01-01

    We present the results of a deep (280 ks) Chandra observation of the Ophiuchus cluster, the second-brightest galaxy cluster in the X-ray sky. The cluster hosts a truncated cool core, with a temperature increasing from kT~1 keV in the core to kT~9 keV at r~30 kpc. Beyond r~30 kpc the intra-cluster medium (ICM) appears remarkably isothermal. The core is dynamically disturbed with multiple sloshing induced cold fronts, with indications for both Rayleigh-Taylor and Kelvin-Helmholtz instabilities. The sloshing is the result of the strongly perturbed gravitational potential in the cluster core, with the central brightest cluster galaxy (BCG) being displaced southward from the global center of mass. The residual image reveals a likely subcluster south of the core at the projected distance of r~280 kpc. The cluster also harbors a likely radio phoenix, a source revived by adiabatic compression by gas motions in the ICM. Even though the Ophiuchus cluster is strongly dynamically active, the amplitude of density fluctuat...

  12. Clusters of Galaxies as Standard Candles for Global Observational Cosmology

    OpenAIRE

    Roukema, B. F.

    2001-01-01

    As the largest gravitationally collapsed objects, and as objects with a relatively low space density, clusters of galaxies offer one of the best sets of standard candles for trying to measure basic cosmological parameters such as the injectivity diameter 2r_{inj} (the shortest distance between two topologically lensed images of any object, e.g. cluster) and the out-diameter 2r_{+} (the maximum `size' of the Universe). Present constraints indicate that either of these may be smaller or larger ...

  13. Radio relics in a cosmological cluster merger simulation

    OpenAIRE

    Hoeft, Matthias; Brueggen, Marcus; Yepes, Gustavo

    2003-01-01

    Motivated by the discovery of a number of radio relics we investigate the fate of fossil radio plasma during a merger of clusters of galaxies using cosmological smoothed-particle hydrodynamics simulations. Radio relics are extended, steep-spectrum radio sources that do not seem to be associated with a host galaxy. One proposed scenario whereby these relics form is through the compression of fossil radio plasma during a merger between clusters. The ensuing compression of the plasma can lead to...

  14. The cosmological analysis of X-ray cluster surveys; III. Bypassing cluster mass measurements

    CERN Document Server

    Pierre, M; Faccioli, L; Clerc, N; Gastaud, R; Koulouridis, E; Pacaud, F

    2016-01-01

    Despite strong theoretical arguments, the use of clusters as cosmological probes is, in practice, frequently questioned because of the many uncertainties impinging on cluster mass estimates. Our aim is to develop a fully self-consistent cosmological approach of X-ray cluster surveys, exclusively based on observable quantities, rather than masses. This procedure is justified given the possibility to directly derive the cluster properties via ab initio modelling, either analytically or by using hydrodynamical simulations. In this third paper, we evaluate the method on cluster toy-catalogues. We model the population of detected clusters in the count-rate -- hardness-ratio -- angular size -- redshift space and compare the corresponding 4-dimensional diagram with theoretical predictions. The best cosmology+physics parameter configuration is determined using a simple minimisation procedure; errors on the parameters are derived by scanning the likelihood hyper-surfaces with a wide range of starting values. The metho...

  15. Applications for edge detection techniques using Chandra and XMM-Newton data: galaxy clusters and beyond

    CERN Document Server

    Walker, S A; Fabian, A C

    2016-01-01

    The unrivalled spatial resolution of the Chandra X-ray observatory has allowed many breakthroughs to be made in high energy astrophysics. Here we explore applications of Gaussian Gradient Magnitude (GGM) filtering to X-ray data, which dramatically improves the clarity of surface brightness edges in X-ray observations, and maps gradients in X-ray surface brightness over a range of spatial scales. In galaxy clusters, we find that this method is able to reveal remarkable substructure behind the cold fronts in Abell 2142 and Abell 496, possibly the result of Kelvin Helmholtz instabilities. In Abell 2319 and Abell 3667, we demonstrate that the GGM filter can provide a straightforward way of mapping variations in the widths and jump ratios along the lengths of cold fronts. We present results from our ongoing programme of analysing the Chandra and XMM-Newton archives with the GGM filter. In the Perseus cluster we identify a previously unseen edge around 850 kpc from the core to the east, lying outside a known large ...

  16. High-Resolution Chandra X-ray Imaging and Spectroscopy of the Sigma Orionis Cluster

    CERN Document Server

    Skinner, S L; Cohen, D H; Gagné, M; Owocki, S P; Townsend, R D

    2008-01-01

    We present results of a 90 ksec Chandra X-ray observation of the young sigma Orionis cluster (age ~3 Myr) obtained with the High Energy Transmission Grating Spectrometer. We use the high resolution grating spectrum and moderate resolution CCD spectrum of the massive central star sigma Ori AB (O9.5V + B0.5V) to test wind shock theories of X-ray emission and also analyze the high spatial resolution zero-order ACIS-S image of the central cluster region. Chandra detected 42 X-ray sources on the primary CCD (ACIS-S3). All but five have near-IR or optical counterparts and about one-fourth are variable. Notable high-mass stellar detections are sigma Ori AB, the magnetic B star sigma Ori E, and the B5V binary HD 37525. Most of the other detections have properties consistent with lower mass K or M-type stars. We present the first X-ray spectrum of the unusual infrared source IRS1 located 3.3 arc-sec north of sigma Ori AB, which is likely an embedded T Tauri star whose disk/envelope is being photoevaporated by sigma Or...

  17. Cosmological Constraints from the Red-Sequence Cluster Survey

    CERN Document Server

    Gladders, M D; Hall, P B; Hoekstra, H; Infante, L; Majumdar, S; Yee, H K C; Gladders, Michael D.; Hall, Patrick B.; Hoekstra, Henk; Infante, Leopoldo; Majumdar, Subhabrata

    2006-01-01

    [abridged] We present a first cosmological analysis of a refined cluster catalog from the Red-Sequence Cluster Survey (RCS). The input cluster sample is derived from 72.07 square degrees of imaging data [...] The catalog contains 956 clusters over 0.35cluster richness and richness error. The calibration of the survey images has been extensively cross-checked against publicly available Sloan Digital Sky Survey imaging [...] We analyze the cluster sample via a general self-calibration technique including scatter in the mass-richness relation [...]. We fit simultaneously for Omega_M and sigma_8, and four parameters describing the calibration of cluster richness to mass, its evolution with redshift, and scatter in the richness-mass relation. The principal goal of this general analysis is to establish the consistency (or lack thereof) between the fitted parameters (both cosmological and cluster mass observables) and available results on both from independent measures. From an unconstraine...

  18. Evolution of star clusters in a cosmological tidal field

    CERN Document Server

    Rieder, Steven; Langelaan, Paul; Makino, Junichiro; McMillan, Stephen L W; Zwart, Simon Portegies

    2013-01-01

    We present a method to couple N-body star cluster simulations to a cosmological tidal field, using the Astrophysical Multipurpose Software Environment. We apply this method to star clusters embedded in the CosmoGrid dark matter-only LambdaCDM simulation. Our star clusters are born at z = 10 (corresponding to an age of the Universe of about 500 Myr) by selecting a dark matter particle and initializing a star cluster with 32,000 stars on its location. We then follow the dynamical evolution of the star cluster within the cosmological environment. We compare the evolution of star clusters in two Milky-Way size haloes with a different accretion history. The mass loss of the star clusters is continuous irrespective of the tidal history of the host halo, but major merger events tend to increase the rate of mass loss. From the selected two dark matter haloes, the halo that experienced the larger number of mergers tends to drive a smaller mass loss rate from the embedded star clusters, even though the final masses of ...

  19. Frontier Fields Clusters: Deep Chandra Observations of the Complex Merger MACS J1149.6+2223

    CERN Document Server

    Ogrean, G A; Jones, C; Forman, W; Dawson, W A; Golovich, N; Andrade-Santos, F; Murray, S S; Nulsen, P; Roediger, E; Zitrin, A; Bulbul, E; Kraft, R; Goulding, A; Umetsu, K; Mroczkowski, T; Bonafede, A; Randall, S; Sayers, J; Churazov, E; David, L; Merten, J; Donahue, M; Mason, B; Rosati, P; Vikhlinin, A; Ebeling, H

    2016-01-01

    The HST Frontier Fields cluster MACS J1149.6+2223 is one of the most complex merging clusters, believed to consist of four dark matter halos. We present results from deep (365 ks) Chandra observations of the cluster, which reveal the most distant cold front (z=0.544) discovered to date. In the cluster outskirts, we also detect hints of a surface brightness edge that could be the bow shock preceding the cold front. The substructure analysis of the cluster identified several components with large relative radial velocities, thus indicating that at least some collisions occur almost along the line of sight. The inclination of the mergers with respect to the plane of the sky poses significant observational challenges at X-ray wavelengths. MACS J1149.6+2223 possibly hosts a steep-spectrum radio halo. If the steepness of the radio halo is confirmed, then the radio spectrum, combined with the relatively regular ICM morphology, could indicate that MACS J1149.6+2223 is an old merging cluster.

  20. Chandra X-Ray Observatory Observation of the High-Redshift Cluster MS 1054-0321

    CERN Document Server

    Jeltema, T E; Bautz, M W; Malm, M R; Donahue, M; Garmire, G P; Jeltema, Tesla E.; Canizares, Claude R.; Bautz, Mark W.; Malm, Michael R.; Donahue, Megan; Garmire, Gordon P.

    2001-01-01

    We observed MS 1054-0321, the highest redshift cluster of galaxies in the Einstein Medium Sensitivity Survey (EMSS), with the Chandra ACIS-S detector. We find the X-ray temperature of the cluster to be 10.4 +1.7 -1.5 keV, lower than, but statistically consistent with, the temperature inferred previously. This temperature agrees well with the observed velocity dispersion and that found from weak lensing. We are also able to make the first positive identification of an iron line in this cluster and find a value of 0.26 +/- 0.15 for the abundance relative to solar, consistent with early enrichment of the ICM. We confirm significant substructure in the form of two distinct clumps in the X-ray distribution. The eastern clump seems to coincide with the main cluster component. It has a temperature of 10.5 +3.4 -2.1 keV, approximately the same as the average spectral temperature for the whole cluster. The western clump is cooler, with a temperature of 6.7 +1.7 -1.2 and may be a subgroup falling into the cluster. Thou...

  1. Chandra observation of two shock fronts in the merging galaxy cluster Abell 2146

    CERN Document Server

    Russell, H R; Fabian, A C; Baum, S A; Donahue, M; Edge, A C; McNamara, B R; O'Dea, C P

    2010-01-01

    We present a new Chandra observation of the galaxy cluster Abell 2146 which has revealed a complex merging system with a gas structure that is remarkably similar to the Bullet cluster (eg. Markevitch et al. 2002). The X-ray image and temperature map show a cool 2-3 keV subcluster with a ram pressure stripped tail of gas just exiting the disrupted 6-7 keV primary cluster. From the sharp jump in the temperature and density of the gas, we determine that the subcluster is preceded by a bow shock with a Mach number M=2.2+/-0.8, corresponding to a velocity v=2200^{+1000}_{-900} km/s relative to the main cluster. We estimate that the subcluster passed through the primary core only 0.1-0.3 Gyr ago. In addition, we observe a slower upstream shock propagating through the outer region of the primary cluster and calculate a Mach number M=1.7+/-0.3. Based on the measured shock Mach numbers M~2 and the strength of the upstream shock, we argue that the mass ratio between the two merging clusters is between 3 and 4 to one. B...

  2. A wide Chandra view of the core of the Perseus cluster

    CERN Document Server

    Fabian, A C; Allen, S W; Canning, R E A; Churazov, E; Crawford, C S; Forman, W; GaBany, J; Hlavacek-Larrondo, J; Johnstone, R M; Russell, H R; Reynolds, C S; Salome, P; Taylor, G B; Young, A J

    2011-01-01

    We present new Chandra images of the X-ray emission from the core of the Perseus cluster of galaxies. The total observation time is now 1.4 Ms. New depressions in X-ray surface brightness are discovered to the north of NGC1275, which we interpret as old rising bubbles. They imply that bubbles are long-lived and do not readily breakup when rising in the hot cluster atmosphere. The existence of a 300 kpc long NNW-SSW bubble axis means there cannot be significant transverse large scale flows exceeding 100 km/s. Interesting spatial correlations are seen along that axis in early deep radio maps. A semi-circular cold front about 100 kpc west of the nucleus is seen. It separates an inner disturbed region dominated by the activity of the active nucleus of NGC1275 from the outer region where a subcluster merger dominates.

  3. X-ray Clusters of Galaxies as Cosmological Tools

    CERN Document Server

    Gioia, Isabella Maria

    2009-01-01

    This paper was written as part of a book entitled: "Questions of Modern Cosmology - Galileo's Legacy" which is a celebrative book dedicated to Galileo Galilei. The book is published in 2009, the International Year of Astronomy, since it is intended to be a modern tribute to the astronomer who, 400 years ago, first pointed a telescope towards the night sky. The book is written in the form of interviews between the editors and many physicists, astrophysicists and cosmologists from all over the world. The editors engaged in several discussions on the formation and evolution of the Universe with the aim of summarizing the most important and significative advances made by cosmology over the past century and at the beginning of the new millennium. This paper deals with X-ray clusters of galaxies and how they can be used to constrain fundamental cosmological parameters.

  4. Clusters, Groups, and Filaments in the Chandra Deep Field-South up to Redshift 1

    CERN Document Server

    Dehghan, Siamak

    2013-01-01

    We present a comprehensive structure detection analysis of the 0.3 square degree area of the MUSYC-ACES field which covers the Chandra Deep Field-South (CDFS). Using a density-based clustering algorithm on the MUSYC and ACES photometric and spectroscopic catalogues we find 62 over-dense regions up to redshifts of 1, including, clusters, groups and filaments. All structures are confirmed using the DBSCAN method, including the detection of nine structures previously reported in the literature. We present a catalogue of all structures present including their central position, mean redshift, velocity dispersions, and classification based on their morphological and spectroscopic distributions. In particular we find 13 galaxy clusters and 6 large groups/small clusters. Comparison of these massive structures with published XMM-Newton imaging (where available) shows that $80\\%$ of these structures are associated with diffuse, soft-band (0.4 - 1 keV) X-ray emission including $90\\%$ of all objects classified as cluster...

  5. A Chandra and Spitzer census of the young star cluster in the reflection nebula NGC 7129

    CERN Document Server

    Stelzer, B

    2009-01-01

    The reflection nebula NGC 7129 has long been known to be a site of recent star formation as evidenced, e.g., by the presence of deeply embedded protostars and HH objects. However, studies of the stellar population produced in the star formation process have remained rudimentary. At a presumed age of ~3 Myr, NGC7129 is in the critical range where disks around young stars disappear. We make use of Chandra X-ray and Spitzer and 2MASS IR imaging observations to identify the pre-main sequence stars in NGC7129. We define a sample of Young Stellar Objects based on color-color diagrams composed from IR photometry between 1.6 and 8 mu, from 2MASS and Spitzer, and based on X-ray detected sources from a Chandra observation. This sample is composed of 26 Class II and 25 Class III candidates. The sample is estimated to be complete down to ~ 0.5 solar masses. The most restricted and least biased sub-sample of pre-main sequence stars is composed of lightly absorbed (A_V < 5 mag) stars in the cluster core. This sample com...

  6. Are there cool-core clusters at high-redshift? Chandra results and prospects with WFXT

    CERN Document Server

    Santos, Joana S; Rosati, Piero

    2010-01-01

    In this contribution we trace the evolution of cool-core clusters out to z~1.3 using high-resolution Chandra data of three representative cluster samples spanning different redshift ranges. Our analysis is based on the measurement of the surface brightness (SB) concentration, c_SB, which strongly anti-correlates with the central cooling time and allows us to characterize the cool-core strength in low S/N data. We confirm a negative evolution in the fraction of cool-core clusters with redshift, in particular for very strong cool-cores. Still, we find evidence for a large population of well formed cool-cores at z ~ 1. This analysis is potentially very effective in constraining the nature and the evolution of the cool-cores, once large samples of high-z clusters will be available. In this respect, we explore the potential of the proposed mission Wide Field X-ray Telescope (WFXT) to address this science case. We conclude that WFXT provides the best trade-off of angular resolution, sensitivity and covered solid an...

  7. MOG Weak Field Approximation: A Modified Gravity Compatible with Chandra X-ray Clusters

    CERN Document Server

    Moffat, J W

    2013-01-01

    We use the covariant Scalar-Vector-Tensor theory of gravity (so-called MOG), in the weak field approximation limit to study the dynamics of clusters of galaxies. The ionized gas density and the temperature profile of the clusters are our observables, which have been measured by the Chandra telescope for the nearby clusters. The MOG effective gravitational potential in the weak field approximation is composed of attractive Newtonian and repulsive Yukawa terms. Two parameters $\\alpha$ and $\\mu$ in the effective potential determine the asymptotic gravitational constant and the mass of the vector field, respectively. These parameters have been fixed by fitting MOG dynamics to the rotation curves of galaxies. Our analysis shows that the internal dynamics of clusters can be well explained within $1\\sigma$ with a virial theorem in the framework of MOG, such that the best fit for the ratio of the dynamical mass to the baryonic mass is: $M_{\\rm dyn}/M_{\\rm b} = 0.98^{+0.02}_{-0.02}$. This result means that MOG is a th...

  8. Adaptive Techniques for Clustered N-Body Cosmological Simulations

    CERN Document Server

    Menon, Harshitha; Zheng, Gengbin; Jetley, Pritish; Kale, Laxmikant; Quinn, Thomas; Governato, Fabio

    2014-01-01

    ChaNGa is an N-body cosmology simulation application implemented using Charm++. In this paper, we present the parallel design of ChaNGa and address many challenges arising due to the high dynamic ranges of clustered datasets. We focus on optimizations based on adaptive techniques for scaling to more than 128K cores. We demonstrate strong scaling on up to 512K cores of Blue Waters evolving 12 and 24 billion particles. We also show strong scaling of highly clustered datasets on up to 128K cores.

  9. Galaxy clusters as probes for cosmology and dark matter

    CERN Document Server

    Battistelli, Elia S; de Bernardis, Paolo; Kirillov, Alexander A; Neto, Gastao B Lima; Masi, Silvia; Norgaard-Nielsen, Hans U; Ostermann, Peter; Roman, Matthieu; Rosati, Piero; Rossetti, Mariachiara

    2016-01-01

    In recent years, significant progress has been made in building new galaxy clusters samples, at low and high redshifts, from wide-area surveys, particularly exploiting the Sunyaev--Zel'dovich (SZ) effect. A large effort is underway to identify and characterize these new systems with optical/NIR and X-ray facilities, thus opening new avenues to constraint cosmological models using structure growth and geometrical tests. A census of galaxy clusters sets constraints on reionization mechanisms and epochs, which need to be reconciled with recent limits on the reionization optical depth from cosmic microwave background (CMB) experiments. Future advances in SZ effect measurements will include the possibility to (unambiguously) measure directly the kinematic SZ effect, to build an even larger catalogue of galaxy clusters able to study the high redshift universe, and to make (spatially-)resolved galaxy cluster maps with even spectral capability to (spectrally-)resolve the relativistic corrections of the SZ effect.

  10. Astrophysics and cosmology with galaxy clusters: the WFXT perspective

    CERN Document Server

    Borgani, S; Sartoris, B; Tozzi, P; Giacconi, R

    2010-01-01

    We discuss the central role played by the X-ray study of hot baryons within galaxy clusters to reconstruct the assembly of cosmic structures and to trace the past history of star formation and accretion onto supermassive Black Holes (BHs). We shortly review the progress in this field contributed by the current generation of X-ray telescopes. Then, we focus on the outstanding scientific questions that have been opened by observations carried out in the last years and that represent the legacy of Chandra and XMM: (a) When and how is entropy injected into the inter-galactic medium (IGM)? (b) What is the history of metal enrichment of the IGM? (c) What physical mechanisms determine the presence of cool cores in galaxy clusters? (d) How is the appearance of proto-clusters at z~2 related to the peak of star formation activity and BH accretion? (e) What do galaxy clusters tell us about the nature of primordial density perturbations and on the history of their growth? We show that the most efficient observational str...

  11. A very deep Chandra view of metals, sloshing and feedback in the Centaurus cluster of galaxies

    CERN Document Server

    Sanders, J S; Taylor, G B; Russell, H R; Blundell, K M; Canning, R E A; Hlavacek-Larrondo, J; Walker, S A; Grimes, C K

    2016-01-01

    We examine deep Chandra X-ray observations of the Centaurus cluster of galaxies, Abell 3526. Applying a gradient magnitude filter reveals a wealth of structure, from filamentary soft emission on 100pc (0.5 arcsec) scales close to the nucleus to features 10s of kpc in size at larger radii. The cluster contains multiple high-metallicity regions with sharp edges. Relative to an azimuthal average, the deviations of metallicity and surface brightness are correlated, and the temperature is inversely correlated, as expected if the larger scale asymmetries in the cluster are dominated by sloshing motions. Around the western cold front are a series of ~7 kpc 'notches', suggestive of Kelvin-Helmholtz instabilities. The cold front width varies from 4 kpc down to close to the electron mean free path. Inside the front are multiple metallicity blobs on scales of 5-10 kpc, which could have been uplifted by AGN activity, also explaining the central metallicity drop and flat inner metallicity profile. Close to the nucleus are...

  12. The Dark Matter Halos of Massive, Relaxed Galaxy Clusters Observed With Chandra

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Robert W.; /Heidelberg, Astron. Rechen Inst.; Allen, S.W.; /KIPAC, Menlo Park

    2006-10-11

    We use the Chandra X-ray Observatory to study the dark matter halos of 34 massive, dynamically relaxed galaxy clusters, spanning the redshift range 0.06 < z < 0.7. The observed dark matter and total mass (dark-plus-luminous matter) profiles can be approximated by the Navarro Frenk & White (hereafter NFW) model for cold dark matter (CDM) halos; for {approx} 80 percent of the clusters, the NFW model provides a statistically acceptable fit. In contrast, the singular isothermal sphere model can, in almost every case, be completely ruled out. We observe a well-defined mass-concentration relation for the clusters with a normalization and intrinsic scatter in good agreement with the predictions from simulations. The slope of the mass-concentration relation, c {infinity} M{sub vir}{sup a}/(1 + z){sup b} with a = -0.41 {+-} 0.11 at 95 percent confidence, is steeper than the value a {approx} -0.1 predicted by CDM simulations for lower mass halos. With the slope a included as a free fit parameter, the redshift evolution of the concentration parameter, b = 0.54 {+-} 0.47 at 95 percent confidence, is also slower than, but marginally consistent with, the same simulations (b {approx} 1). Fixing a {approx} -0.1 leads to an apparent evolution that is significantly slower, b = 0.20 {+-} 0.45, although the goodness of fit in this case is significantly worse. Using a generalized NFW model, we find the inner dark matter density slope, a, to be consistent with unity at 95 percent confidence for the majority of clusters. Combining the results for all clusters for which the generalized NFW model provides a good description of the data, we measure ? = 0.88 {+-} 0.29 at 95 percent confidence, in agreement with CDM model predictions.

  13. Clusters, groups, and filaments in the Chandra deep field-south up to redshift 1

    Energy Technology Data Exchange (ETDEWEB)

    Dehghan, S.; Johnston-Hollitt, M., E-mail: siamak.dehghan@vuw.ac.nz [School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140 (New Zealand)

    2014-03-01

    We present a comprehensive structure detection analysis of the 0.3 deg{sup 2} area of the MUSYC-ACES field, which covers the Chandra Deep Field-South (CDFS). Using a density-based clustering algorithm on the MUSYC and ACES photometric and spectroscopic catalogs, we find 62 overdense regions up to redshifts of 1, including clusters, groups, and filaments. We also present the detection of a relatively small void of ∼10 Mpc{sup 2} at z ∼ 0.53. All structures are confirmed using the DBSCAN method, including the detection of nine structures previously reported in the literature. We present a catalog of all structures present, including their central position, mean redshift, velocity dispersions, and classification based on their morphological and spectroscopic distributions. In particular, we find 13 galaxy clusters and 6 large groups/small clusters. Comparison of these massive structures with published XMM-Newton imaging (where available) shows that 80% of these structures are associated with diffuse, soft-band (0.4-1 keV) X-ray emission, including 90% of all objects classified as clusters. The presence of soft-band X-ray emission in these massive structures (M {sub 200} ≥ 4.9 × 10{sup 13} M {sub ☉}) provides a strong independent confirmation of our methodology and classification scheme. In the closest two clusters identified (z < 0.13) high-quality optical imaging from the Deep2c field of the Garching-Bonn Deep Survey reveals the cD galaxies and demonstrates that they sit at the center of the detected X-ray emission. Nearly 60% of the clusters, groups, and filaments are detected in the known enhanced density regions of the CDFS at z ≅ 0.13, 0.52, 0.68, and 0.73. Additionally, all of the clusters, bar the most distant, are found in these overdense redshift regions. Many of the clusters and groups exhibit signs of ongoing formation seen in their velocity distributions, position within the detected cosmic web, and in one case through the presence of tidally

  14. Clusters, groups, and filaments in the Chandra deep field-south up to redshift 1

    International Nuclear Information System (INIS)

    We present a comprehensive structure detection analysis of the 0.3 deg2 area of the MUSYC-ACES field, which covers the Chandra Deep Field-South (CDFS). Using a density-based clustering algorithm on the MUSYC and ACES photometric and spectroscopic catalogs, we find 62 overdense regions up to redshifts of 1, including clusters, groups, and filaments. We also present the detection of a relatively small void of ∼10 Mpc2 at z ∼ 0.53. All structures are confirmed using the DBSCAN method, including the detection of nine structures previously reported in the literature. We present a catalog of all structures present, including their central position, mean redshift, velocity dispersions, and classification based on their morphological and spectroscopic distributions. In particular, we find 13 galaxy clusters and 6 large groups/small clusters. Comparison of these massive structures with published XMM-Newton imaging (where available) shows that 80% of these structures are associated with diffuse, soft-band (0.4-1 keV) X-ray emission, including 90% of all objects classified as clusters. The presence of soft-band X-ray emission in these massive structures (M 200 ≥ 4.9 × 1013 M ☉) provides a strong independent confirmation of our methodology and classification scheme. In the closest two clusters identified (z < 0.13) high-quality optical imaging from the Deep2c field of the Garching-Bonn Deep Survey reveals the cD galaxies and demonstrates that they sit at the center of the detected X-ray emission. Nearly 60% of the clusters, groups, and filaments are detected in the known enhanced density regions of the CDFS at z ≅ 0.13, 0.52, 0.68, and 0.73. Additionally, all of the clusters, bar the most distant, are found in these overdense redshift regions. Many of the clusters and groups exhibit signs of ongoing formation seen in their velocity distributions, position within the detected cosmic web, and in one case through the presence of tidally disrupted central galaxies

  15. Weak Lensing by Galaxy Clusters: from Pixels to Cosmology

    International Nuclear Information System (INIS)

    The story of the origin and evolution of our Universe is told, equivalently, by space-time itself and by the structures that grow inside of it. Clusters of galaxies are the frontier of bottom-up structure formation. They are the most massive objects to have collapsed at the present epoch. By that virtue, their abundance and structural parameters are highly sensitive to the composition and evolution of the Universe. The most common probe of cluster cosmology, abundance, uses samples of clusters selected by some observable. Applying a mass-observable relation (MOR), cosmological parameters can be constrained by comparing the sample to predicted cluster abundances as a function of observable and redshift. Arguably, however, cluster probes have not yet entered the era of per cent level precision cosmology. The primary reason for this is our imperfect understanding of the MORs. The overall normalization, the slope of mass vs. observable, the redshift evolution, and the degree and correlation of intrinsic scatters of observables at fixed mass have to be constrained for interpreting abundances correctly. Mass measurement of clusters by means of the differential deflection of light from background sources in their gravitational field, i.e. weak lensing, is a powerful approach for achieving this. This thesis presents new methods for and scientific results of weak lensing measurements of clusters of galaxies. The former include, on the data reduction side, (i) the correction of CCD images for non-linear effects due to the electric fields of accumulated charges and (ii) a method for masking artifact features in sets of overlapping images of the sky by comparison to the median image. Also, (iii) I develop a method for the selection of background galaxy samples based on their color and apparent magnitude that includes a new correction for contamination with cluster member galaxies. The main scientific results are the following. (i) For the Hubble Frontier Field cluster RXC J

  16. Weak Lensing by Galaxy Clusters: from Pixels to Cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Gruen, Daniel [Ludwig Maximilian Univ., Munich (Germany)

    2015-03-11

    The story of the origin and evolution of our Universe is told, equivalently, by space-time itself and by the structures that grow inside of it. Clusters of galaxies are the frontier of bottom-up structure formation. They are the most massive objects to have collapsed at the present epoch. By that virtue, their abundance and structural parameters are highly sensitive to the composition and evolution of the Universe. The most common probe of cluster cosmology, abundance, uses samples of clusters selected by some observable. Applying a mass-observable relation (MOR), cosmological parameters can be constrained by comparing the sample to predicted cluster abundances as a function of observable and redshift. Arguably, however, cluster probes have not yet entered the era of per cent level precision cosmology. The primary reason for this is our imperfect understanding of the MORs. The overall normalization, the slope of mass vs. observable, the redshift evolution, and the degree and correlation of intrinsic scatters of observables at fixed mass have to be constrained for interpreting abundances correctly. Mass measurement of clusters by means of the differential deflection of light from background sources in their gravitational field, i.e. weak lensing, is a powerful approach for achieving this. This thesis presents new methods for and scientific results of weak lensing measurements of clusters of galaxies. The former include, on the data reduction side, (i) the correction of CCD images for non-linear effects due to the electric fields of accumulated charges and (ii) a method for masking artifact features in sets of overlapping images of the sky by comparison to the median image. Also, (iii) I develop a method for the selection of background galaxy samples based on their color and apparent magnitude that includes a new correction for contamination with cluster member galaxies. The main scientific results are the following. (i) For the Hubble Frontier Field cluster RXC J

  17. Thermodynamic perturbations in the X-ray halo of 33 clusters of galaxies observed with Chandra ACIS

    CERN Document Server

    Hofmann, F; Nandra, K; Clerc, N; Gaspari, M

    2016-01-01

    In high-resolution X-ray observations of the hot plasma in clusters of galaxies significant structures caused by AGN feedback, mergers, and turbulence can be detected. Many clusters have been observed by Chandra in great depth and at high resolution. Using archival data taken with the Chandra ACIS instrument the aim was to study thermodynamic perturbations of the X-ray emitting plasma and to apply this to better understand the thermodynamic and dynamic state of the intra cluster medium (ICM). We analysed deep observations for a sample of 33 clusters with more than 100 ks of Chandra exposure each at distances between redshift 0.025 and 0.45. The combined exposure of the sample is 8 Ms. Fitting emission models to different regions of the extended X-ray emission we searched for perturbations in density, temperature, pressure, and entropy of the hot plasma. For individual clusters we mapped the thermodynamic properties of the ICM and measured their spread in circular concentric annuli. Comparing the spread of dif...

  18. Deep Chandra observation and numerical studies of the nearest cluster cold front in the sky

    CERN Document Server

    Werner, N; Zhuravleva, I; Ichinohe, Y; Simionescu, A; Allen, S W; Markevitch, M; Fabian, A C; Keshet, U; Roediger, E; Ruszkowski, M; Sanders, J S

    2015-01-01

    We present the results of a very deep (500 ks) Chandra observation, along with tailored numerical simulations, of the nearest, best resolved cluster cold front in the sky, which lies 90 kpc (19 arcmin) to the northwest of M 87. The northern part of the front appears the sharpest, with a width smaller than 2.5 kpc (1.5 Coulomb mean free paths; at 99 per cent confidence). Everywhere along the front, the temperature discontinuity is narrower than 4-8 kpc and the metallicity gradient is narrower than 6 kpc, indicating that diffusion, conduction and mixing are suppressed across the interface. Such transport processes can be naturally suppressed by magnetic fields aligned with the cold front. However, the northwestern part of the cold front is observed to have a nonzero width. The broadening is consistent with the presence of Kelvin-Helmholtz instabilities (KHI) on length scales of a few kpc. Based on comparison with simulations, the presence of KHI would imply that the effective viscosity of the intra-cluster medi...

  19. The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected via the Sunyaev-Zel'dovich Effect

    Energy Technology Data Exchange (ETDEWEB)

    Sehgal, Neelima; Trac, Hy; Acquaviva, Viviana; Ade, Peter A.R.; Aguirre, Paula; Amiri, Mandana; Appel, John W.; Barrientos, L.Felipe; Battistelli, Elia S.; Bond, J.Richard; Brown, Ben; Burger, Bryce; Chervenak, Jay; Das, Sudeep; Devlin, Mark J.; Dicker, Simon R.; Doriese, W.Bertrand; Dunkley, Joanna; Dunner, Rolando; Essinger-Hileman, Thomas; Fisher, Ryan P.

    2011-08-18

    We present constraints on cosmological parameters based on a sample of Sunyaev-Zeldovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives {sigma}{sub 8} = 0.851 {+-} 0.115 and w = -1.14 {+-} 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find {sigma}{sub 8} = 0.821 {+-} 0.044 and w = -1.05 {+-} 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernoava which give {sigma}{sub 8} = 0.802 {+-} 0.038 and w = -0.98 {+-} 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.

  20. A very deep Chandra view of metals, sloshing and feedback in the Centaurus cluster of galaxies

    Science.gov (United States)

    Sanders, J. S.; Fabian, A. C.; Taylor, G. B.; Russell, H. R.; Blundell, K. M.; Canning, R. E. A.; Hlavacek-Larrondo, J.; Walker, S. A.; Grimes, C. K.

    2016-03-01

    We examine deep Chandra X-ray observations of the Centaurus cluster of galaxies, Abell 3526. Applying a gradient magnitude filter reveals a wealth of structure, from filamentary soft emission on 100 pc (0.5 arcsec) scales close to the nucleus to features 10 s of kpc in size at larger radii. The cluster contains multiple high-metallicity regions with sharp edges. Relative to an azimuthal average, the deviations of metallicity and surface brightness are correlated, and the temperature is inversely correlated, as expected if the larger scale asymmetries in the cluster are dominated by sloshing motions. Around the western cold front are a series of ˜7 kpc `notches', suggestive of Kelvin-Helmholtz instabilities. The cold front width varies from 4 kpc down to close to the electron mean free path. Inside the front are multiple metallicity blobs on scales of 5-10 kpc, which could have been uplifted by AGN activity, also explaining the central metallicity drop and flat inner metallicity profile. Close to the nucleus are multiple shocks, including a 1.9-kpc-radius inner shell-like structure and a weak 1.1-1.4 Mach number shock around the central cavities. Within a 10 kpc radius are nine depressions in surface brightness, several of which appear to be associated with radio emission. The shocks and cavities imply that the nucleus has been repeatedly active on 5-10 Myr time-scales, indicating a tight balance between heating and cooling. We confirm the presence of a series of linear quasi-periodic structures. If they are sound waves, the ˜5 kpc spacing implies a period of 6 Myr, similar to the ages of the shocks and cavities. Alternatively, these structures may be Kelvin-Helmholtz instabilities, their associated turbulence or amplified magnetic field layers.

  1. Galaxy cluster number count data constraints on cosmological parameters

    Energy Technology Data Exchange (ETDEWEB)

    Campanelli, L. [Universita di Bari, Dipartimento di Fisica, Bari (Italy); Fogli, G.L.; Marrone, A. [Universita di Bari, Dipartimento di Fisica, Bari (Italy); INFN-Sezione di Bari, Bari (Italy); Kahniashvili, T. [Carnegie Mellon University, McWilliams Center for Cosmology and Department of Physics, Pittsburgh, PA (United States); Laurentian University, Department of Physics, Sudbury, ON (Canada); Ilia State University, Abastumani Astrophysical Observatory, Tbilisi (Georgia); Ratra, Bharat [Kansas State University, Department of Physics, Manhattan, KS (United States)

    2012-11-15

    We use data on massive galaxy clusters (M{sub cluster}>8 x 10{sup 14} h{sup -1} M{sub s}un within a comoving radius of R{sub cluster}=1.5h{sup -1} Mpc) in the redshift range 0.05cosmology of the quantities related to cluster physics: the critical density contrast, the growth factor, the mass conversion factor, the virial overdensity, the virial radius and, most importantly, the cluster number count derived from the observational temperature data. We show that, contrary to previous analyses, cluster data alone prefer low values of the amplitude of mass fluctuations, {sigma}{sub 8}{<=}0.69 (1 {sigma} C.L.), and large amounts of nonrelativistic matter, {Omega}{sub m} {>=}0.38 (1 {sigma} C.L.), in slight tension with the {Lambda}CDM concordance cosmological model, though the results are compatible with {Lambda}CDM at 2 {sigma}. In addition, we derive a {sigma}{sub 8} normalization relation, {sigma}{sub 8}{Omega}{sub m}{sup 1/3} = 0.49 {+-} 0.06 (2{sigma} C.L.). Combining cluster data with {sigma}{sub 8}-independent baryon acoustic oscillation observations, cosmic microwave background data, Hubble constant measurements, Hubble parameter determination from passively evolving red galaxies, and magnitude-redshift data of type Ia supernovae, we find {Omega}{sub m} = 0.28{sup +0.03}{sub -0.02} and {sigma}{sub 8} = 0.73{sup +0.03}{sub -0.03}, the former in agreement and the latter being slightly lower than the corresponding values in the concordance cosmological model. We also find H{sub 0} = 69.1{sup +1

  2. Optically-Selected Cluster Catalogs As a Precision Cosmology Tool

    Energy Technology Data Exchange (ETDEWEB)

    Rozo, Eduardo; /Ohio State U. /Chicago U. /KICP, Chicago; Wechsler, Risa H.; /KICP, Chicago /KIPAC, Menlo Park; Koester, Benjamin P.; /Michigan U. /Chicago U., Astron.; Evrard, August E.; McKay, Timothy A.; /Michigan U.

    2007-03-26

    We introduce a framework for describing the halo selection function of optical cluster finders. We treat the problem as being separable into a term that describes the intrinsic galaxy content of a halo (the Halo Occupation Distribution, or HOD) and a term that captures the effects of projection and selection by the particular cluster finding algorithm. Using mock galaxy catalogs tuned to reproduce the luminosity dependent correlation function and the empirical color-density relation measured in the SDSS, we characterize the maxBCG algorithm applied by Koester et al. to the SDSS galaxy catalog. We define and calibrate measures of completeness and purity for this algorithm, and demonstrate successful recovery of the underlying cosmology and HOD when applied to the mock catalogs. We identify principal components--combinations of cosmology and HOD parameters--that are recovered by survey counts as a function of richness, and demonstrate that percent-level accuracies are possible in the first two components, if the selection function can be understood to {approx} 15% accuracy.

  3. Chandra X-Ray Observations of Young Clusters. III. NGC 2264 and the Orion Flanking Fields

    CERN Document Server

    Rebull, L M; Micela, G; Ramírez, S V; Sciortino, S; Stauffer, J R; Strom, S E; Wolff, S C

    2006-01-01

    Chandra observations of solar-like pre-main sequence (PMS) stars in the Orion Flanking Fields (age ~1 Myr) and NGC 2264 (~3 Myr) are compared with the results of the COUP survey of similar objects in the ONC (~0.5 Myr). The correlations between log Lx and mass found for PMS stars on convective tracks in these clusters are consistent with the relationships found for the ONC, indicating little change in the median values of either log Lx or log Lx/Lbol during the first ~3-5 Myr of evolution down convective tracks. The fraction of stars with extreme values of Lx, more than 10 times higher than the average for a given Lbol or with log Lx/Lbol greater than the canonical saturation value of -2.9, is however larger by a factor of two in the younger ONC when compared with the Orion FF and NGC 2264. PMS stars in NGC 2264 on radiative tracks have Lx/Lbol values that are systematically lower by a factor of ~10 times than those found for stars of similar mass on convective tracks. The dramatic decrease in flux from conve...

  4. Chandra Imaging of the X-ray Core of the Virgo Cluster

    CERN Document Server

    Young, A J; Mundell, C G

    2002-01-01

    We report sub-arcsecond X-ray imaging spectroscopy of M87 and the core of the Virgo cluster with the Chandra X-ray Observatory. The X-ray morphology shows structure on arcsecond (~100 pc) to ten arcminute (~50 kpc) scales, the most prominent feature being an "arc" running from the east, across the central region of M87 and off to the southwest. A ridge in the radio map, ending in an "ear"-shaped structure, follows the arc to the east, and the radio emission appears to be wrapped around the arc to the southwest. Depressions in the X-ray surface brightness correspond to the inner radio lobes. There are also at least two approximately circular (centered near the nucleus) "edges" in the X-ray brightness distribution, the radii of which are similar to the nuclear distances of the inner radio lobes and intermediate radio ridges. We speculate that these discontinuities may be spherical pulses or "fronts" driven by the same jet activity as is responsible for the radio structure; such pulses are found in recent numeri...

  5. Radio and Deep Chandra Observations of the Disturbed Cool Core Cluster Abell 133

    CERN Document Server

    Randall, S W; Nulsen, P E J; Owers, M S; Sarazin, C L; Forman, W R; Murray, S S

    2010-01-01

    We present results based on new Chandra and multi-frequency radio observations of the disturbed cool core cluster Abell 133. The diffuse gas has a complex bird-like morphology, with a plume of emission extending from two symmetric wing-like features, and capped with a filamentary radio relic. X-ray observations indicate the presence of either high temperature gas or non-thermal emission in the region of the relic. We find evidence for a weak elliptical X-ray surface brightness edge surrounding the core, consistent with a sloshing cold front. The plume is consistent with having formed due to uplift by a buoyantly rising radio bubble, now seen as the radio relic. Our results are inconsistent with the previous suggestion that the X-ray wings formed due to the passage of a weak shock through the cool core. We instead conclude that the wings are due to X-ray cavities formed by gas displacement by the radio relic. The central cD galaxy contains two small-scale cold gas clumps that are slightly offset from their opt...

  6. CHANDRA DETECTION OF X-RAY EMISSION FROM ULTRACOMPACT DWARF GALAXIES AND EXTENDED STAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Meicun; Li, Zhiyuan, E-mail: lizy@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210046 (China)

    2016-03-10

    We have conducted a systematic study of X-ray emission from ultracompact dwarf (UCD) galaxies and extended star clusters (ESCs), based on archival Chandra observations. Among a sample of 511 UCDs and ESCs complied from the literature, 17 X-ray counterparts with 0.5–8 keV luminosities above ∼5 × 10{sup 36} erg s{sup −1} are identified, which are distributed in eight early-type host galaxies. To facilitate comparison, we also identify X-ray counterparts of 360 globular clusters (GCs) distributed in four of the eight galaxies. The X-ray properties of the UCDs and ESCs are found to be broadly similar to those of the GCs. The incidence rate of X-ray-detected UCDs and ESCs, 3.3% ± 0.8%, while lower than that of the X-ray-detected GCs (7.0% ± 0.4%), is substantially higher than expected from the field populations of external galaxies. A stacking analysis of the individually undetected UCDs/ESCs further reveals significant X-ray signals, which corresponds to an equivalent 0.5–8 keV luminosity of ∼4 × 10{sup 35} erg s{sup −1} per source. Taken together, these provide strong evidence that the X-ray emission from UCDs and ESCs is dominated by low-mass X-ray binaries having formed from stellar dynamical interactions, consistent with the stellar populations in these dense systems being predominantly old. For the most massive UCDs, there remains the possibility that a putative central massive black hole gives rise to the observed X-ray emission.

  7. Chandra ACIS-S Observations of Abell 4059 Signs of Dramatic Interaction Between a Radio Galaxy and a Galaxy Cluster

    CERN Document Server

    Heinz, S; Reynolds, C S; Begelman, M C; Heinz, Sebastian; Choi, Yun-Young; Reynolds, Christopher S; Begelman, Mitchell C.

    2002-01-01

    We present Chandra observations of the galaxy cluster A4059. We find strong evidence that the FR-I radio galaxy PKS 2354-35 at the center of A4059 is inflating cavities with radii ~20 kpc in the intracluster medium, similar to the situation seen in Perseus A and Hydra A. We also find evidence for interaction between the intracluster medium and PKS 2354-35 on small scales in the very center of the cluster. Arguments are presented suggesting that this radio galaxy has faded significantly in radio power (possibly from an FR-II state) over the past 10^8 yrs.

  8. A Chandra Study of the Image Power Spectra of 41 Cool Core and Non-Cool Core Galaxy Clusters

    CERN Document Server

    Zhang, Chenhao; Zhu, Zhenghao; Li, Weitian; Hu, Dan; Wang, Jingying; Gu, Junhua; Gu, Liyi; Zhang, Zhongli; Liu, Chengze; Zhu, Jie; Wu, Xiang-Ping

    2016-01-01

    In this work we propose a new diagnostic to segregate cool core (CC) clusters from non-cool core (NCC) clusters by studying the two-dimensional power spectra of the X-ray images observed with the Chandra X-ray observatory. Our sample contains 41 members ($z=0.01\\sim 0.54$), which are selected from the Chandra archive when a high photon count, an adequate angular resolution, a relatively complete detector coverage, and coincident CC-NCC classifications derived with three traditional diagnostics are simultaneously guaranteed. We find that in the log-log space the derived image power spectra can be well represented by a constant model component at large wavenumbers, while at small wavenumbers a power excess beyond the constant component appears in all clusters, with a clear tendency that the excess is stronger in CC clusters. By introducing a new CC diagnostic parameter, i.e., the power excess index (PEI), we classify the clusters in our sample and compare the results with those obtained with three traditional C...

  9. Chandra measurements of non-thermal X-ray emission from massive, merging, radio-halo clusters

    CERN Document Server

    Million, E T

    2008-01-01

    We report the discovery of spatially-extended, non-thermal or hot, quasi-thermal emission components in Chandra X-ray spectra for five of a sample of seven massive, merging galaxy clusters with powerful radio halos: Abell 665, 2163, 2255, 2319, and 1E0657-56. The emission components can be fitted by power-law models with mean photon indices in the range 1.4 20 keV. A control sample of regular, dynamically relaxed clusters without radio halos but with comparable thermal temperatures and luminosities shows no evidence for similar components in their Chandra spectra. Detailed X-ray spectral mapping reveals the complex thermodynamic states of the radio halo clusters. We report the discovery of a clear, large-scale shock front in Abell 2219. Our deepest observations, of the Bullet Cluster 1E0657-56, demonstrate a spatial correlation between the strongest power law X-ray emission, highest thermal pressure, and brightest 1.34GHz radio halo emission in this cluster. The integrated flux and mean spectral index of the...

  10. Modeling color-dependent galaxy clustering in cosmological simulations

    CERN Document Server

    Masaki, Shogo; Yoshida, Naoki

    2013-01-01

    We extend the subhalo abundance matching method to assign galaxy color to subhalos. We separate a luminosity-binned subhalo sample into two groups by a secondary subhalo property which is presumed to be correlated with galaxy color. The two subsamples then represent red and blue galaxy populations. We explore two models for the secondary propertty; subhalo assembly time and local dark matter density around each subhalo. The model predictions for the galaxy two-point correlation functions are compared with the recent results from the Sloan Digital Sky Survey. We show that the observed color dependence of galaxy clustering can be reproduced well by our method applied to cosmological N-body simulations without baryonic components. We then compare the model predictions for the color-dependent galaxy-mass cross correlation functions with the results from gravitational lensing observations. The comparison allows us to distinguish the models, and also to discuss what subhalo property should be used to assign color t...

  11. The Atacama Cosmology Telescope: ACT-CL J0102-4215 "El Gordo," a Massive Merging Cluster at Redshift 0.87

    CERN Document Server

    Menanteau, Felipe; Sifon, Cristobal; Hilton, Matt; Gonzalez, Jorge; Infante, Leopoldo; Barrientos, L Felipe; Baker, Andrew J; Das, Sudeep; Devlin, Mark J; Dunkley, Joanna; Hincks, Adam D; Kosowsky, Arthur; Mardsen, Danica; Marriage, Tobias A; Moodley, Kavilan; Niemack, Michael D; Page, Lyman A; Reese, Erik D; Sehgal, Neelima; Sievers, Jon; Spergel, David N; Staggs, Suzanne T; Wollack, Edward

    2011-01-01

    We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich(SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope collaboration discovered it as the most significant SZ decrement in a sky survey area of 755 square degrees. Our VLT/FORS2 spectra of 89 member galaxies yield a cluster redshift, z=0.870, and velocity dispersion, sigma=1321+/-106 km/s. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of Tx=14.5+/-0.1 keV and 0.5-2.0 keV band luminosity of Lx=(2.19+/-0.11) x 10^45 h_70^-2 erg/s. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Yx, and integrated SZ distortion, we estimate a cluster mass of M_200=(2.16+/-0.32)x10^15 M_sun/h_70. The Chandra and VLT/FORS2 optical data also reveal that ACT...

  12. Clustering tomography: measuring cosmological distances through angular clustering in thin redshift shells

    CERN Document Server

    Salazar-Albornoz, Salvador; Padilla, Nelson D; Baugh, Carlton M

    2014-01-01

    We test the cosmological implications of studying galaxy clustering using a tomographic approach, by computing the galaxy two-point angular correlation function $\\omega(\\theta)$ in thin redshift shells using a spectroscopic-redshift galaxy survey. The advantages of this procedure are that it is not necessary to assume a fiducial cosmology in order to convert measured angular positions and redshifts into distances, and that it gives several (less accurate) measurements of the angular diameter distance $D_\\rm{A}(z)$ instead of only one (more precise) measurement of the effective average distance $D_\\rm{V}(z)$, which results in better constraints on the expansion history of the Universe. We test our model for $\\omega(\\theta)$ and its covariance matrix against a set of mock galaxy catalogues and show that this technique is able to extract unbiased cosmological constraints. Also, assuming the best-fit $\\Lambda$CDM cosmology from the cosmic microwave background measurements from the Planck satellite, we forecast th...

  13. Probing cosmological isotropy with Planck Sunyaev-Zeldovich galaxy clusters

    CERN Document Server

    Bengaly,, C A P; Alcaniz, J S; Ferreira, I S

    2015-01-01

    We probe the hypothesis of cosmological isotropy using the Planck Sunyaev-Zeldovich (PSZ) galaxy clusters data set. Our analyses consist on a hemispherical comparison of the clusters angular distribution, searching for a preferred direction in the large-scale structure of the Universe. We obtain a maximal dipolar signal at the direction $(l,b) = (53.44^{\\circ},41.81^{\\circ})$ whose antipode points toward $(l,b) = (233.44^{\\circ},-41.81^{\\circ})$. Interestingly, this antipode is marginally consistent with the anomalous Cold Spot found in the Cosmic Microwave Background, located at $(l,b) \\simeq (209^ {\\circ},-57^ {\\circ})$, which might be possibly aligned with a supervoid at $z \\sim 0.2$ with $\\sim 200 \\; \\mathrm{Mpc/h}$ of radius. The statistical significance of this result is assessed with ensembles of Monte Carlo realisations, finding that only a small number of runs are able to reproduce a close direction to this one, hence rejecting the null hypothesis of such direction being a random fluctuation of the d...

  14. Cosmological tests using redshift space clustering in BOSS DR11

    International Nuclear Information System (INIS)

    We analyze the clustering of large scale structure in the Universe in a model independent method, accounting for anisotropic effects along and transverse to the line of sight. A large sample of 690,000 galaxies from The Baryon Oscillation Spectroscopy Survey Data Release 11 are used to determine the Hubble expansion H, angular distance DA, and growth rate GΘ at an effective redshift of z=0.57. After careful bias and convergence studies of the effects from small scale clustering, we find that cutting transverse separations below 40 Mpc/h delivers robust results while smaller scale data leads to a bias due to unmodelled nonlinear and velocity effects. The converged results are in agreement with concordance ΛCDM cosmology, general relativity, and minimal neutrino mass, all within the 68% confidence level. We also present results separately for the northern and southern hemisphere sky, finding a slight tension in the growth rate --- potentially a signature of anisotropic stress, or just covariance with small scale velocities --- but within 68% CL

  15. Cosmological tests using redshift space clustering in BOSS DR11

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yong-Seon; Oh, Minji; Linder, Eric V. [Korea Astronomy and Space Science Institute, Daejeon, 305-348 (Korea, Republic of); Sabiu, Cristiano G. [Korea Institute for Advanced Study, Dongdaemun-gu, Seoul, 130-722 (Korea, Republic of); Okumura, Teppei, E-mail: ysong@kasi.re.kr, E-mail: csabiu@gmail.com, E-mail: teppei.okumura@ipmu.jp, E-mail: minjioh@kasi.re.kr, E-mail: evlinder@lbl.gov [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo, Chiba, 277-8582 Japan (Japan)

    2014-12-01

    We analyze the clustering of large scale structure in the Universe in a model independent method, accounting for anisotropic effects along and transverse to the line of sight. A large sample of 690,000 galaxies from The Baryon Oscillation Spectroscopy Survey Data Release 11 are used to determine the Hubble expansion H, angular distance D{sub A}, and growth rate G{sub Θ} at an effective redshift of z=0.57. After careful bias and convergence studies of the effects from small scale clustering, we find that cutting transverse separations below 40 Mpc/h delivers robust results while smaller scale data leads to a bias due to unmodelled nonlinear and velocity effects. The converged results are in agreement with concordance ΛCDM cosmology, general relativity, and minimal neutrino mass, all within the 68% confidence level. We also present results separately for the northern and southern hemisphere sky, finding a slight tension in the growth rate --- potentially a signature of anisotropic stress, or just covariance with small scale velocities --- but within 68% CL.

  16. Cosmological Tests using Redshift Space Clustering in BOSS DR11

    CERN Document Server

    Song, Yong-Seon; Okumura, Teppei; Oh, Minji; Linder, Eric V

    2014-01-01

    We analyze the clustering of large scale structure in the Universe in a model independent method, accounting for anisotropic effects along and transverse to the line of sight. The Baryon Oscillation Spectroscopy Survey Data Release 11 provides a large sample of 690,000 galaxies, allowing determination of the Hubble expansion H, angular distance D_A, and growth rate G_T at an effective redshift of z=0.57. After careful bias and convergence studies of the effects from small scale clustering, we find that cutting transverse separations below 40 Mpc/h delivers robust results while smaller scale data leads to a bias due to unmodelled nonlinear and velocity effects. The converged results are in agreement with concordance LCDM cosmology, general relativity, and minimal neutrino mass, all within the 68% confidence level. We also present results separately for the northern and southern hemisphere sky, finding a slight tension in the growth rate -- potentially a signature of anisotropic stress, or just covariance with ...

  17. Age Estimates of Universe: from Globular Clusters to Cosmological Models and Probes

    CERN Document Server

    Fatima, Hira; Rahman, Syed Faisal Ur

    2016-01-01

    We performed the photometric analysis of M2 and M92 globular clusters in g and r bands of SLOAN photometric system. We transformed these g and r bands into BV bands of Johnson-Cousins photometric system and built the color magnitude diagram (CMD). We estimated the age, and metallicity of both the clusters, by fitting Padova isochrones of different age and metallicities onto the CMD. We studied Einstein and de Sitter model, bench mark model, the cosmological parameters by WMAP and Planck surveys. Finally, we compared estimated age of globular clusters to the ages from the cosmological models and cosmological parameters values of WMAP and Planck surveys.

  18. The Atacama Cosmology Telescope: ACT-CL J0102-4915 "El Gordo," a Massive Merging Cluster at Redshift 0.87

    Science.gov (United States)

    Menanteau, Felipe; Hughes, John P.; Sifón, Cristóbal; Hilton, Matt; González, Jorge; Infante, Leopoldo; Barrientos, L. Felipe; Baker, Andrew J.; Bond, John R.; Das, Sudeep; Devlin, Mark J.; Dunkley, Joanna; Hajian, Amir; Hincks, Adam D.; Kosowsky, Arthur; Marsden, Danica; Marriage, Tobias A.; Moodley, Kavilan; Niemack, Michael D.; Nolta, Michael R.; Page, Lyman A.; Reese, Erik D.; Sehgal, Neelima; Sievers, Jon; Spergel, David N.; Staggs, Suzanne T.; Wollack, Edward

    2012-03-01

    We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant SZ decrement in a sky survey area of 755 deg2. Our Very Large Telescope (VLT)/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, σgal = 1321 ± 106 km s-1. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T X = 14.5 ± 0.1 keV and 0.5-2.0 keV band luminosity of L X = (2.19 ± 0.11) × 1045 h -2 70 erg s-1. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y X, and integrated SZ distortion, we estimate a cluster mass of M 200a = (2.16 ± 0.32) × 1015 h -1 70 M ⊙. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6 ± 0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 ± 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102-4915 is possibly a high-redshift analog of the famous Bullet cluster. Such a massive cluster at this redshift is rare, although consistent with the standard

  19. Precision cosmology with a combination of wide and deep Sunyaev-Zeldovich cluster surveys

    CERN Document Server

    Khedekar, Satej; Das, Sudeep

    2010-01-01

    We show the advantages of a wedding cake design for Sunyaev-Zel'dovich cluster surveys. We show that by dividing up a cluster survey into a wide and a deep survey, one can essentially recover the cosmological information that would be diluted in a single survey of the same duration due to the uncertainties in our understanding of cluster physics. The parameter degeneracy directions of the deep and wide surveys are slightly different, and combining them breaks these degeneracies effectively. A variable depth survey with a few thousand clusters is as effective at constraining cosmological parameters as a single depth survey with a much larger cluster sample.

  20. Star cluster formation in cosmological simulations. I. properties of young clusters

    CERN Document Server

    Li, Hui; Gnedin, Nickolay Y; Meng, Xi; Semenov, Vadim A; Kravtsov, Andrey V

    2016-01-01

    We present a new implementation of star formation in cosmological simulations, by considering star clusters as a unit of star formation. Cluster particles grow in mass over several million years at the rate determined by local gas properties, with high time resolution. The particle growth is terminated by its own energy and momentum feedback on the interstellar medium. We test this implementation for Milky Way-sized galaxies at high redshift, by comparing the properties of model clusters with observations of young star clusters. We find that the cluster initial mass function is best described by a Schechter function rather than a single power law. In agreement with observations, at low masses the logarithmic slope is $\\alpha\\approx 1.8-2$, while the cutoff at high mass scales with the star formation rate. A related trend is a positive correlation between the surface density of star formation rate and fraction of stars contained in massive clusters. Both trends indicate that the formation of massive star clust...

  1. Galaxy Clustering & Galaxy-Galaxy Lensing: A Promising Union to Constrain Cosmological Parameters

    OpenAIRE

    Cacciato, Marcello; Bosch, Frank C. van den; More, Surhud; Li, Ran; Mo, H. J.; Yang, Xiaohu

    2008-01-01

    Galaxy clustering and galaxy-galaxy lensing probe the connection between galaxies and their dark matter haloes in complementary ways. On one hand, the halo occupation statistics inferred from the observed clustering properties of galaxies are degenerate with the adopted cosmology. Consequently, different cosmologies imply different mass-to-light ratios for dark matter haloes. On the other hand, galaxy-galaxy lensing yields direct constraints on the actual mass-to-light ratios and it can be us...

  2. The Atacama Cosmology Telescope: ACT-CL J0102-4215 "El Gordo," a Massive Merging Cluster at Redshift 0.87

    Science.gov (United States)

    Menanteau, Felipe; Hughes, John Pl; Baker, Andrew J.; Sifon, Cristobal; Gonzalez, Jorge; Infante, Leopoldo; Barrientos, L. Felipe; Hilton, Matt; Das, Sudeep; Spergel, David N.; Hincks, Adam D.; Page, Lyman A.; Staggs, Suzanne T.; Mardsen, Danica; Reese, Erik D.; Dunkley, Joanna; Kosowsky, Arthur; Marriage, Tobias A.; Moodley, Kavilan; Niemack, Michael D.; Sehgal, Neelima; Sievers, Jon

    2011-01-01

    We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant Sunyaev-Zeldovich (SZ) decrement in a sky survey area of 755 square degrees. Our VLT/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, sigma(gal) +/- 1321 106 km s-1. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T(X) = 14:5 +/- 0:1 keV and 0.5 2.0 keV band luminosity of L(X) = (2:19 0:11) 1045 h(exp -2)70erg s-1. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y(X) , and integrated SZ distortion, we estimate a cluster mass of M(200) = (2:16 +/- 0:32) 10(exp 15) h(exp-1) 70M compared to the Sun. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6:6 +/- 0:7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 +/- 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other from which we estimate a merger speed of around 1300 km s(exp -1) for an assumed merger timescale of 1 Gyr. ACTCL J0102-4915 is possibly a high-redshift analog of the famous Bullet Cluster. Such a massive cluster at this redshift is rare, although consistent with the standard CDM cosmology in the lower part of its allowed mass range. Massive

  3. Chandra X-ray Observatory Study of the Orion Nebula Cluster and BN/KL Region

    OpenAIRE

    Garmire, Gordon,; Feigelson, Eric D.; Broos, Patrick; Hillenbrand, Lynne A.; Pravdo, Steven H.; Townsley, Leisa; Tsuboi, Yohko

    2000-01-01

    About 1000 X-ray emitting young pre-main sequence (PMS) stars distributed in mass from 0.05 to 50 solar masses are detected in an image of the Orion Nebula obtained with the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory. This is the richest field of sources ever obtained in X-ray astronomy. ACIS sources include 85-90% of V

  4. The relation between gas density and velocity power spectra in galaxy clusters: qualitative treatment and cosmological simulations

    CERN Document Server

    Zhuravleva, I; Schekochihin, A A; Lau, E T; Nagai, D; Gaspari, M; Allen, S W; Nelson, K; Parrish, I J

    2014-01-01

    We address the problem of evaluating the power spectrum of the velocity field of the ICM using only information on the plasma density fluctuations, which can be measured today by Chandra and XMM-Newton observatories. We argue that for relaxed clusters there is a linear relation between the rms density and velocity fluctuations across a range of scales, from the largest ones, where motions are dominated by buoyancy, down to small, turbulent scales: $(\\delta\\rho_k/\\rho)^2 = \\eta_1^2 (V_{1,k}/c_s)^2$, where $\\delta\\rho_k/\\rho$ is the spectral amplitude of the density perturbations at wave number $k$, $V_{1,k}^2=V_k^2/3$ is the mean square component of the velocity field, $c_s$ is the sound speed, and $\\eta_1$ is a dimensionless constant of order unity. Using cosmological simulations of relaxed galaxy clusters, we calibrate this relation and find $\\eta_1\\approx 1 \\pm 0.3$. We argue that this value is set at large scales by buoyancy physics, while at small scales the density and velocity power spectra are proporti...

  5. A Chandra X-ray study of the interacting binaries in the old open cluster NGC6791

    CERN Document Server

    Berg, Maureen van den; Tagliaferri, Gianpiero; Belloni, Tomaso; Bedin, Luigi R; Platais, Imants

    2013-01-01

    We present the first X-ray study of NGC6791, one of the oldest open clusters known (8 Gyr). Our Chandra observation is aimed at uncovering the population of close interacting binaries down to Lx ~ 1e30 erg/s (0.3-7 keV). We detect 86 sources within 8 arcmin of the cluster center, including 59 inside the half-mass radius. We identify twenty sources with proper-motion cluster members, which are a mix of cataclysmic variables (CVs), active binaries (ABs), and binaries containing sub-subgiants. With follow-up optical spectroscopy we confirm the nature of one CV. We discover one new, X-ray variable candidate CV with Balmer and HeII emission lines in its optical spectrum; this is the first X-ray--selected CV confirmed in an open cluster. The number of CVs per unit mass is consistent with the field, suggesting that the 3-4 CVs observed in NGC6791 are primordial. We compare the X-ray properties of NGC6791 with those of a few old open (NGC6819, M67) and globular clusters (47Tuc, NGC6397). It is puzzling that the numbe...

  6. Chandra Measurements of a Complete Sample of X-ray Luminous Galaxy Clusters: The Luminosity-Mass Relation

    CERN Document Server

    Giles, P A; Dahle, H; Bonamente, M; Landry, D; Jones, C; Joy, M; Murray, S S; van der Pyl, N

    2015-01-01

    We present the results of work involving a statistically complete sample of 34 galaxy clusters, in the redshift range 0.15$\\le$z$\\le$0.3 observed with Chandra. We present the calibration of the Mass-Temperature (MT) relation using hydrostatic mass estimates for the most dynamically relaxed clusters, and use this relation as a mass proxy for the full cluster sample. We find that the slope of the MT relation follows the self-similar expectation, and is consistent with previously published relations. We investigate the luminosity-Mass (LM) relation for the cluster sample, utilising a method to fully account for selection biases. We find that the difference in normalisation of the LM relation with and without accounting for selection effects is $\\approx$2. For a cluster of luminosity 10$^{45}$ erg s$^{-1}$, we find that the mass estimated from the LM relation when we account for selection effects is $\\approx$40% higher compared to the sample LM relation (not accounting for selection effects).

  7. A CHANDRA X-RAY STUDY OF THE INTERACTING BINARIES IN THE OLD OPEN CLUSTER NGC 6791

    Energy Technology Data Exchange (ETDEWEB)

    Van den Berg, Maureen [Astronomical Institute ' ' Anton Pannekoek' ' , University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Verbunt, Frank [Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen (Netherlands); Tagliaferri, Gianpiero; Belloni, Tomaso [INAF/Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (Italy); Bedin, Luigi R. [INAF/Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Platais, Imants, E-mail: M.C.vandenBerg@uva.nl [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

    2013-06-20

    We present the first X-ray study of NGC 6791, one of the oldest open clusters known (8 Gyr). Our Chandra observation is aimed at uncovering the population of close interacting binaries down to L{sub X} Almost-Equal-To 1 Multiplication-Sign 10{sup 30} erg s{sup -1} (0.3-7 keV). We detect 86 sources within 8' of the cluster center, including 59 inside the half-mass radius. We identify 20 sources with proper-motion cluster members, which are a mix of cataclysmic variables (CVs), active binaries (ABs), and binaries containing sub-subgiants. With follow-up optical spectroscopy, we confirm the nature of one CV. We discover one new, X-ray variable candidate CV with Balmer and He II emission lines in its optical spectrum; this is the first X-ray-selected CV in an open cluster. The number of CVs per unit mass is consistent with the field, suggesting that the 3-4 CVs observed in NGC 6791 are primordial. We compare the X-ray properties of NGC 6791 with those of a few old open (NGC 6819, M 67) and globular clusters (47 Tuc, NGC 6397). It is puzzling that the number of ABs brighter than 1 Multiplication-Sign 10{sup 30} erg s{sup -1} normalized by cluster mass is lower in NGC 6791 than in M 67 by a factor {approx}3-7. CVs, ABs, and sub-subgiants brighter than 1 Multiplication-Sign 10{sup 30} erg s{sup -1} are under-represented per unit mass in the globular clusters compared to the oldest open clusters, and this accounts for the lower total X-ray luminosity per unit mass of the former. This indicates that the net effect of dynamical encounters may be the destruction of even some of the hardest (i.e., X-ray-emitting) binaries.

  8. THE ATACAMA COSMOLOGY TELESCOPE: PHYSICAL PROPERTIES OF SUNYAEV-ZEL'DOVICH EFFECT CLUSTERS ON THE CELESTIAL EQUATOR {sup ,}

    Energy Technology Data Exchange (ETDEWEB)

    Menanteau, Felipe; Hughes, John P. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Sifon, Cristobal; Barrientos, L. Felipe; Duenner, Rolando; Infante, Leopoldo [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Battaglia, Nicholas [McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Bond, J. Richard; Hajian, Amir; Hincks, Adam D. [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Crichton, Devin; Gralla, Megan; Marriage, Tobias A. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218-2686 (United States); Das, Sudeep [High Energy Physics Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, IL 60439 (United States); Devlin, Mark J.; Dicker, Simon [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Hasselfield, Matthew [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Hilton, Matt [Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Durban (South Africa); Kosowsky, Arthur [Physics and Astronomy Department, University of Pittsburgh, 100 Allen Hall, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); Marsden, Danica [Department of Physics, University of California Santa Barbara, CA 93106 (United States); and others

    2013-03-01

    We present the optical and X-ray properties of 68 galaxy clusters selected via the Sunyaev-Zel'dovich (SZ) effect at 148 GHz by the Atacama Cosmology Telescope (ACT). Our sample, from an area of 504 deg{sup 2} centered on the celestial equator, is divided into two regions. The main region uses 270 deg{sup 2} of the ACT survey that overlaps with the co-added ugriz imaging from the Sloan Digital Sky Survey (SDSS) over Stripe 82 plus additional near-infrared pointed observations with the Apache Point Observatory 3.5 m telescope. We confirm a total of 49 clusters to z Almost-Equal-To 1.3, of which 22 (all at z > 0.55) are new discoveries. For the second region, the regular-depth SDSS imaging allows us to confirm 19 more clusters up to z Almost-Equal-To 0.7, of which 10 systems are new. We present the optical richness, photometric redshifts, and separation between the SZ position and the brightest cluster galaxy (BCG). We find no significant offset between the cluster SZ centroid and BCG location and a weak correlation between optical richness and SZ-derived mass. We also present X-ray fluxes and luminosities from the ROSAT All Sky Survey which confirm that this is a massive sample. One of the newly discovered clusters, ACT-CL J0044.4+0113 at z = 1.1 (photometric), has an integrated XMM-Newton X-ray temperature of kT{sub X} = 7.9 {+-} 1.0 keV and combined mass of M {sub 200a} = 8.2{sup +3.3} {sub -2.5} Multiplication-Sign 10{sup 14} h {sup -1} {sub 70} M {sub Sun }, placing it among the most massive and X-ray-hot clusters known at redshifts beyond z = 1. We also highlight the optically rich cluster ACT-CL J2327.4-0204 (RCS2 2327) at z = 0.705 (spectroscopic) as the most significant detection of the whole equatorial sample with a Chandra-derived mass of M {sub 200a} = 1.9{sup +0.6} {sub -0.4} Multiplication-Sign 10{sup 15} h {sup -1} {sub 70} M {sub Sun }, placing it in the ranks of the most massive known clusters like El Gordo and the Bullet Cluster.

  9. Chandra X-Ray Spectral Analysis of Cooling Flow Clusters, 2A 0335+096 and Abell 2199

    CERN Document Server

    Kawano, N; Fukazawa, Y; Kawano, Naomi; Ohto, Akimitsu; Fukazawa, Yasushi

    2003-01-01

    We report on a spatially resolved analysis of Chandra X-ray data on a nearby typical cooling flow cluster of galaxies 2A 0335+096, together with A 2199 for a comparison. As recently found in the cores of other clusters, the temperature around the central part of 2A 0335+096 is 1.3--1.5 keV, which is higher than that inferred from the cooling flow picture. Furthermore, the absorption column density is almost constant against the radius in 2A 0335+096; there is no evidence of excess absorption up to 200--250 kpc. This indicates that no significant amount of cold material, which has cooled down, is present. These properties are similar to those of A 2199. Since the cooling time in the central part is much shorter than the age of the clusters, a heating mechanism, which weakens the effect of radiative cooling, is expected to be present in the central part of both clusters of galaxies. Both 2A 0335+096 and A 2199 have radio jets associated with their cD galaxy. We discuss the possibility of heating processes cause...

  10. Chandra X-ray Observations of the Young Stellar Cluster NGC 6193 in the Ara OB1 Association

    CERN Document Server

    Skinner, S L; Palla, F; Barbosa, C L D R

    2005-01-01

    A 90 ks Chandra HETG observation of the young stellar cluster NGC 6193 in the southern Ara OB1 association detected 43 X-ray sources in a 2' x 2' core region centered on the young O stars HD 150135 (O6.5V) and HD 150136 (O3+O6V). The cluster is dominated by exceptionally bright X-ray emission from the two O stars, which are separated by only 10 arcsecs. The X-ray luminosity of HD 150136 is log Lx = 33.39 (ergs/s), making it one of the most luminous O-star X-ray sources known. All of the fainter X-ray sources in the core region have near-IR counterparts, but JHK photometry provides little evidence for near-IR excesses. These core sources have typical mean photon energies of 2 keV and about one-third are variable. It is likely that some are young low-mass stars in the cluster, but cluster membership remains to be determined. Grating spectra show that the X-ray properties of HD 150135 and HD 150136 are similar, but not identical. Both have moderately broadened unshifted emission lines and their emission is domin...

  11. Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses

    Science.gov (United States)

    Caldwell, C. E.; McCarthy, I. G.; Baldry, I. K.; Collins, C. A.; Schaye, J.; Bird, S.

    2016-11-01

    The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary cosmic microwave background (CMB) data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is required to convert the standard theoretical prediction (the halo mass function) into counts as a function of the observable (e.g. X-ray luminosity, Sunyaev-Zel'dovich flux, and optical richness). Here we propose an alternative strategy, which is to directly compare predicted and observed cluster counts as a function of the one-dimensional velocity dispersion of the cluster galaxies. We argue that the velocity dispersion of groups/clusters can be theoretically predicted as robustly as mass but, unlike mass, it can also be directly observed, thus circumventing the main systematic bias in traditional cluster counts studies. With the aid of the BAHAMAS suite of cosmological hydrodynamical simulations, we demonstrate the potential of the velocity dispersion counts for discriminating even similar Λ cold dark matter models. These predictions can be compared with the results from existing redshift surveys such as the highly complete Galaxy And Mass Assembly survey, and upcoming wide-field spectroscopic surveys such as the Wide Area Vista Extragalactic Survey and the Dark Energy Survey Instrument.

  12. Chandra observation of the cluster environment of a WAT radio source in Abell 1446

    NARCIS (Netherlands)

    E.M. Douglass; E.L. Blanton; T.E. Clarke; C.L. Sarazin; M. Wise

    2008-01-01

    Wide-angle tail (WAT) radio sources are often found in the centers of galaxy clusters where intracluster medium (ICM) ram pressure may bend the lobes into their characteristic C-shape. We examine the low-redshift (z = 0.1035) cluster Abell 1446, host to the WAT radio source 1159+583. The cluster exh

  13. Cosmology

    International Nuclear Information System (INIS)

    An extensive first part on a wealth of observational results relevant to cosmology lays the foundation for the second and central part of the book; the chapters on general relativity, the various cosmological theories, and the early universe. The authors present in a complete and almost non-mathematical way the ideas and theoretical concepts of modern cosmology including the exciting impact of high-energy particle physics, e.g. in the concept of the ''inflationary universe''. The final part addresses the deeper implications of cosmology, the arrow of time, the universality of physical laws, inflation and causality, and the anthropic principle

  14. Cosmology

    CERN Document Server

    Rubakov, V A

    2014-01-01

    In these lectures we first concentrate on the cosmological problems which, hopefully, have to do with the new physics to be probed at the LHC: the nature and origin of dark matter and generation of matter-antimatter asymmetry. We give several examples showing the LHC cosmological potential. These are WIMPs as cold dark matter, gravitinos as warm dark matter, and electroweak baryogenesis as a mechanism for generating matter-antimatter asymmetry. In the remaining part of the lectures we discuss the cosmological perturbations as a tool for studying the epoch preceeding the conventional hot stage of the cosmological evolution.

  15. Simultaneous Constraints on Cosmology and Photometric Redshift Bias from Weak Lensing and Galaxy Clustering

    CERN Document Server

    Samuroff, S; Bridle, SL; Zuntz, J; MacCrann, N; Krause, E; Eifler, T; Kirk, D

    2016-01-01

    We investigate the expected cosmological constraints from a combination of weak lensing and large-scale galaxy clustering using realistic redshift distributions. Introducing a systematic bias in the weak lensing redshift distributions (of 0.05 in redshift) produces a $>2\\sigma$ bias in the recovered matter power spectrum amplitude and dark energy equation of state, for preliminary Stage III surveys. We demonstrate that these cosmological errors can be largely removed by marginalising over unknown biases in the assumed weak lensing redshift distributions, if we assume high quality redshift information for the galaxy clustering sample. Furthermore the cosmological constraining power is mostly retained despite removing much of the information on the weak lensing redshift distribution biases. We show that this comes from complementary degeneracy directions between cosmic shear and the combination of galaxy clustering with cross-correlation between shear and galaxy number density. Finally we examine how the self-c...

  16. Deep Chandra observation of the galaxy cluster WARPJ1415.1+3612 at z=1: an evolved cool-core cluster at high-redshift

    CERN Document Server

    Santos, Joana S; Rosati, Piero; Nonino, Mario; Giovannini, Gabriele

    2011-01-01

    Using the deepest (370 ksec) Chandra observation of a high-redshift galaxy cluster, we perform a detailed characterization of the intra-cluster medium (ICM) of WARPJ1415.1+3612 at z=1.03. We also explore the connection between the ICM core properties and the radio/optical properties of the brightest cluster galaxy (BCG). We perform a spatially resolved analysis of the ICM to obtain temperature, metallicity and surface brightness profiles. Using the deprojected temperature and density profiles we accurately derive the cluster mass at different overdensities. In addition to the X-ray data, we use archival radio VLA imaging and optical GMOS spectroscopy of the central galaxy to investigate the feedback between the central galaxy and the ICM. The X-ray spectral analysis shows a significant temperature drop towards the cluster center, with a projected value of Tc = 4.6 \\pm 0.4 keV, and a remarkably high central iron abundance peak, Zc= 3.6 Zsun. The central cooling time is shorter than 0.1 Gyr and the entropy is e...

  17. Planck 2015 results. XXIV. Cosmology from Sunyaev-Zeldovich cluster counts

    CERN Document Server

    Ade, P A R; Arnaud, M; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartlett, J G; Bartolo, N; Battaner, E; Battye, R; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Challinor, A; Chamballu, A; Chary, R -R; Chiang, H C; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Comis, B; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Désert, F -X; Diego, J M; Dolag, K; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Falgarone, E; Fergusson, J; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Giard, M; Giraud-Héraud, Y; Gjerløw, E; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Hansen, F K; Hanson, D; Harrison, D L; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Kneissl, R; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Lesgourgues, J; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maggio, G; Maino, D; Mandolesi, N; Mangilli, A; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; McGehee, P; Meinhold, P R; Melchiorri, A; Melin, J -B; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Partridge, B; Pasian, F; Patanchon, G; Pearson, T J; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rachen, J P; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Roman, M; Rosset, C; Rossetti, M; Roudier, G; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Seiffert, M D; Shellard, E P S; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Türler, M; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; Weller, J; White, S D M; Yvon, D; Zacchei, A; Zonca, A

    2015-01-01

    We present cluster counts and corresponding cosmological constraints from the Planck full mission data set. Our catalogue consists of 439 clusters detected via their Sunyaev-Zeldovich (SZ) signal down to a signal-to-noise of six, and is more than a factor of two larger than the 2013 Planck cluster cosmology sample. The counts are consistent with those from 2013 and yield compatible constraints under the same modelling assumptions. Taking advantage of the larger catalogue, we extend our analysis to the two-dimensional distribution in redshift and signal-to-noise. We use mass estimates from two recent studies of gravitational lensing of background galaxies by Planck clusters to provide priors on the hydrostatic bias parameter, $1-b$. In addition, we use lensing of cosmic microwave background (CMB) temperature fluctuations by Planck clusters as a third independent constraint on this parameter. These various calibrations imply constraints on the present-day amplitude of matter fluctuations in varying degrees of t...

  18. Probing cosmology with weak lensing selected clusters II: Dark energy and f(R) gravity models

    CERN Document Server

    Shirasaki, Masato; Yoshida, Naoki

    2015-01-01

    Ongoing and future wide-field galaxy surveys can be used to locate a number of clusters of galaxies with cosmic shear measurement alone. We study constraints on cosmological models using statistics of weak lensing selected galaxy clusters. We extend our previous theoretical framework to model the statistical properties of clusters in variants of cosmological models as well as in the standard LCDM model. Weak lensing selection of clusters does not rely on the conventional assumption such as the relation between luminosity and mass and/or hydrostatic equilibrium, but a number of observational effects compromise robust identification. We use a large set of realistic mock weak-lensing catalogs as well as analytic models to perform a Fisher analysis and make forecast for constraining two competing cosmological models, wCDM model and f(R) model proposed by Hu & Sawicki, with our lensing statistics. We show that weak lensing selected clusters are excellent probe of cosmology when combined with cosmic shear power...

  19. Cosmological parameter estimation from CMB and X-ray clusters after Planck

    CERN Document Server

    Hu, Jian-Wei; Guo, Zong-Kuan; Hu, Bin

    2014-01-01

    We update the cosmological parameter estimation for three non-vanilla models by a joint analysis of \\CCCP\\ X-ray cluster, the newly released \\Planck\\ CMB data as well as some external data sets, such as baryon acoustic oscillation measurements from the 6dFGS, SDSS DR7 and BOSS DR9 surveys, and Hubble Space Telescope $H_0$ measurement. First of all, we find that X-ray cluster data sets strongly favor a non-zero summed neutrino mass at more than 3$\\sigma$ confidence level in these non-vanilla models. And then, we reveal some tensions between X-ray cluster and {\\it Planck} data in some cosmological parameters. For the matter power spectrum amplitude $\\sigma_8$, X-ray cluster data favor a lower value compared with {\\it Planck}. Because of the strong $\\sigma_8-\\sum m_{\

  20. 7.1 keV sterile neutrino constraints from X-ray observations of 33 clusters of galaxies with Chandra ACIS

    OpenAIRE

    Hofmann, F.; Sanders, J. S.; Nandra, K.; Clerc, N; De Gaspari, M.

    2016-01-01

    Recently an unidentified emission line at 3.55 keV has been detected in X-ray spectra of clusters of galaxies. The line has been discussed as a possible decay signature of 7.1 keV sterile neutrinos, which have been proposed as a dark matter candidate. We aim at putting constraints on the proposed line emission in a large sample of Chandra-observed clusters and obtain limits on the mixing-angle in a 7.1 keV sterile neutrino dark matter scenario. For a sample of 33 high-mass clusters of galaxie...

  1. Cluster Structure in Cosmological Simulations I: Correlation to Observables, Mass Estimates, and Evolution

    OpenAIRE

    Jeltema, Tesla E.; Hallman, Eric J.; Burns, Jack O.; Motl, Patrick M

    2007-01-01

    We use Enzo, a hybrid Eulerian AMR/N-body code including non-gravitational heating and cooling, to explore the morphology of the X-ray gas in clusters of galaxies and its evolution in current generation cosmological simulations. We employ and compare two observationally motivated structure measures: power ratios and centroid shift. Overall, the structure of our simulated clusters compares remarkably well to low-redshift observations, although some differences remain that may point to incomple...

  2. The formation of the brightest cluster galaxies in cosmological simulations: the case for AGN feedback

    OpenAIRE

    Martizzi, Davide; Teyssier, Romain; Moore, Ben

    2011-01-01

    We use 500 pc resolution cosmological simulations of a Virgo-like galaxy cluster to study the properties of the brightest cluster galaxy (BCG) that forms at the center of the halo. We compared two simulations; one incorporating only supernovae feedback and a second that also includes prescriptions for black hole growth and the resulting AGN feedback from gas accretion. As previous work has shown, with supernovae feedback alone we are unable to reproduce any of the observed properties of massi...

  3. Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts

    DEFF Research Database (Denmark)

    Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.;

    2013-01-01

    We present constraints on cosmological parameters using number counts as a function of redshift for a sub-sample of 189 galaxy clusters from the Planck SZ (PSZ) catalogue. The PSZ is selected through the signature of the Sunyaev-Zeldovich (SZ) effect, and the sub-sample used here has a signal-to-...

  4. Ten Years of Chandra

    Science.gov (United States)

    Weisskopf, Martin C.

    2009-01-01

    We celebrated the 10-th anniversary of the Launch of the Chandra X-ray Observatory on July 13, 2009. During these 10 years data from this Great Observatory have had a profound impact on 21st century astrophysics. With its unrivaled capability to produce sub-arcsecond images, the Observatory has enabled astronomers to make new discoveries in topics as diverse as comets and cosmology. We shall review some of the highlights, discuss the current status, and future plans.

  5. Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses

    CERN Document Server

    Caldwell, C E; Baldry, I K; Collins, C A; Schaye, J; Bird, S

    2016-01-01

    The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary CMB data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is required to convert the standard theoretical prediction (the halo mass function) into counts as a function of the observable (e.g., X-ray luminosity, Sunyaev-Zel'dovich flux, optical richness). Here we propose an alternative strategy, which is to directly compare predicted and observed cluster counts as a function of the one-dimensional velocity dispersion of the cluster galaxies. We argue that the velocity dispersion of groups/clusters can be theoretically predicted as robustly as mass but, unlike mass, it can also be directly observed, ...

  6. Joint Analysis of Cluster Observations: II. Chandra/XMM-Newton X-ray and Weak Lensing Scaling Relations for a Sample of 50 Rich Clusters of Galaxies

    CERN Document Server

    Mahdavi, A; Babul, A; Bildfell, C; Jeltema, T; Henry, J P

    2012-01-01

    We present a study of multiwavelength X-ray and weak lensing scaling relations for a sample of 50 clusters of galaxies. Our analysis combines Chandra and XMM-Newton data using an energy-dependent cross-calibration. After considering a number of scaling relations, we find that gas mass is the most robust estimator of weak lensing mass, yielding 15 +/- 6% intrinsic scatter at r500. The scatter does not change when measured within a fixed physical radius of 1 Mpc. Clusters with small BCG to X-ray peak offsets constitute a very regular population whose members have the same gas mass fractions and whose even smaller <10% deviations from regularity can be ascribed to line of sight geometrical effects alone. Cool-core clusters, while a somewhat different population, also show the same (<10%) scatter in the gas mass-lensing mass relation. There is a good correlation and a hint of bimodality in the plane defined by BCG offset and central entropy (or central cooling time). The pseudo-pressure YX does not discrimi...

  7. A deep Chandra observation of the poor cluster AWM4 - II. The role of the radio jets in enriching the intra-cluster medium

    CERN Document Server

    O'Sullivan, Ewan; David, Laurence P; Vrtilek, Jan M; Raychaudhury, Somak

    2010-01-01

    We use a Chandra observation of the poor cluster AWM4 to map the temperature and abundance of the intra-cluster medium, so as to examine the influence of the central radio galaxy on its environment. While the cluster core is generally enriched to near-solar abundances, we find evidence of super-solar abundances correlated with the radio jets, extending ~35 kpc from the core of the central dominant galaxy NGC 6051 along its minor axis. We conclude that the enriched gas has been transported out of the central galaxy through the action of the radio source. We estimate the excess mass of iron in the entrained gas to be ~1.4x10^6 Msol, and find that this can be produced in the core of NGC 6051 within the timescale of the AGN outburst. The energy required to transport this gas to its current location is ~4.5x10^57 erg, a significant fraction of the estimated total mechanical energy output of the AGN, though this estimate is dependent on the degree of enrichment of the uplifted gas. The larger near-solar abundance r...

  8. Probing cosmology and galaxy cluster structure with the Sunyaev-Zel'dovich decrement versus X-ray temperature scaling relation

    OpenAIRE

    Shang, Cien; Haiman, Zoltan; Verde, Licia

    2009-01-01

    Scaling relations among galaxy cluster observables, which will become available in large future samples of galaxy clusters, could be used to constrain not only cluster structure, but also cosmology. We study the utility of this approach, employing a physically motivated parametric model to describe cluster structure, and applying it to the expected relation between the Sunyaev-Zel'dovich decrement (S_\

  9. The Atacama Cosmology Telescope: Physical Properties and Purity of a Galaxy Cluster Sample Selected via the Sunyaev-Zel'dovich Effect

    CERN Document Server

    Menanteau, Felipe; Juin, Jean-Baptiste; Marriage, Tobias A; Reese, Erik; Acquaviva, Viviana; Aguirre, Paula; Appel, John William; Baker, Andrew J; Barrientos, L Felipe; Battistelli, Elia S; Bond, J Richard; Das, Sudeep; Devlin, Mark J; Dicker, Simon; Deshpande, Amruta J; Dunkley, Joanna; Dunner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph W; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hernandez-Monteagudo, Carlos; Hilton, Matt; Hincks, Adam D; Hlozek, Renee; Hughes, John P; Huffenberger, Kevin M; Infante, Leopoldo; Irwin, Kent D; Klein, Jeff; Kosowsky, Arthur; Lin, Yen-Ting; Marsden, Danica; Moodley, Kavilan; Niemack, Michael D; Nolta, Michael R; Page, Lyman A; Parker, Lucas; Partridge, Bruce; Sievers, Jon; Sehgal, Neelima; Spergel, David N; Staggs, Suzanne T; Swetz, Daniel; Switzer, Eric; Thornton, Robert; Trac, Hy; Warne, Ryan; Wollack, Ed

    2010-01-01

    We present optical and X-ray properties for the first confirmed galaxy cluster sample selected by the Sunyaev-Zel'dovich Effect from 148 GHz maps over 455 square degrees of sky made with the Atacama Cosmology Telescope. These maps, coupled with multi-band imaging on 4-meter-class optical telescopes, have yielded a sample of 23 galaxy clusters with redshifts between 0.118 and 1.066. Of these 23 clusters, 10 are newly discovered. The selection of this sample is approximately mass limited and essentially independent of redshift. We provide optical positions, images, redshifts and X-ray fluxes and luminosities for the full sample, and X-ray temperatures of an important subset. The mass limit of the full sample is around 8e14 Msun, with a number distribution that peaks around a redshift of 0.4. For the 10 highest significance SZE-selected cluster candidates, all of which are optically confirmed, the mass threshold is 1e15 Msun and the redshift range is 0.167 to 1.066. Archival observations from Chandra, XMM-Newton...

  10. Galaxy Cluster Scaling Relations between Bolocam Sunyaev-Zel'dovich Effect and Chandra X-ray Measurements

    CERN Document Server

    Czakon, N G; Mantz, A; Golwala, S R; Downes, T P; Koch, P M; Lin, K -Y; Molnar, S M; Moustakas, L A; Mroczkowski, T; Pierpaoli, E; Shitanishi, J A; Siegel, S; Umetsu, K

    2014-01-01

    We present scaling relations between the integrated Sunyaev-Zel'dovich Effect (SZE) signal, $Y_{\\rm SZ}$, its X-ray analogue, $Y_{\\rm X}$$\\equiv$$M_{\\rm gas}$$T_{\\rm X}$, and total mass, $M_{\\rm tot}$, for the 45 galaxy clusters in the Bolocam X-ray-SZ (BOXSZ) sample. All parameters are integrated within $r_{2500}$. $Y_{2500}$ values are measured using SZE data collected with Bolocam, operating at 140 GHz at the Caltech Submillimeter Observatory (CSO). The temperature, $T_{\\rm X}$, and mass, $M_{\\rm gas,2500}$, of the intracluster medium are determined using X-ray data collected with \\emph{Chandra}, and $M_{\\rm tot}$ is derived from $M_{\\rm gas}$ using a constant gas mass fraction. Our analysis accounts for several potential sources of bias, including: selection effects, contamination from radio point sources, and the loss of SZE signal due to noise filtering and beam-smoothing effects. We measure the $Y_{2500}$-$Y_{\\rm X}$ scaling to have a logarithmic slope of $0.84\\pm0.07$, and a fractional intrinsic scatt...

  11. THE ATACAMA COSMOLOGY TELESCOPE: ACT-CL J0102-4915 'EL GORDO', A MASSIVE MERGING CLUSTER AT REDSHIFT 0.87

    Energy Technology Data Exchange (ETDEWEB)

    Menanteau, Felipe; Hughes, John P.; Baker, Andrew J. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Rd, Piscataway, NJ 08854 (United States); Sifon, Cristobal; Gonzalez, Jorge; Infante, Leopoldo; Felipe Barrientos, L. [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Hilton, Matt [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Bond, John R.; Hajian, Amir; Nolta, Michael R. [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Das, Sudeep [Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States); Devlin, Mark J.; Marsden, Danica [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Dunkley, Joanna [Department of Astrophysics, Oxford University, Oxford, OX1 3RH (United Kingdom); Hincks, Adam D. [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); Kosowsky, Arthur [Physics and Astronomy Department, University of Pittsburgh, 100 Allen Hall, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); Marriage, Tobias A. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218-2686 (United States); Moodley, Kavilan [Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban 4041 (South Africa); Niemack, Michael D. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); and others

    2012-03-20

    We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant SZ decrement in a sky survey area of 755 deg{sup 2}. Our Very Large Telescope (VLT)/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, {sigma}{sub gal} = 1321 {+-} 106 km s{sup -1}. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T{sub X} = 14.5 {+-} 0.1 keV and 0.5-2.0 keV band luminosity of L{sub X} = (2.19 {+-} 0.11) Multiplication-Sign 10{sup 45} h{sup -2}{sub 70} erg s{sup -1}. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y{sub X}, and integrated SZ distortion, we estimate a cluster mass of M{sub 200a} = (2.16 {+-} 0.32) Multiplication-Sign 10{sup 15} h{sup -1}{sub 70} M{sub Sun }. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6 {+-} 0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 {+-} 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102-4915 is possibly a high

  12. The Atacama Cosmology Telescope: ACT-CL J0102-4915 'EL GORDO', A Massive Merging Cluster at Redshift 0.87

    Science.gov (United States)

    Menanteau, Felipe; Hughes, John P.; Sifon, Cristobal; Hilton, Matt; Gonzalez, Jorge; Infante, Leopoldo; Barrientos, L. Felipe; Baker, Andrew J.; Bond, John R.; Das, Sudeep; Devlin, Mark J.; Dunkley, Joanna; Hajian, Amir; Hincks, Adam D.; Kosowsky, Arthur; Marsden, Danica; Marriage, Tobias A.; Moodley, Kavilan; Niemack, Michael D.; Nolta, Michael R.; Page, Lyman A.; Reese, Erik D.; Sehgal, Neelima; Seivers, Jon; Spergel, David N.; Staggs, Suzanne T.; Wollack, Edward

    2012-01-01

    We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant Sunyaev-Zeldovich (SZ) decrement in a sky survey area of 755 square degrees. Our VLT/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, sigma(sub gal) = 1321+/-106 km s-1. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T(sub X) = 14.5+/-1.0 keV and 0.5-2.0 keV band luminosity of L(sub X) = (2.19+/-0.11)×10(sup 45) h(sup -2)(sub 70) erg s-1. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y(sub X), and integrated SZ distortion, we estimate a cluster mass of M(sub 200a) = (2.16+/-0.32)×1015 h(sup -1)(sub 70) solar mass. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6+/-0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22+/-6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102-4915 is possibly a high-redshift analog of the famous Bullet Cluster. Such a massive cluster at this redshift

  13. Resolving Globular Cluster Formation within a Cosmological Context

    CERN Document Server

    Boley, Aaron C; Read, Justin; Teyssier, Romain

    2009-01-01

    We place constraints on the formation redshifts for blue globular clusters (BGCs), independent of the details of hydrodynamics and population III star formation. We argue that BGCs and stellar halos have a common origin and that simulations of 1 Mpc boxes up to $z\\sim10$ must resolve BGC formation. We present a proof-of-concept simulation that captures the formation of globular-like star clusters.

  14. Cosmological constraints from Subaru weak lensing cluster counts

    CERN Document Server

    Hamana, Takashi; Koike, Michitaro; Miller, Lance

    2015-01-01

    We present results of weak lensing cluster counts obtained from 11 sq.deg SuprimeCam data. Although the area is much smaller than previous work dealing with weak lensing peak statistics, the number density of galaxies usable for weak lensing analysis is about twice as large as those. The higher galaxy number density reduces the noise in the weak lensing mass maps, and thus increases the signal-to-noise ratio of peaks of the lensing signal due to massive clusters. This enables us to construct a weak lensing selected cluster sample by adopting a high threshold S/N, such that the contamination rate due to false signals is small. We find 6 peaks with S/N>5. For all the peaks, previously identified clusters of galaxies are matched within a separation of 1 arcmin, demonstrating good correspondence between the peaks and clusters of galaxies. We evaluate the statistical error using mock weak lensing data, and find Npeak=6+/-3.1 in an effective area of 9.0 sq.deg. We compare the measured weak lensing cluster counts wi...

  15. Cosmological constraints from Sunyaev-Zeldovich cluster counts: an approach to account for missing redshifts

    CERN Document Server

    Bonaldi, A; Brown, M L

    2014-01-01

    The accumulation of redshifts provides a significant observational bottleneck when using galaxy cluster surveys to constrain cosmological parameters. We propose a simple method to allow the use of samples where there is a fraction of the redshifts that are not known. The simplest assumption is that the missing redshifts are randomly extracted from the catalogue, but the method also allows one to take into account known selection effects in the accumulation of redshifts. We quantify the reduction in statistical precision of cosmological parameter constraints as a function of the fraction of missing redshifts for simulated surveys, and also investigate the impact of making an incorrect assumption for the distribution of missing redshifts.

  16. JOINT ANALYSIS OF CLUSTER OBSERVATIONS. II. CHANDRA/XMM-NEWTON X-RAY AND WEAK LENSING SCALING RELATIONS FOR A SAMPLE OF 50 RICH CLUSTERS OF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Mahdavi, Andisheh [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94131 (United States); Hoekstra, Henk [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden (Netherlands); Babul, Arif; Bildfell, Chris [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada); Jeltema, Tesla [Santa Cruz Institute for Particle Physics, UC Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Henry, J. Patrick [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2013-04-20

    We present a study of multiwavelength X-ray and weak lensing scaling relations for a sample of 50 clusters of galaxies. Our analysis combines Chandra and XMM-Newton data using an energy-dependent cross-calibration. After considering a number of scaling relations, we find that gas mass is the most robust estimator of weak lensing mass, yielding 15% {+-} 6% intrinsic scatter at r{sub 500}{sup WL} (the pseudo-pressure Y{sub X} yields a consistent scatter of 22% {+-} 5%). The scatter does not change when measured within a fixed physical radius of 1 Mpc. Clusters with small brightest cluster galaxy (BCG) to X-ray peak offsets constitute a very regular population whose members have the same gas mass fractions and whose even smaller (<10%) deviations from regularity can be ascribed to line of sight geometrical effects alone. Cool-core clusters, while a somewhat different population, also show the same (<10%) scatter in the gas mass-lensing mass relation. There is a good correlation and a hint of bimodality in the plane defined by BCG offset and central entropy (or central cooling time). The pseudo-pressure Y{sub X} does not discriminate between the more relaxed and less relaxed populations, making it perhaps the more even-handed mass proxy for surveys. Overall, hydrostatic masses underestimate weak lensing masses by 10% on the average at r{sub 500}{sup WL}; but cool-core clusters are consistent with no bias, while non-cool-core clusters have a large and constant 15%-20% bias between r{sub 2500}{sup WL} and r{sub 500}{sup WL}, in agreement with N-body simulations incorporating unthermalized gas. For non-cool-core clusters, the bias correlates well with BCG ellipticity. We also examine centroid shift variance and power ratios to quantify substructure; these quantities do not correlate with residuals in the scaling relations. Individual clusters have for the most part forgotten the source of their departures from self-similarity.

  17. The LABOCA Survey of the Extended Chandra Deep Field South: Clustering of submillimetre galaxies

    CERN Document Server

    Hickox, Ryan C; Smail, Ian; Myers, A D; Alexander, D M; Swinbank, A M; Danielson, A L R; Stott, J P; Chapman, S C; Coppin, K E K; Dunlop, J S; Gawiser, E; Lutz, D; van der Werf, P; Weiss, A

    2011-01-01

    We present a measurement of the spatial clustering of submillimetre galaxies (SMGs) at z = 1-3. Using data from the 870 micron LESS survey, we employ a novel technique to measure the cross-correlation between SMGs and galaxies, accounting for the full probability distributions for photometric redshifts of the galaxies. From the observed projected two-point cross-correlation function we derive the linear bias and characteristic dark matter (DM) halo masses for the SMGs. We detect clustering in the cross-correlation between SMGs and galaxies at the > 4 sigma level. For the SMG autocorrelation we obtain r_0 = 7.7 (+1.8,-2.3) h^-1 Mpc, and derive a corresponding DM halo mass of log(M_halo [h^-1 M_sun]) = 12.8 (+0.3,-0.5). Based on the evolution of DM haloes derived from simulations, we show that that the z = 0 descendants of SMGs are typically massive (~2-3 L*) elliptical galaxies residing in moderate- to high-mass groups (log(M_halo [h^-1 M_sun]) = 13.3 (+0.3,-0.5). From the observed clustering we estimate an SM...

  18. Cluster Structure in Cosmological Simulations. I. Correlation to Observables, Mass Estimates, and Evolution

    Science.gov (United States)

    Jeltema, Tesla E.; Hallman, Eric J.; Burns, Jack O.; Motl, Patrick M.

    2008-07-01

    We use Enzo, a hybrid Eulerian adaptive mesh refinement/N-body code including nongravitational heating and cooling, to explore the morphology of the X-ray gas in clusters of galaxies and its evolution in current-generation cosmological simulations. We employ and compare two observationally motivated structure measures: power ratios and centroid shift. Overall, the structure of our simulated clusters compares remarkably well to low-redshift observations, although some differences remain that may point to incomplete gas physics. We find no dependence on cluster structure in the mass-observable scaling relations, TX-M and YX-M, when using the true cluster masses. However, estimates of the total mass based on the assumption of hydrostatic equilibrium, as assumed in observational studies, are systematically low. We show that the hydrostatic mass bias strongly correlates with cluster structure and, more weakly, with cluster mass. When the hydrostatic masses are used, the mass-observable scaling relations and gas mass fractions depend significantly on cluster morphology, and the true relations are not recovered even if the most relaxed clusters are used. We show that cluster structure, via the power ratios, can be used to effectively correct the hydrostatic mass estimates and mass scaling relations, suggesting that we can calibrate for this systematic effect in cosmological studies. Similar to observational studies, we find that cluster structure, particularly centroid shift, evolves with redshift. This evolution is mild but will lead to additional errors at high redshift. Projection along the line of sight leads to significant uncertainty in the structure of individual clusters: less than 50% of clusters which appear relaxed in projection based on our structure measures are truly relaxed.

  19. Galaxy clusters as probes for cosmology and dark matter

    DEFF Research Database (Denmark)

    Battistelli, Elia S.; Burigana, Carlo; De Bernardis, Paolo;

    2016-01-01

    In recent years, significant progress has been made in building new galaxy clusters samples, at low and high redshifts, from wide-area surveys, particularly exploiting the Sunyaev-Zel'dovich (SZ) effect. A large effort is underway to identify and characterize these new systems with optical/NIR an...

  20. A CHANDRA-VLA INVESTIGATION OF THE X-RAY CAVITY SYSTEM AND RADIO MINI-HALO IN THE GALAXY CLUSTER RBS 797

    Energy Technology Data Exchange (ETDEWEB)

    Doria, Alberto [Argelander-Institut fuer Astronomie, Auf dem Huegel 71, D-53121 Bonn (Germany); Gitti, Myriam; Brighenti, Fabrizio [Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, Bologna 40127 (Italy); Ettori, Stefano [Astronomical Observatory of Bologna-INAF, via Ranzani 1, I-40127 Bologna (Italy); Nulsen, Paul E. J.; McNamara, Brian R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-07-01

    We present a study of the cavity system in the galaxy cluster RBS 797 based on Chandra and Very Large Array (VLA) data. RBS 797 (z = 0.35) is one of the most distant galaxy clusters in which two pronounced X-ray cavities have been discovered. The Chandra data confirm the presence of a cool core and indicate a higher metallicity along the cavity directions. This is likely due to the active galactic nucleus outburst, which lifts cool metal-rich gas from the center along the cavities, as seen in other systems. We find indications that the cavities are hotter than the surrounding gas. Moreover, the new Chandra images show bright rims contrasting with the deep, X-ray deficient cavities. The likely cause is that the expanding 1.4 GHz radio lobes have displaced the gas, compressing it into a shell that appears as bright cool arms. Finally, we show that the large-scale radio emission detected with our VLA observations may be classified as a radio mini-halo, powered by the cooling flow, as it nicely follows the trend P{sub radio} versus P{sub CF} predicted by the reacceleration model.

  1. A Chandra - VLA Investigation of the X-ray Cavity System and Radio Mini-Halo in the Galaxy Cluster RBS 797

    CERN Document Server

    Doria, Alberto; Ettori, Stefano; Brighenti, Fabrizio; Nulsen, Paul E J; McNamara, Brian R

    2012-01-01

    We present a study of the cavity system in the galaxy cluster RBS 797 based on Chandra and VLA data. RBS 797 (z = 0.35), is one of the most distant galaxy clusters in which two pronounced X-ray cavities have been discovered. The Chandra data confirm the presence of a cool core and indicate an higher metallicity along the cavity directions. This is likely due to the AGN outburst, which lifts cool metal-rich gas from the center along the cavities, as seen in other systems. We find indications that the cavities are hotter than the surrounding gas. Moreover, the new Chandra images show bright rims contrasting with the deep, X-ray deficient cavities. The likely cause is that the expanding 1.4 GHz radio lobes have displaced the gas, compressing it into a shell that appears as bright cool arms. Finally we show that the large-scale radio emission detected with our VLA observations may be classified as a radio mini-halo, powered by the cooling flow (CF), as it nicely follows the trend P_radio vs. P_CF predicted by the...

  2. 7.1 keV sterile neutrino constraints from X-ray observations of 33 clusters of galaxies with Chandra ACIS

    CERN Document Server

    Hofmann, F; Nandra, K; Clerc, N; Gaspari, M

    2016-01-01

    Recently an unidentified emission line at 3.55 keV has been detected in X-ray spectra of clusters of galaxies. The line has been discussed as a possible decay signature of 7.1 keV sterile neutrinos, which have been proposed as a dark matter candidate. We aim at putting constraints on the proposed line emission in a large sample of Chandra-observed clusters and obtain limits on the mixing-angle in a 7.1 keV sterile neutrino dark matter scenario. For a sample of 33 high-mass clusters of galaxies we merge all observations from the Chandra data archive. Each cluster has more than 100 ks of combined exposure. The resulting high signal-to-noise spectra are used to constrain the flux of an unidentified line emission at 3.55 keV in the individual spectra and a merged spectrum of all clusters. We obtained very detailed spectra around the 3.55 keV range and limits on an unidentified emission line. Assuming all dark matter were made of 7.1 keV sterile neutrinos the upper limits on the mixing angle are $\\rm{sin^2(2\\Theta...

  3. Perturbative growth of cosmological clustering; 2, the two point correlation

    CERN Document Server

    Bharadwaj, S

    1995-01-01

    We use the BBGKY hierarchy equations to calculate, perturbatively, the lowest order nonlinear correction to the two point correlation and the pair velocity for Gaussian initial conditions in a critical density matter dominated cosmological model. We compare our results with the results obtained using the hydrodynamic equations which neglect pressure and we find that the two match, indicating that thare are no effects of multistreaming at this order of perturbation. We analytically study the effect of small scales on the large scales by calculating the nonlinear correction for a Dirac delta function initial two point correlation. We find that the induced two point correlation has a x^{-6} behaviour at large separations. We have considered a class of initial conditions where the initial power spectrum at small k has the form k^n with 0 < n \\le 3 and have numerically calculated the nonlinear correction to the two point correlation, its average over a sphere and the pair velocity over a large dynamical range. ...

  4. The Weak Lensing Signal and the Clustering of BOSS Galaxies: Cosmological Constraints

    CERN Document Server

    More, Surhud; Mandelbaum, Rachel; Takada, Masahiro; Spergel, David; Brownstein, Joel; Schneider, Donald P

    2014-01-01

    We perform a joint analysis of the abundance, the clustering and the galaxy-galaxy lensing signal of galaxies from Data Release 11 of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey. We fit halo occupation parameters and cosmological parameters ($\\Omega_m$ and $\\sigma_8$) to both of these observables simultaneously, and thus break the degeneracy between galaxy bias and cosmology. The cosmological analysis is the first of its kind to be performed at a redshift as high as 0.53. We present measurements of the clustering signal of galaxies by utilizing various stellar mass threshold samples. The galaxy-galaxy weak lensing signal is obtained by using the shape catalog of background galaxies from the Canada France Hawaii Telescope Legacy Survey, which was made publicly available by the CFHTLenS collaboration, with an area overlap of about 100 deg$^2$. We analyze these measurements in the framework of the halo model. Adopting a flat {\\Lambda}CDM cosmology with priors on $\\Omega_bh^2$, $n_s$ ...

  5. Cosmological constraints from the evolution of the cluster baryon mass function at z similar to 0.5

    DEFF Research Database (Denmark)

    Vikhlinin, A.; Voevodkin, A.; Mullis, C.R.;

    2003-01-01

    We present a new method for deriving cosmological constraints based on the evolution of the baryon mass function of galaxy clusters and implement it using 17 distant clusters from our 160 deg(2) ROSAT survey. The method uses the cluster baryon mass as a proxy for the total mass, thereby avoiding ...

  6. Fast Bayesian Semiparametric Curve-Fitting and Clustering in Massive Data With Application to Cosmology

    CERN Document Server

    Mukhopadhyay, Sabyasachi; Bhattacharya, Sourabh

    2009-01-01

    Recent technological advances have led to a flood of new data on cosmology rich in information about the formation and evolution of the universe, e.g., the data collected in Sloan Digital Sky Survey (SDSS) for more than 200 million objects. The analyses of such data demand cutting edge statistical technologies. Here, we have used the concept of mixture model within Bayesian semiparametric methodology to fit the regression curve with the bivariate data for the apparent magnitude and redshift for Quasars in SDSS (2007) catalogue. Associated with the mixture modeling is a highly efficient curve-fitting procedure, which is central to the application considered in this paper. Moreover, we adopt a new method for analysing the posterior distribution of clusterings, also generated as a by-product of our methodology. The results of our analysis of the cosmological data clearly indicate the existence of four change points on the regression curve andposssibiltiy of clustering of quasars specially at high redshift. This ...

  7. The entropy core in galaxy clusters: numerical and physical effects in cosmological grid simulations

    Science.gov (United States)

    Vazza, F.

    2011-01-01

    A flat distribution of low gas entropy in the core region of galaxy clusters is a feature commonly found in Eulerian cosmological simulations, at variance with most standard simulations of smoothed particle hydrodynamics fashion. From the literature, it is still unclear whether this difference is entirely due to numerical artefacts (e.g. spurious transfer from gravitational energy to thermal energy), physical mechanisms (e.g. enhanced mixing in Eulerian codes) or a mixture of both. This issue is related to many still open lines of research in the characterization of the dynamical evolution of the baryons in galaxy clusters: the origin of the cool-core/non-cool-core bi-modality, the diffusion of metals within galaxy clusters, the interplay between active galactic nuclei (AGN) and the intra-cluster medium, etc. In this work, we aim at constraining to what extent the entropy core is affected by numerical effects, and which are the physical reasons for its production in cosmological runs. To this end, we run a set of 30 high-resolution re-simulations of a ˜3 × 1014 M⊙ h-1 cluster of galaxies with a quiet dynamical history, using modified versions of the cosmological adaptive mesh refinement code ENZO and investigating many possible (physical and numerical) details involved in the production of entropy in simulated galaxy clusters. We report that the occurrence of a flat entropy core in the innermost region of a massive cluster is mainly due to hydrodynamical processes resolved by the numerical code (e.g. shocks and mixing motions) and that additional spurious effects of numerical origin (e.g. artificial heating due to softening effects) affect the size and level of the entropy core only in a minor way. Using Lagrangian tracers we show that the entropy profile of non-radiative simulations is produced by a mechanism of `sorting in entropy' which takes place with regularity during the cluster evolution. The evolution of tracers illustrates that the flat entropy core

  8. Formation of stars and clusters over cosmological time

    CERN Document Server

    Elmegreen, Bruce G

    2014-01-01

    The concept that stars form in the modern era began some 60 years ago with the key observation of expanding OB associations. Now we see that these associations are an intermediate scale in a cascade of hierarchical structures that begins on the ambient Jeans length close to a kiloparsec in size and continues down to the interiors of clusters, perhaps even to binary and multiple stellar systems. The origin of this structure lies with the dynamical nature of cloud and star formation, driven by supersonic turbulence and interstellar gravity. Dynamical star formation is relatively fast compared to the timescale for cosmic accretion, and then the star formation rate keeps up with the accretion rate, leading to a sequence of near-equilibrium states during galaxy formation and evolution. Dynamical star formation also helps to explain the formation of bound clusters, which require a local efficiency that exceeds the average by more than an order of magnitude. Efficiency increases with density in a hierarchically stru...

  9. Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts

    OpenAIRE

    Planck collaboration (incl. M. L. Brown, A. Bonaldi; Noviello, F.

    2014-01-01

    We present constraints on cosmological parameters using number counts as a function of redshift for a sub-sample of 189 galaxy clusters from the Planck SZ (PSZ) catalogue. The PSZ is selected through the signature of the Sunyaev-Zeldovich (SZ) effect, and the sub-sample used here has a signal-to-noise threshold of seven, with each object confirmed as a cluster and all but one with a redshift estimate. We discuss the completeness of the sample and our construction of a likelihood analysis. Usi...

  10. Cosmology and Astrophysics from Relaxed Galaxy Clusters V: Consistency with Cold Dark Matter Structure Formation

    CERN Document Server

    Mantz, Adam B; Morris, R Glenn

    2016-01-01

    This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the Cold Dark Matter (CDM) paradigm. We present constraints on the concentration--mass relation for massive clusters, finding a power-law mass dependence with a slope of $\\kappa_m=-0.16\\pm0.07$, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with $1+z$ of $\\kappa_\\zeta=-0.17\\pm0.26$), with an intrinsic scatter of $\\sigma_{\\ln c}=0.16\\pm0.03$. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically $\\sim50$kpc--1Mpc), and test for departures from the simple Navarro, Frenk & White (NFW...

  11. The evolution of clusters in the CLEF cosmological simulation: X-ray structural and scaling properties

    CERN Document Server

    Kay, S T; Aghanim, N; Blanchard, A; Liddle, A R; Puget, J L; Sadat, R; Thomas, P A; Kay, Scott T.; Silva, Antonio C. da; Aghanim, Nabila; Blanchard, Alain; Liddle, Andrew R.; Puget, Jean-Loup; Sadat, Rachida; Thomas, Peter A.

    2006-01-01

    We present results from a study of the X-ray cluster population that forms within the CLEF cosmological hydrodynamics simulation, a large N-body/SPH simulation of the Lambda CDM cosmology with radiative cooling, star formation and feedback. The scaled projected temperature and entropy profiles at z=0 are in good agreement with recent high-quality observations of cool core clusters, suggesting that the simulation grossly follows the processes that structure the intracluster medium (ICM) in these objects. Cool cores are a ubiquitous phenomenon in the simulation at low and high redshift, regardless of a cluster's dynamical state. This is at odds with the observations and so suggests there is still a heating mechanism missing from the simulation. Using a simple, observable measure of the concentration of the ICM, which correlates with the apparent mass deposition rate in the cluster core, we find a large dispersion within regular clusters at low redshift, but this diminishes at higher redshift, where strong "cool...

  12. Clusters of Galaxies as Probes for Precision Cosmology: Exploring the Limits using Numerical Simulations

    Science.gov (United States)

    Burns, J. O.; Motl, P. M.; Norman, M. L.; Hallman, E. J.

    2004-12-01

    We critically analyze the role of clusters of galaxies as probes for precision cosmology. Using synthetic observations of simulated clusters viewed through their X-ray emission and thermal Sunyaev-Zeldovich effect (SZE), we reduce the observations to attain measurements of the cluster gas mass and the Hubble constant. We utilize both parametric models such as the isothermal cluster model (and its generalizations to account for varying temperature profiles within the clusters) and non-parametric models that involve the geometric deprojection of the cluster emission assuming spherical symmetry. We are thus able to quantify the possible sources of uncertainty and systematic bias associated with the common simplifying assumptions used in reducing real cluster observations including isothermality and hydrostatic equilibrium. As a specific example, we find that the standard isothermal cluster model yields estimates of the Hubble constant that are systematically biased to low values. When we allow the temperature to vary in space, as in the polytropic cluster model, the X-ray and thermal SZE observations can be combined to produce an unbiased estimator of H0.

  13. Testing Gravity on Cosmological Scales with the Observed Abundance of Galaxy Clusters

    DEFF Research Database (Denmark)

    Rapetti Serra, David Angelo

    2011-01-01

    Using observations of the abundance of massive, X-ray flux-selected galaxy clusters, we obtain tight constraints on both the growth and expansion histories of the Universe. Our data set consists of 238 clusters detected by the ROSAT All-Sky Survey, and incorporates follow-up observations of 94......, and obtain improved constraints on departures from General Relativity (GR) on cosmological scales. We parameterize the linear growth rate of cosmic structure with a power law of the mean matter density to the growth index. Combining the X-ray cluster growth data with cluster gas-mass fraction, type Ia...... supernovae, baryon acoustic oscillations, and cosmic microwave background data we find a tight correlation between the growth index and the normalization of the matter power spectrum. Allowing the growth index and the dark energy equation of state parameter to take any constant values, we find no evidence...

  14. Cosmology and Astrophysics from Relaxed Galaxy Clusters III: Thermodynamic Profiles and Scaling Relations

    CERN Document Server

    Mantz, Adam B; Morris, R Glenn; Schmidt, Robert W

    2016-01-01

    This is the third in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot (i.e., massive) in Papers I and II of this series. Here we consider the thermodynamics of the intracluster medium, in particular the profiles of density, temperature and related quantities, as well as integrated measurements of gas mass, average temperature, total luminosity and center-excluded luminosity. We fit power-law scaling relations of each of these quantities as a function of redshift and cluster mass, which can be measured precisely and with minimal bias for these relaxed clusters. For the thermodynamic profiles, we jointly model the density and temperature and their intrinsic scatter as a function of radius, thus also capturing the behavior of the gas pressure and entropy. For the integrated quantities, we also jointly fit a multidimensional intrinsic covariance, providing the first observati...

  15. The discovery of lensed radio and X-ray sources behind the Frontier Fields cluster MACS J0717.5+3745 with the JVLA and Chandra

    CERN Document Server

    van Weeren, R J; Jones, C; Forman, W R; Andrade-Santos, F; Bonafede, A; Brüggen, M; Bulbul, E; Clarke, T E; Churazov, E; David, L; Dawson, W A; Donahue, M; Goulding, A; Kraft, R P; Mason, B; Merten, J; Mroczkowski, T; Murray, S S; Nulsen, P E J; Rosati, P; Roediger, E; Randall, S W; Sayers, J; Umetsu, K; Vikhlinin, A; Zitrin, A

    2015-01-01

    We report on high-resolution JVLA and Chandra observations of the HST Frontier Cluster MACS J0717.5+3745. MACS J0717.5+3745 offers the largest contiguous magnified area of any known cluster, making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0-6.5 GHz JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the HST imaging. Within this sample we find 7 lensed sources with amplification factors larger than $2$. None of these sources are identified as multiply-lensed. Based on the radio luminosities, the majority of these sources are likely star forming galaxies with star formation rates of 10-50 M$_\\odot$ yr$^{-1}$ located at $1 \\lesssim z \\lesssim 2$. Two of the lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely AGN, given their $2-10$ keV X-ray luminosities of $\\sim 10^{43-44}$ erg s$^{-1}$. From the derived radio luminosity function, we find evidence...

  16. The X-ray cluster survey with eROSITA: forecasts for cosmology, cluster physics, and primordial non-Gaussianity

    CERN Document Server

    Pillepich, Annalisa; Reiprich, Thomas H

    2011-01-01

    Starting in late 2013, the eROSITA telescope will survey the X-ray sky with unprecedented sensitivity. Assuming a detection limit of 50 photons in the (0.5-2.0) keV energy band with a typical exposure time of 1.6 ks, we predict that eROSITA will detect ~ 9.3 X 10^4 clusters of galaxies more massive than 5 X 10^13 Msun/h, with the currently planned all-sky survey. Their median redshift will be z ~ 0.35. We perform a Fisher-matrix analysis to forecast the constraining power of eROSITA on the LambdaCDM cosmology and, simultaneously, on the X-ray scaling relations for galaxy clusters. Special attention is devoted to the possibility of detecting primordial non-Gaussianity. We consider two experimental probes: the number counts and the angular clustering of a photon-count limited sample of clusters. We discuss how the cluster sample should be split to optimize the analysis and we show that redshift information of the individual clusters is vital to break the strong degeneracies among the model parameters. For examp...

  17. Challenges for Precision Cosmology with X-ray and Sunyaev-Zeldovich Effect Gas Mass Measurements of Galaxy Clusters

    OpenAIRE

    Hallman, Eric J.; Motl, Patrick M; Burns, Jack O.; Michael L. Norman

    2005-01-01

    We critically analyze the measurement of galaxy cluster gas masses, which is central to cosmological studies that rely on the galaxy cluster gas mass fraction. Using synthetic observations of numerically simulated clusters viewed through their X-ray emission and thermal Sunyaev-Zeldovich effect (SZE), we reduce the observations to obtain measurements of the cluster gas mass. We are thus able to quantify the possible sources of uncertainty and systematic bias associated with the common simplif...

  18. Planck 2015 results. XXIV. Cosmology from Sunyaev-Zeldovich cluster counts

    Science.gov (United States)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Bartolo, N.; Battaner, E.; Battye, R.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Comis, B.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Melin, J.-B.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Roman, M.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Türler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Weller, J.; White, S. D. M.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-09-01

    We present cluster counts and corresponding cosmological constraints from the Planck full mission data set. Our catalogue consists of 439 clusters detected via their Sunyaev-Zeldovich (SZ) signal down to a signal-to-noise ratio of 6, and is more than a factor of 2 larger than the 2013 Planck cluster cosmology sample. The counts are consistent with those from 2013 and yield compatible constraints under the same modelling assumptions. Taking advantage of the larger catalogue, we extend our analysis to the two-dimensional distribution in redshift and signal-to-noise. We use mass estimates from two recent studies of gravitational lensing of background galaxies by Planck clusters to provide priors on the hydrostatic bias parameter, (1-b). In addition, we use lensing of cosmic microwave background (CMB) temperature fluctuations by Planck clusters as an independent constraint on this parameter. These various calibrations imply constraints on the present-day amplitude of matter fluctuations in varying degrees of tension with those from the Planck analysis of primary fluctuations in the CMB; for the lowest estimated values of (1-b) the tension is mild, only a little over one standard deviation, while it remains substantial (3.7σ) for the largest estimated value. We also examine constraints on extensions to the base flat ΛCDM model by combining the cluster and CMB constraints. The combination appears to favour non-minimal neutrino masses, but this possibility does little to relieve the overall tension because it simultaneously lowers the implied value of the Hubble parameter, thereby exacerbating the discrepancy with most current astrophysical estimates. Improving the precision of cluster mass calibrations from the current 10%-level to 1% would significantly strengthen these combined analyses and provide a stringent test of the base ΛCDM model.

  19. Cosmology and astrophysics from relaxed galaxy clusters - V. Consistency with cold dark matter structure formation

    Science.gov (United States)

    Mantz, A. B.; Allen, S. W.; Morris, R. G.

    2016-10-01

    This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the cold dark matter (CDM) paradigm. We present constraints on the concentration-mass relation for massive clusters, finding a power-law mass dependence with a slope of κm = -0.16 ± 0.07, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with 1 + z of κζ = -0.17 ± 0.26), with an intrinsic scatter of σln c = 0.16 ± 0.03. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically ˜50 kpc-1 Mpc), and test for departures from the simple Navarro-Frenk-White (NFW) form, for which the logarithmic slope of the density profile tends to -1 at small radii. Specifically, we consider as alternatives the generalized NFW (GNFW) and Einasto parametrizations. For the GNFW model, we find an average value of (minus) the logarithmic inner slope of β = 1.02 ± 0.08, with an intrinsic scatter of σβ = 0.22 ± 0.07, while in the Einasto case we constrain the average shape parameter to be α = 0.29 ± 0.04 with an intrinsic scatter of σα = 0.12 ± 0.04. Our results are thus consistent with the simple NFW model on average, but we clearly detect the presence of intrinsic, cluster-to-cluster scatter about the average.

  20. Cosmological Constraints from a Combination of Galaxy Clustering and Lensing -- III. Application to SDSS Data

    CERN Document Server

    Cacciato, Marcello; More, Surhud; Mo, Houjun; Yang, Xiaohu

    2012-01-01

    We simultaneously constrain cosmology and galaxy bias using measurements of galaxy abundances, galaxy clustering and galaxy-galaxy lensing taken from the Sloan Digital Sky Survey. We use the conditional luminosity function (which describes the halo occupation statistics as function of galaxy luminosity) combined with the halo model (which describes the non-linear matter field in terms of its halo building blocks) to describe the galaxy-dark matter connection. We explicitly account for residual redshift space distortions in the projected galaxy-galaxy correlation functions, and marginalize over uncertainties in the scale dependence of the halo bias and the detailed structure of dark matter haloes. Under the assumption of a spatially flat, vanilla {\\Lambda}CDM cosmology, we focus on constraining the matter density, {\\Omega}m, and the normalization of the matter power spectrum, {\\sigma}8, and we adopt WMAP7 priors for the spectral index, the Hubble parameter, and the baryon density. We obtain that \\Omegam = 0.27...

  1. A statistically-selected Chandra sample of 20 galaxy clusters -- II. Gas properties and cool-core/non-cool core bimodality

    CERN Document Server

    Sanderson, Alastair J R; Ponman, Trevor J; ),

    2009-01-01

    We investigate the thermodynamic and chemical structure of the intracluster medium (ICM) across a statistical sample of 20 galaxy clusters analysed with the Chandra X-ray satellite. In particular, we focus on the scaling properties of the gas density, metallicity and entropy and the comparison between clusters with and without cool cores (CCs). We find marked differences between the two categories except for the gas metallicity, which declines strongly with radius for all clusters (Z ~ r^{-0.31}), outside ~0.02 r500. The scaling of gas entropy is non-self-similar and we find clear evidence of bimodality in the distribution of logarithmic slopes of the entropy profiles. With only one exception, the steeper sloped entropy profiles are found in CC clusters whereas the flatter slope population are all non-CC clusters. We explore the role of thermal conduction in stabilizing the ICM and conclude that this mechanism alone is sufficient to balance cooling in non-CC clusters. However, CC clusters appear to form a dis...

  2. 7.1 keV sterile neutrino constraints from X-ray observations of 33 clusters of galaxies with Chandra ACIS

    Science.gov (United States)

    Hofmann, F.; Sanders, J. S.; Nandra, K.; Clerc, N.; Gaspari, M.

    2016-08-01

    Context. Recently an unidentified emission line at 3.55 keV has been detected in X-ray spectra of clusters of galaxies. The line has been discussed as a possible decay signature of 7.1 keV sterile neutrinos, which have been proposed as a dark matter (DM) candidate. Aims: We aim to put constraints on the proposed line emission in a large sample of Chandra-observed clusters and obtain limits on the mixing angle in a 7.1 keV sterile neutrino DM scenario. Methods: For a sample of 33 high-mass clusters of galaxies, we merge all observations from the Chandra data archive. Each cluster has more than 100 ks of combined exposure. The resulting high signal-to-noise spectra are used to constrain the flux of an unidentified line emission at 3.55 keV in the individual spectra and a merged spectrum of all clusters. Results: We obtained very detailed spectra around the 3.55 keV range and limits on an unidentified emission line. Assuming all DM were made of 7.1 keV sterile neutrinos, the upper limits on the mixing angle are sin2(2Θ) < 10.1×10-11 from ACIS-I and < 40.3×10-11 from ACIS-S data at 99.7 per cent confidence level. Conclusions: We do not find evidence for an unidentified emission line at 3.55 keV. The sample extends the list of objects searched for an emission line at 3.55 keV and will help to identify the best targets for future studies of the potential DM decay line with upcoming X-ray observatories like Hitomi (Astro-H), eROSITA, and Athena.

  3. On finding galaxy clusters with PLANCK and the spherical collapse model in different dark energy cosmologies

    Energy Technology Data Exchange (ETDEWEB)

    Waizmann, Jean-Claude

    2010-11-24

    One of the main objectives of the PLANCK mission is to perform a full-sky cluster survey based on the Sunyaev-Zel'dovich (SZ) effect, which leads to the question of how such a survey would be affected by cosmological models with a different history of structure formation than LCDM. To answer this question, I developed a fast semi-analytic approach for simulating full-sky maps of the Compton-y parameter, ready to be fed into a realistic simulation pipeline. I also implemented a filter and detection pipeline based on spherical multi-frequency matched filters, that was used to study the expected SZ cluster sample of PLANCK. It turned out that realistic samples will comprise 1000 clusters at low rate of contamination, significantly lower than originally anticipated. Driven by wrong estimates of the impact of early dark energy models on structure formation, we studied the spherical collapse model in dark energy model, finding that models with varying equation-of-state have a negligible impact on the structure formation. Yet, the different expansion history for the different models can be detected via volume effects, when counting objects in a known volume. Furthermore, it turned out that the different expansion history strongly affects the angular SZ power spectra for the various models, making them an interesting tool to distinguish and constrain alternative cosmologies. (orig.)

  4. On finding galaxy clusters with PLANCK and the spherical collapse model in different dark energy cosmologies

    International Nuclear Information System (INIS)

    One of the main objectives of the PLANCK mission is to perform a full-sky cluster survey based on the Sunyaev-Zel'dovich (SZ) effect, which leads to the question of how such a survey would be affected by cosmological models with a different history of structure formation than LCDM. To answer this question, I developed a fast semi-analytic approach for simulating full-sky maps of the Compton-y parameter, ready to be fed into a realistic simulation pipeline. I also implemented a filter and detection pipeline based on spherical multi-frequency matched filters, that was used to study the expected SZ cluster sample of PLANCK. It turned out that realistic samples will comprise 1000 clusters at low rate of contamination, significantly lower than originally anticipated. Driven by wrong estimates of the impact of early dark energy models on structure formation, we studied the spherical collapse model in dark energy model, finding that models with varying equation-of-state have a negligible impact on the structure formation. Yet, the different expansion history for the different models can be detected via volume effects, when counting objects in a known volume. Furthermore, it turned out that the different expansion history strongly affects the angular SZ power spectra for the various models, making them an interesting tool to distinguish and constrain alternative cosmologies. (orig.)

  5. On the dynamical state of galaxy clusters: insights from cosmological simulations II.

    Science.gov (United States)

    Cui, Weiguang; Power, Chris; Borgani, Stefano; Knebe, Alexander; Lewis, Geraint F.; Murante, Giuseppe; Poole, Gregory B.

    2016-10-01

    Using a suite of cosmology simulations of a sample of >120 galaxy clusters with log (MDM, vir) ≤ 14.5. We compare clusters that form in purely dark matter run and their counterparts in hydro runs and investigate 4 independent parameters, that are normally used to classify dynamical state. We find that the virial ratio η in hydro-dynamical runs is ˜10 per cent lower than in the DM run, and there is no clear separation between the relaxed and unrelaxed clusters for any parameter. Further, using the velocity dispersion deviation parameter ζ, which is defined as the ratio between cluster velocity dispersion σ and the theoretical prediction σ _t = √{G M_{total}/R}, we find that there is a linear correlation between the virial ratio η and this ζ parameter. We propose to use this ζ parameter, which can be easily derived from observed galaxy clusters, as a substitute of the η parameter to quantify the cluster dynamical state.

  6. Cluster Structure in Cosmological Simulations I: Correlation to Observables, Mass Estimates, and Evolution

    CERN Document Server

    Jeltema, Tesla E; Burns, Jack O; Motl, Patrick M

    2007-01-01

    We use Enzo, a hybrid Eulerian AMR/N-body code including non-gravitational heating and cooling, to explore the morphology of the X-ray gas in clusters of galaxies and its evolution in current generation cosmological simulations. We employ and compare two observationally motivated structure measures: power ratios and centroid shift. Overall, the structure of our simulated clusters compares remarkably well to low-redshift observations, although some differences remain that may point to incomplete gas physics. We find no dependence on cluster structure in the mass-observable scaling relations, T_X-M and Y_X-M, when using the true cluster masses. However, estimates of the total mass based on the assumption of hydrostatic equilibrium, as assumed in observational studies, are systematically low. We show that the hydrostatic mass bias strongly correlates with cluster structure and, more weakly, with cluster mass. When the hydrostatic masses are used, the mass-observable scaling relations and gas mass fractions depen...

  7. On finding galaxy clusters with Planck and the spherical collapse model in different Dark Energy cosmologies

    OpenAIRE

    Waizmann, Jean-Claude

    2010-01-01

    One of the main objectives of the Planck mission is to perform a full-sky cluster survey based on the Sunyaev-Zel'dovich (SZ) effect, which leads to the question of how such a survey would be affected by cosmological models with a different history of structure formation than LCDM. To answer this question, I developed a fast semi-analytic approach for simulating full-sky maps of the Compton-y parameter, ready to be fed into a realistic simulation pipeline. I also implemented a filter and dete...

  8. A Chandra X-ray study of the young star cluster NGC 6231: low-mass population and initial mass function

    CERN Document Server

    Damiani, F; Sciortino, S

    2016-01-01

    NGC6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. We present high-spatial resolution Chandra ACIS-I X-ray data, where we detect 1613 point X-ray sources. Our main aim is to clarify global properties of NGC6231 down to low masses through a detailed membership assessment, and to study the cluster stars' spatial distribution, the origin of their X-ray emission, the cluster age and formation history, and initial mass function. We use X-ray data, complemented by optical/IR data, to establish cluster membership. The spatial distribution of different stellar subgroups also provides highly significant constraints on cluster membership, as does the distribution of X-ray hardness. We perform spectral modeling of group-stacked X-ray source spectra. We find a large cluster population down to ~0.3 Msun (complete to ~1 Msun), with minimal non-member contamination, with a definite age spread (1-8 ...

  9. The Discovery of Lensed Radio and X-Ray Sources behind the Frontier Fields Cluster MACS J0717.5+3745 with the JVLA and Chandra

    Science.gov (United States)

    van Weeren, R. J.; Ogrean, G. A.; Jones, C.; Forman, W. R.; Andrade-Santos, F.; Bonafede, A.; Brüggen, M.; Bulbul, E.; Clarke, T. E.; Churazov, E.; David, L.; Dawson, W. A.; Donahue, M.; Goulding, A.; Kraft, R. P.; Mason, B.; Merten, J.; Mroczkowski, T.; Murray, S. S.; Nulsen, P. E. J.; Rosati, P.; Roediger, E.; Randall, S. W.; Sayers, J.; Umetsu, K.; Vikhlinin, A.; Zitrin, A.

    2016-02-01

    We report on high-resolution JVLA and Chandra observations of the Hubble Space Telescope (HST) Frontier Cluster MACS J0717.5+3745. MACS J0717.5+3745 offers the largest contiguous magnified area of any known cluster, making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0-6.5 GHz JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the HST imaging. Within this sample, we find seven lensed sources with amplification factors larger than two. None of these sources are identified as multiply lensed. Based on the radio luminosities, the majority of these sources are likely star-forming galaxies with star-formation rates (SFRs) of 10-50 {M}⊙ yr-1 located at 1≲ z≲ 2. Two of the lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely active galactic nuclei, given their 2-10 keV X-ray luminosities of ˜1043-44 erg s-1. From the derived radio luminosity function, we find evidence for an increase in the number density of radio sources at 0.6\\lt z\\lt 2.0, compared to a z\\lt 0.3 sample. Our observations indicate that deep radio imaging of lensing clusters can be used to study star-forming galaxies, with SFRs as low as ˜10 M⊙ yr-1, at the peak of cosmic star formation history.

  10. The Atacama Cosmology Telescope (ACT): Beam Profiles and First SZ Cluster Maps

    CERN Document Server

    Hincks, A D; Ade, P; Aguirre, P; Amiri, M; Appel, J W; Barrientos, L F; Battistelli, E S; Bond, J R; Brown, B; Burger, B; Chervenak, J; Das, S; Devlin, M J; Dicker, S; Doriese, W B; Dunkley, J; Dünner, R; Essinger-Hileman, T; Fisher, R P; Fowler, J W; Hajian, A; Halpern, M; Hasselfield, M; Hernández-Monteagudo, C; Hilton, G C; Hilton, M; Hlozek, R; Huffenberger, K; Hughes, D; Hughes, J P; Infante, L; Irwin, K D; Jiménez, R; Juin, J B; Kaul, M; Klein, J; Kosowsky, A; Lau, J M; Limon, M; Lin, Y -T; Lupton, R H; Marriage, T; Marsden, D; Martocci, K; Mauskopf, P; Menanteau, F; Moodley, K; Moseley, H; Netterfield, C B; Niemack, M D; Nolta, M R; Page, L A; Parker, L; Partridge, B; Quintana, H; Reid, B; Sehgal, N; Sievers, J; Spergel, D N; Staggs, S T; Stryzak, O; Swetz, D; Switzer, E; Thornton, R; Trac, H; Tucker, C; Verde, L; Warne, R; Wilson, G; Wollack, E; Zhao, Y

    2009-01-01

    The Atacama Cosmology Telescope (ACT) is currently observing the cosmic microwave background with arcminute resolution at 148 GHz, 218 GHz, and 277 GHz. In this paper, we present ACT's first results. Data have been analyzed using a maximum-likelihood map-making method which uses B-splines to model and remove the atmospheric signal. It has been used to make high-precision beam maps from which we determine the experiment's window functions. This beam information directly impacts all subsequent analyses of the data. We also used the method to map a sample of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect, and show eight clusters previously detected in the X-ray or SZ and two new cluster candidates. We provide integrated Compton-y measurements for each cluster. Of particular interest is our detection of the z = 0.44 component of Abell 3128 and our current non-detection of the low-redshift part, providing strong evidence that the further cluster is more massive as suggested by X-ray measurements. This is a...

  11. The Chandra COSMOS Legacy Survey: Clustering of X-ray selected AGN at 2.9

    CERN Document Server

    Allevato, V; Finoguenov, A; Marchesi, S; Zamorani, G; Hasinger, G; Salvato, M; Miyaji, T; Gilli, R; Cappelluti, N; Brusa, M; Suh, H; Lanzuisi, G; Trakhtenbrot, B; Griffiths, R; Vignali, C; Schawinski, K; Karim, A

    2016-01-01

    We present the measurement of the projected and redshift space 2-point correlation function (2pcf) of the new catalog of Chandra COSMOS-Legacy AGN at 2.9$\\leq$z$\\leq$5.5 ($\\langle L_{bol} \\rangle \\sim$10$^{46}$ erg/s) using the generalized clustering estimator based on phot-z probability distribution functions (Pdfs) in addition to any available spec-z. We model the projected 2pcf estimated using $\\pi_{max}$ = 200 h$^{-1}$ Mpc with the 2-halo term and we derive a bias at z$\\sim$3.4 equal to b = 6.6$^{+0.60}_{-0.55}$, which corresponds to a typical mass of the hosting halos of log M$_h$ = 12.83$^{+0.12}_{-0.11}$ h$^{-1}$ M$_{\\odot}$. A similar bias is derived using the redshift-space 2pcf, modelled including the typical phot-z error $\\sigma_z$ = 0.052 of our sample at z$\\geq$2.9. Once we integrate the projected 2pcf up to $\\pi_{max}$ = 200 h$^{-1}$ Mpc, the bias of XMM and \\textit{Chandra} COSMOS at z=2.8 used in Allevato et al. (2014) is consistent with our results at higher redshift. The results suggest only...

  12. Clustering of Sloan Digital Sky Survey III Photometric Luminous Galaxies: The Measurement, Systematics and Cosmological Implications

    CERN Document Server

    Ho, Shirley; Seo, Hee-Jong; de Putter, Roland; Ross, Ashley J; White, Martin; Padmanabhan, Nikhil; Saito, Shun; Schlegel, David J; Schlafly, Eddie; Seljak, Uros; Hernandez-Monteagudo, Carlos; Sanchez, Ariel G; Percival, Will J; Blanton, Michael; Skibba, Ramin; Schneider, Don; Reid, Beth; Mena, Olga; Viel, Matteo; Eisenstein, Daniel J; Prada, Francisco; Weaver, Benjamin; Bahcall, Neta; Bizyaev, Dimitry; Brewinton, Howard; Brinkman, Jon; da Costa, Luiz Nicolaci; Gott, John R; Malanushenko, Elena; Malanushenko, Viktor; Nichol, Bob; Oravetz, Daniel; Pan, Kaike; Palanque-Delabrouille, Nathalie; Ross, Nicholas P; Simmons, Audrey; de Simoni, Fernando; Snedden, Stephanie; Yeche, Christophe

    2012-01-01

    The Sloan Digital Sky Survey (SDSS) surveyed 14,555 square degrees, and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between $z=0.45$ and $z=0.65$, constructed from the SDSS using methods described in Ross et al. (2011). This data-set spans 11,000 square degrees and probes a volume of $3h^{-3} \\rm{Gpc}^3$, making it the largest volume ever used for galaxy clustering measurements. We present a novel treatment of the observational systematics and its applications to the clustering signals from the data set. In this paper, we measure the angular clustering using an optimal quadratic estimator at 4 redshift slices with an accuracy of ~15% with bin size of delta_l = 10 on scales of the Baryon Acoustic Oscillations (BAO) (at l~40-400). We derive cosmological constraints using the full-shape of the power-spectra. For a flat Lambda CDM model, when combined with Cosmic Microwave Background Wilkinson Microw...

  13. The entropy core in galaxy clusters: numerical and physical effects in cosmological grid simulations

    CERN Document Server

    Vazza, F

    2010-01-01

    We investigated the numerical and physical reasons leading to a flat distribution of low gas entropy in the core region of galaxy clusters, as commonly found in grid cosmological simulations. To this end, we run a set of 30 high resolution re-simulations of a 3 x 10^14 M_sol/h cluster of galaxies with the AMR code ENZO, exploring and investigating the details involved in the production of entropy in simulated galaxy clusters. The occurrence of the flat entropy core is found to be mainly due to hydro-dynamical processes resolved in the code and that additional spurious effects of numerical origin (e.g. artificial heating due to softening effects or N-body noise) can affect the size and level of the entropy core only in a minor way. We show that the entropy profile of non-radiative simulations is produced by a mechanism of "sorting in entropy" which takes place with regularity during the cluster evolution. Using gas tracers we prove that the flat entropy core is caused by physical mixing of gravity-driven subso...

  14. Cosmological simulations of galaxy clusters with feedback from active galactic nuclei: profiles and scaling relations

    CERN Document Server

    Pike, Simon R; Newton, Richard D A; Thomas, Peter A; Jenkins, Adrian

    2014-01-01

    We present results from a new set of 30 cosmological simulations of galaxy clusters, including the effects of radiative cooling, star formation, supernova feedback, black hole growth and AGN feedback. We first demonstrate that our AGN model is capable of reproducing the observed cluster pressure profile at redshift, z~0, once the AGN heating temperature of the targeted particles is made to scale with the final virial temperature of the halo. This allows the ejected gas to reach larger radii in higher-mass clusters than would be possible had a fixed heating temperature been used. Such a model also successfully reduces the star formation rate in brightest cluster galaxies and broadly reproduces a number of other observational properties at low redshift, including baryon, gas and star fractions; entropy profiles outside the core; and the X-ray luminosity-mass relation. Our results are consistent with the notion that the excess entropy is generated via selective removal of the densest material through radiative c...

  15. The Atacama Cosmology Telescope (ACT): Beam Profiles and First SZ Cluster Maps

    Science.gov (United States)

    Hincks, A. D.; Acquaviva, V.; Ade, P. A.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Battistelli, E. S.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Doriese, W. B.; Dunkley, J.; Duenner, R.; Essinger-Hileman, T.; Fisher, R. P.; Fowler, J. W.; Hajian, A.; Halpern, M.; Hasselfield, M.; Wollack, Ed

    2010-01-01

    The Atacama Cosmology Telescope (ACT) is currently observing the cosmic microwave background with arcminute resolution at 148 GHz, 218 GHz, and 277 GHz, In this paper, we present ACT's first results. Data have been analyzed using a maximum-likelihood map-making method which uses B-splines to model and remove the atmospheric signal. It has been used to make high-precision beam maps from which we determine the experiment's window functions, This beam information directly impacts all subsequent analyses of the data. We also used the method to map a sample of galaxy clusters via the Sunyaev-Ze1'dovich (SZ) effect, and show five clusters previously detected with X-ray or SZ observations, We provide integrated Compton-y measurements for each cluster. Of particular interest is our detection of the z = 0.44 component of A3128 and our current non-detection of the low-redshift part, providing strong evidence that the further cluster is more massive as suggested by X-ray measurements. This is a compelling example of the redshift-independent mass selection of the SZ effect.

  16. Suzaku and Chandra Observations of CIZA J1700.8$-$3144, a Cluster of Galaxies in the Zone of Avoidance

    CERN Document Server

    Mori, Hideyuki; Ueda, Yoshihiro; Nakazawa, Kazuhiro; Tawara, Yuzuru

    2016-01-01

    We present the Chandra and Suzaku observations of 1RXS J170047.8$-$314442, located towards the Galactic bulge, to reveal a wide-band ($0.3$-$10$ keV) X-ray morphology and spectrum of this source. With the Chandra observation, no point source was found at the position of 1RXS J170047.8$-$314442. Alternatively, we revealed the presence of diffuse X-ray emission by the wide-band X-ray image obtained from the Suzaku XIS. Although the X-ray emission had a nearly circular shape with a spatial extent of $\\sim 3.5'$, the surface brightness profile was not axisymmetric; a bright spot-like emission was found at $\\sim 1'$ away in the north-western direction from the center. The radial profile of the surface brightness, except for this spot-like emission, was reproduced with a single $\\beta$-model; $\\beta$ and the core radius were found to be $1.02$ and $1.51'$, respectively. The X-ray spectrum of the diffuse emission showed an emission line at $\\sim 6$ keV, indicating an origin of a thermal plasma. The spectrum was well...

  17. The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Angular clustering tomography and its cosmological implications

    CERN Document Server

    Salazar-Albornoz, Salvador; Grieb, Jan Niklas; Crocce, Martin; Scoccimarro, Roman; Alam, Shadab; Beutler, Florian; Brownstein, Joel R; Chuang, Chia-Hsun; Kitaura, Francisco-Shu; Olmstead, Matthew D; Percival, Will J; Prada, Francisco; Rodríguez-Torres, Sergio; Samushia, Lado; Tinker, Jeremy; Thomas, Daniel; Tojeiro, Rita; Wang, Yuting; Zhao, Gong-bo

    2016-01-01

    We investigate the cosmological implications of studying galaxy clustering using a tomographic approach applied to the final BOSS DR12 galaxy sample, including both auto- and cross-correlation functions between redshift shells. We model the signal of the full shape of the angular correlation function, $\\omega(\\theta)$, in redshift bins using state-of-the-art modelling of non-linearities, bias and redshift-space distortions. We present results on the redshift evolution of the linear bias of BOSS galaxies, which cannot be obtained with traditional methods for galaxy-clustering analysis. We also obtain constraints on cosmological parameters, combining this tomographic analysis with measurements of the cosmic microwave background (CMB) and type Ia supernova (SNIa). We explore a number of cosmological models, including the standard $\\Lambda$CDM model and its most interesting extensions, such as deviations from $w_\\rm{DE} = -1$, non-minimal neutrino masses, spatial curvature and deviations from general relativity u...

  18. The formation of the brightest cluster galaxies in cosmological simulations: the case for active galactic nucleus feedback

    OpenAIRE

    Martizzi, Davide; Teyssier, Romain; Moore, Ben

    2012-01-01

    We use 500 pc resolution cosmological simulations of a Virgo-like galaxy cluster to study the properties of the brightest cluster galaxy (BCG) that forms at the centre of the halo. We compared two simulations; one incorporating only supernova feedback and a second that also includes prescriptions for black hole growth and the resulting active galactic nucleus (AGN) feedback from gas accretion. As previous work has shown, with supernova feedback alone we are unable to reproduce any of the obse...

  19. Cosmological parameter estimation from CMB and X-ray cluster after Planck

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jian-Wei; Cai, Rong-Gen; Guo, Zong-Kuan [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China); Hu, Bin, E-mail: jwhu@itp.ac.cn, E-mail: cairg@itp.ac.cn, E-mail: guozk@itp.ac.cn, E-mail: hu@lorentz.leidenuniv.nl [Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, 2333 CA Leiden (Netherlands)

    2014-05-01

    We investigate constraints on cosmological parameters in three 8-parameter models with the summed neutrino mass as a free parameter, by a joint analysis of CCCP X-ray cluster data, the newly released Planck CMB data as well as some external data sets including baryon acoustic oscillation measurements from the 6dFGS, SDSS DR7 and BOSS DR9 surveys, and Hubble Space Telescope H{sub 0} measurement. We find that the combined data strongly favor a non-zero neutrino masses at more than 3σ confidence level in these non-vanilla models. Allowing the CMB lensing amplitude A{sub L} to vary, we find A{sub L} > 1 at 3σ confidence level. For dark energy with a constant equation of state w, we obtain w < −1 at 3σ confidence level. The estimate of the matter power spectrum amplitude σ{sub 8} is discrepant with the Planck value at 2σ confidence level, which reflects some tension between X-ray cluster data and Planck data in these non-vanilla models. The tension can be alleviated by adding a 9% systematic shift in the cluster mass function.

  20. Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts

    CERN Document Server

    Ade, P.A.R.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Barrena, R.; Bartlett, J.G.; Battaner, E.; Battye, R.; Benabed, K.; Benoit, A.; Benoit-Levy, A.; Bernard, J.P.; Bersanelli, M.; Bielewicz, P.; Bikmaev, I.; Blanchard, A.; Bobin, J.; Bock, J.J.; Bohringer, H.; Bonaldi, A.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Bourdin, H.; Bridges, M.; Brown, M.L.; Bucher, M.; Burenin, R.; Burigana, C.; Butler, R.C.; Cardoso, J.F.; Carvalho, P.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.R.; Chiang, L.Y.; Chiang, H.C.; Chon, G.; Christensen, P.R.; Church, S.; Clements, D.L.; Colombi, S.; Colombo, L.P.L.; Couchot, F.; Coulais, A.; Crill, B.P.; Curto, A.; Cuttaia, F.; Da Silva, A.; Dahle, H.; Danese, L.; Davies, R.D.; Davis, R.J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.M.; Democles, J.; Desert, F.X.; Dickinson, C.; Diego, J.M.; Dolag, K.; Dole, H.; Donzelli, S.; Dore, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Ensslin, T.A.; Eriksen, H.K.; Finelli, F.; Flores-Cacho, I.; Forni, O.; Frailis, M.; Franceschi, E.; Fromenteau, S.; Galeotta, S.; Ganga, K.; Genova-Santos, R.T.; Giard, M.; Giardino, G.; Giraud-Heraud, Y.; Gonzalez-Nuevo, J.; Gorski, K.M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F.K.; Hanson, D.; Harrison, D.; Henrot-Versille, S.; Hernandez-Monteagudo, C.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hobson, M.; Holmes, W.A.; Hornstrup, A.; Hovest, W.; Huffenberger, K.M.; Hurier, G.; Jaffe, T.R.; Jaffe, A.H.; Jones, W.C.; Juvela, M.; Keihanen, E.; Keskitalo, R.; Khamitov, I.; Kisner, T.S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lahteenmaki, A.; Lamarre, J.M.; Lasenby, A.; Laureijs, R.J.; Lawrence, C.R.; Leahy, J.P.; Leonardi, R.; Leon-Tavares, J.; Lesgourgues, J.; Liddle, A.; Liguori, M.; Lilje, P.B.; Linden-Vornle, M.; Lopez-Caniego, M.; Lubin, P.M.; Macias-Perez, J.F.; Maffei, B.; Maino, D.; Mandolesi, N.; Marcos-Caballero, A.; Maris, M.; Marshall, D.J.; Martin, P.G.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Meinhold, P.R.; Melchiorri, A.; Melin, J.B.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschenes, M.A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C.B.; Norgaard-Nielsen, H.U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C.A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G.W.; Prezeau, G.; Prunet, S.; Puget, J.L.; Rachen, J.P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Roman, M.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rubino-Martin, J.A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M.D.; Shellard, E.P.S.; Spencer, L.D.; Starck, J.L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.S.; Sygnet, J.F.; Tauber, J.A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Turler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L.A.; Wandelt, B.D.; Weller, J.; White, M.; White, S.D.M.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-01-01

    We present constraints on cosmological parameters using number counts as a function of redshift for a sub-sample of 189 galaxy clusters from the Planck SZ (PSZ) catalogue. The PSZ is selected through the signature of the Sunyaev--Zeldovich (SZ) effect, and the sub-sample used here has a signal-to-noise threshold of seven, with each object confirmed as a cluster and all but one with a redshift estimate. We discuss the completeness of the sample and our construction of a likelihood analysis. Using a relation between mass $M$ and SZ signal $Y$ calibrated to X-ray measurements, we derive constraints on the power spectrum amplitude $\\sigma_8$ and matter density parameter $\\Omega_{\\mathrm{m}}$ in a flat $\\Lambda$CDM model. We test the robustness of our estimates and find that possible biases in the $Y$--$M$ relation and the halo mass function are larger than the statistical uncertainties from the cluster sample. Assuming the X-ray determined mass to be biased low relative to the true mass by between zero and 30%, m...

  1. The Atacama Cosmology Telescope: The LABOCA/ACT Survey of Clusters at All Redshifts

    CERN Document Server

    Lindner, Robert R; Baker, Andrew J; Bond, J Richard; Crichton, Devin; Devlin, Mark J; Essinger-Hileman, Thomas; Hilton, Matt; Hincks, Adam D; Huffenberger, Kevin M; Hughes, John P; Infante, Leopoldo; Lima, Marcos; Marriage, Tobias A; Menanteau, Felipe; Niemack, Michael D; Page, Lyman A; Schmitt, Benjamin L; Sehgal, Neelima; Sievers, J L; Sifón, Cristóbal; Staggs, Suzanne T; Swetz, Daniel; Weiß, Axel; Wollack, Edward J

    2014-01-01

    We present a multi-wavelength analysis of eleven Sunyaev Zel'dovich effect (SZE)-selected galaxy clusters (ten with new data) from the Atacama Cosmology Telescope (ACT) southern survey. We have obtained new imaging from the Large APEX Bolometer Camera (345GHz; LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope, the Australia Telescope Compact Array (2.1GHz; ATCA), and the Spectral and Photometric Imaging Receiver (250, 350, and $500\\,\\rm\\mu m$; SPIRE) on the Herschel Space Observatory. Spatially-resolved 345GHz SZE increments with integrated S/N > 5 are found in six clusters. We compute 2.1GHz number counts as a function of cluster-centric radius and find significant enhancements in the counts of bright sources at projected radii $\\theta < \\theta_{2500}$. By extrapolating in frequency, we predict that the combined signals from 2.1GHz-selected radio sources and 345GHz-selected SMGs contaminate the 148GHz SZE decrement signal by ~5% and the 345GHz SZE increment by ~18%. After removing radio source...

  2. Stable clustering and the resolution of dissipationless cosmological N-body simulations

    CERN Document Server

    Benhaiem, David; Labini, Francesco Sylos

    2016-01-01

    The determination of the resolution of cosmological N-body simulations, i.e., the range of scales in which quantities measured in them represent accurately the continuum limit, is an important open question. We address it here using scale-free models, for which self-similarity provides a powerful tool to control resolution. Such models also provide a robust testing ground for the so-called stable clustering approximation, which gives simple predictions for them. Studying large N-body simulations of such models with different force smoothing, we find that these two issues are in fact very closely related: our conclusion is that resolution in the non-linear regime extends, in practice, down to the scale at which stable clustering breaks down. Physically the association of the two scales is in fact simple to understand: stable clustering fails to be a good approximation when there are strong interactions of structures (in particular merging) and it is precisely such non-linear processes which are sensitive to fl...

  3. A Deep and Ultra-deep ISOCAM Cosmological Survey through Gravitationally Lensing Clusters of Galaxies

    CERN Document Server

    Metcalfe, L; McBreen, B; Kneib, J P; Delaney, M; Biviano, A; Kessler, M F; Leech, K J; Okumura, K; Schulz, B; Elbaz, D; Aussel, H

    1999-01-01

    We present imaging results and source counts from an ISOCAM deep and ultra-deep cosmological survey through gravitationally lensing clusters of galaxies at 7 and 15 microns. A total area of about 53 sq.arcmin was covered in maps of three clusters. The lensing increases the sensitivity of the survey. A large number of luminous mid-infrared (MIR) sources were detected behind the lenses, and most could be unambiguously identified with visible counterparts. Thanks to the gravitational amplification, these results include the faintest MIR detections ever recorded, extending source counts to an unprecedented level. The source counts, corrected for cluster contamination and lensing distortion effects, show an excess by a factor of 10 with respect to the prediction of a no-evolution model, as we reported for A2390 alone in Altieri et al. (1999). We confirm the A2390 result that the resolved 7 and 15 microns background radiation intensities are 2 (+/- 0.5) x 10^-9 and 5 (+/- 1) x 10^-9 W/m^2/sr, respectively.

  4. New Results from Chandra

    CERN Document Server

    Forman, W; Jones, C; Vikhlinin, A A; Churazov, E

    2001-01-01

    We discuss two themes from Chandra observations of galaxies and clusters. First, we describe the effects of radio-emitting plasmas or ``bubbles'', inflated by active galactic nuclei, on the hot X-ray emitting gaseous atmospheres in galaxies and clusters. We describe the interaction of the ``bubbles'' and the X-ray emitting gas as the buoyant bubbles rise through the hot gas. Second, we describe sharp, edge-like surface brightness structures in clusters. Chandra observations show that these features are not shock fronts as was originally thought, but ``cold fronts'', most likely the boundaries of the remaining cores of merger components. Finally, we present recent observations of M86 and NGC507 which show similar sharp features around galaxies. For M86, the sharp edge is the boundary between the galaxy's X-ray corona and the Virgo cluster gas. The structures around NGC507, the central galaxy in a group, could be relics of galaxy formation or may reflect the motion of NGC507 in the larger potential of the group...

  5. Chandra Catches "Piranha" Black Holes

    Science.gov (United States)

    2007-07-01

    Supermassive black holes have been discovered to grow more rapidly in young galaxy clusters, according to new results from NASA's Chandra X-ray Observatory. These "fast-track" supermassive black holes can have a big influence on the galaxies and clusters that they live in. Using Chandra, scientists surveyed a sample of clusters and counted the fraction of galaxies with rapidly growing supermassive black holes, known as active galactic nuclei (or AGN). The data show, for the first time, that younger, more distant galaxy clusters contained far more AGN than older, nearby ones. Galaxy clusters are some of the largest structures in the Universe, consisting of many individual galaxies, a few of which contain AGN. Earlier in the history of the universe, these galaxies contained a lot more gas for star formation and black hole growth than galaxies in clusters do today. This fuel allows the young cluster black holes to grow much more rapidly than their counterparts in nearby clusters. Illustration of Active Galactic Nucleus Illustration of Active Galactic Nucleus "The black holes in these early clusters are like piranha in a very well-fed aquarium," said Jason Eastman of Ohio State University (OSU) and first author of this study. "It's not that they beat out each other for food, rather there was so much that all of the piranha were able to really thrive and grow quickly." The team used Chandra to determine the fraction of AGN in four different galaxy clusters at large distances, when the Universe was about 58% of its current age. Then they compared this value to the fraction found in more nearby clusters, those about 82% of the Universe's current age. The result was the more distant clusters contained about 20 times more AGN than the less distant sample. AGN outside clusters are also more common when the Universe is younger, but only by factors of two or three over the same age span. "It's been predicted that there would be fast-track black holes in clusters, but we never

  6. Photometric and clustering properties of hydrodynamical galaxies in a cosmological volume: results at z = 0

    Science.gov (United States)

    Nuza, Sebastián E.; Dolag, Klaus; Saro, Alexandro

    2010-09-01

    In this work, we present results for the photometric and clustering properties of galaxies that arise in a Λ cold dark matter hydrodynamical simulation of the local Universe. The present-day distribution of matter was constructed to match the observed large-scale pattern of the IRAS 1.2-Jy galaxy survey. Our simulation follows the formation and evolution of galaxies in a cosmological sphere with a volume of ~1303h-3Mpc3 including supernova feedback, galactic winds, photoheating due to a uniform meta-galactic background and chemical enrichment of the gas and stellar populations. However, we do not consider active galactic nuclei. In the simulation, a total of ~20000 galaxies are formed above the resolution limit, and around 60 haloes are more massive than ~1014Msolar. Luminosities of the galaxies are calculated based on a stellar population synthesis model including the attenuation by dust, which is calculated from the cold gas left within the simulated galaxies. Environmental effects such as colour bimodality and differential clustering power of the hydrodynamical galaxies are qualitatively similar to observed trends. Nevertheless, the overcooling present in the simulations leads to too blue and overluminous brightest cluster galaxies (BCGs). To overcome this, we mimic the late-time suppression of star formation in massive haloes by ignoring recently formed stars with the aid of a simple post-processing recipe. In this way we find luminosity functions, both for field and for group/cluster galaxies, in better agreement with observations. Specifically, the BCGs then follow the observed luminosity-halo mass relation. However, in such a case, the colour bimodality is basically lost, pointing towards a more complex interplay of late suppression of star formation than what is given by the simple scheme adopted.

  7. Cosmology from Large Scale Galaxy Clustering and Galaxy-Galaxy Lensing with Dark Energy Survey Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Kwan, J.; et al.

    2016-04-26

    We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as $\\Omega_m = 0.31 \\pm 0.09$ and the clustering amplitude of the matter power spectrum as $\\sigma_8 = 0.74 +\\pm 0.13$ after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into $S_8$ = $\\sigma_8(\\Omega_m/0.3)^{0.16} = 0.74 \\pm 0.12$ for our fiducial lens redshift bin at 0.35 < z < 0.5, while $S_8 = 0.78 \\pm 0.09$ using two bins over the range 0.2 < z < 0.5. We study the robustness of the results under changes in the data vectors, modelling and systematics treatment, including photometric redshift and shear calibration uncertainties, and find consistency in the derived cosmological parameters. We show that our results are consistent with previous cosmological analyses from DES and other data sets and conclude with a joint analysis of DES angular clustering and galaxy-galaxy lensing with Planck CMB data, Baryon Accoustic Oscillations and Supernova type Ia measurements.

  8. Fundamental Limitations on Cosmological Clustering Simulations Due to "N-Bodies"

    CERN Document Server

    Splinter, R J; Shandarin, S F; Suto, Y; Splinter, Randall J.; Melott, Adrian L.; Shandarin, Sergei F.; Suto, Yasushi

    1998-01-01

    Fundamental physical considerations and past tests suggest that there may be a problem with discreteness error in N--body methods widely used in cosmological clustering studies. We study such effects by comparison tests, using identical initial conditions but variable code parameters in PM, P$^3$M, and Tree. We study mass resolution, which most "high resolution" codes lack. We compare the power spectrum $P(k)$, two-point correlation function $\\xi(r)$, mean pairwise velocity and pairwise dispersion, cluster analysis, genus, cross-correlation of density fields, divergent orbits, and phase correlations. As particles are added, but the absolute scale of the force resolution is held constant, the P$^3$M and the Tree runs agree more and more strongly with each other and with the PM run, suggesting that the time integration is converging. However, they do not particularly converge to another PM run which continued power law fluctuations to small scales (which is possible given more particles) unless the evolved fiel...

  9. The Impact of Galaxy Cluster Mergers on Cosmological Parameter Estimation from Surveys of the Sunyaev-Zel'dovich Effect

    OpenAIRE

    Wik, Daniel R.; Sarazin, Craig L.; Ricker, Paul M.; Randall, Scott W.

    2008-01-01

    Sensitive surveys of the Cosmic Microwave Background will detect thousands of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect. Two SZ observables, the central or maximum and integrated Comptonization parameters y_max and Y, relate in a simple way to the total cluster mass, which allow the construction of mass functions (MFs) that can be used to estimate cosmological parameters such as Omega_M, sigma_8, and the dark energy parameter w. However, clusters form from the mergers of smaller ...

  10. A new (2+1)D cluster finding algorithm based on photometric redshifts: large scale structure in the Chandra Deep Field South

    CERN Document Server

    Trevese, D; Fontana, A; Giallongo, E; Trevese, Dario; Castellano, Marco; Fontana, Adriano; Giallongo, Emanuele

    2006-01-01

    Aims: We study galaxy clustering and explore the dependence of galaxy properties on the the environment up to a redshift z~1, on the basis of a deep multi-band survey in the Chandra Deep Field South. Methods: We have developed a new method which combines galaxy angular positions and photometric redshifts to estimate the local galaxy number-density. This allows both the detection of overdensities in the galaxy distribution and the study of the properties of the galaxy population as a function of the environmental density. Results: We detect two moderate overdensities at z~0.7 and z~1 previously identified spectroscopically. We find that the fraction of red galaxies within each structure increases with volume density, extending to z~1 previous results. We measure ``red sequence'' slopes consistent with the values found in X-ray selected clusters, supporting the notion that the mass-metallicity relation hold constant up to z~1. Conclusions: Our method based on photometric redshifts allows to extend structure det...

  11. The extended ROSAT-ESO Flux-Limited X-ray Galaxy Cluster Survey (REFLEX II) VI. Effect of massive neutrinos on the cosmological constraints from clusters

    CERN Document Server

    Boehringer, Hans

    2015-01-01

    Clusters of galaxies are important probes for the large-scale structure that allow us to test cosmological models. With the REFLEX II galaxy cluster survey we previously derived tight constraints on the cosmological parameters for the matter density, Omega_m, and the amplitude parameter of the matter density fluctuations, sigma_8. Whereas in these previous studies no effect of massive neutrinos was taken into account, we explore these effects in the present publication. We derive cosmological constraints for the sum of the neutrino masses of the conventional three neutrino families in the range 0 to 0.6 eV. The influence on the constraints of Omega_m and sigma_8 for the expected mass range is weak. Interesting constraints on the neutrino properties can be derived by comparing the cluster data with those from the Planck cosmic microwave background observations. The current tension between the Planck results and clusters can formally be resolved with neutrino masses of about M_nu = 0.45 (+- 0.28, 1-sigma) eV. W...

  12. Adaptive Mesh Refinement Cosmological Simulations of Cosmic Rays in Galaxy Clusters

    Science.gov (United States)

    Skillman, Samuel William

    2013-12-01

    Galaxy clusters are unique astrophysical laboratories that contain many thermal and non-thermal phenomena. In particular, they are hosts to cosmic shocks, which propagate through the intracluster medium as a by-product of structure formation. It is believed that at these shock fronts, magnetic field inhomogeneities in a compressing flow may lead to the acceleration of cosmic ray electrons and ions. These relativistic particles decay and radiate through a variety of mechanisms, and have observational signatures in radio, hard X-ray, and Gamma-ray wavelengths. We begin this dissertation by developing a method to find shocks in cosmological adaptive mesh refinement simulations of structure formation. After describing the evolution of shock properties through cosmic time, we make estimates for the amount of kinetic energy processed and the total number of cosmic ray protons that could be accelerated at these shocks. We then use this method of shock finding and a model for the acceleration of and radio synchrotron emission from cosmic ray electrons to estimate the radio emission properties in large scale structures. By examining the time-evolution of the radio emission with respect to the X-ray emission during a galaxy cluster merger, we find that the relative timing of the enhancements in each are important consequences of the shock dynamics. By calculating the radio emission expected from a given mass galaxy cluster, we make estimates for future large-area radio surveys. Next, we use a state-of-the-art magnetohydrodynamic simulation to follow the electron acceleration in a massive merging galaxy cluster. We use the magnetic field information to calculate not only the total radio emission, but also create radio polarization maps that are compared to recent observations. We find that we can naturally reproduce Mpc-scale radio emission that resemble many of the known double radio relic systems. Finally, motivated by our previous studies, we develop and introduce a

  13. Constraints on Scalar-Field Dark Energy from Galaxy Cluster Gas Mass Fraction versus Redshift

    OpenAIRE

    Chen, Gang; Ratra, Bharat

    2004-01-01

    We use the Allen et al. (2004) Chandra measurements of x-ray gas mass fraction of 26 rich clusters to place constraints on the scalar-field dark energy model with inverse power law potential energy density. The constraints are consistent with, and typically more constraining than, those from other cosmological tests, and mildly favor the Einstein cosmological constant limit of the dark energy model.

  14. Cosmology from large scale galaxy clustering and galaxy-galaxy lensing with Dark Energy Survey Science Verification data

    Science.gov (United States)

    Kwan, J.; Sánchez, C.; Clampitt, J.; Blazek, J.; Crocce, M.; Jain, B.; Zuntz, J.; Amara, A.; Becker, M. R.; Bernstein, G. M.; Bonnett, C.; DeRose, J.; Dodelson, S.; Eifler, T. F.; Gaztanaga, E.; Giannantonio, T.; Gruen, D.; Hartley, W. G.; Kacprzak, T.; Kirk, D.; Krause, E.; MacCrann, N.; Miquel, R.; Park, Y.; Ross, A. J.; Rozo, E.; Rykoff, E. S.; Sheldon, E.; Troxel, M. A.; Wechsler, R. H.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Benoit-Lévy, A.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Carrasco Kind, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Evrard, A. E.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jarvis, M.; Kuehn, K.; Lahav, O.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Melchior, P.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.

    2016-10-01

    We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as Ωm = 0.31 ± 0.09 and the clustering amplitude of the matter power spectrum as σ8 = 0.74 ± 0.13 after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into S8 ≡ σ8(Ωm/0.3)0.16 = 0.74 ± 0.12 for our fiducial lens redshift bin at 0.35 CMB data, Baryon Accoustic Oscillations and Supernova type Ia measurements.

  15. Contributions of the NASA's Chandra X-Ray Observatory

    Science.gov (United States)

    Weisskopf, Martin C.

    2011-01-01

    NASA's Chandra X-ray Observatory performed its first observations over a decade ago. Chandra's spectacular images and detailed spectra of astrophysical systems ranging from solar system objects to distant galaxies and galaxy clusters have provided information on such diverse topics as the properties of planetary and cometary atmospheres, stellar formation and demise, black hole-galaxy-cluster interactions, and properties of dark matter and dark energy. This presentation highlights some discoveries made with Chandra and briefly discusses future prospects.

  16. Spatial Correlation Function of the Chandra Selected Active Galactic Nuclei

    Science.gov (United States)

    Yang, Y.; Mushotzky, R. F.; Barger, A. J.; Cowie, L. L.

    2006-01-01

    We present the spatial correlation function analysis of non-stellar X-ray point sources in the Chandra Large Area Synoptic X-ray Survey of Lockman Hole Northwest (CLASXS). Our 9 ACIS-I fields cover a contiguous solid angle of 0.4 deg(exp 2) and reach a depth of 3 x 10(exp -15) erg/square cm/s in the 2-8 keV band. We supplement our analysis with data from the Chandra Deep Field North (CDFN). The addition of this field allows better probe of the correlation function at small scales. A total of 233 and 252 sources with spectroscopic information are used in the study of the CLASXS and CDFN fields respectively. We calculate both redshift-space and projected correlation functions in co-moving coordinates, averaged over the redshift range of 0.1 luminosity and clustering amplitude is weak, which, however, is fully consistent with the expectation using the simplest relations between X-ray luminosity, black hole mass, and dark halo mass. We study the evolution of the AGN clustering by dividing the samples into 4 redshift bins over 0.1 Mpcmass of the dark matter halo derived from the bias estimates show little change with redshift. The average halo mass is found to be log (M(sub halo)/M(sun))approximates 12.1. Subject headings: cosmology: observations - large-scale structure of the universe - x-rays: diffuse background - galaxies: nuclei

  17. Cosmic Ray Protons Accelerated at Cosmological Shocks and Their Impact on Groups and Clusters of Galaxies

    CERN Document Server

    Miniati, F; Kang, H; Jones, T W; Miniati, Francesco; Ryu, Dongsu; Kang, Hyesung

    2001-01-01

    We investigate the production of cosmic ray (CR) protons at cosmological shocks by performing, for the first time, numerical simulations of large scale structure formation that include directly the acceleration, transport and energy losses of the high energy particles. CRs are injected at shocks according to the thermal leakage model and, thereafter, accelerated to a power-law distribution as indicated by the test particle limit of the diffusive shock acceleration theory. The evolution of the CR protons accounts for losses due to adiabatic expansion/compression, Coulomb collisions and inelastic p-p scattering. Our results suggest that CR protons produced at shocks formed in association with the process of large scale structure formation could amount to a substantial fraction of the total pressure in the intra-cluster medium. Their presence should be easily revealed by GLAST through detection of gamma-ray flux from the decay of neutral pions produced in inelastic p-p collisions of such CR protons with nuclei o...

  18. Photometric and clustering properties of hydrodynamical galaxies in a cosmological volume: results at z=0

    CERN Document Server

    Nuza, S E; Saro, A

    2010-01-01

    In this work, we present results for the photometric and clustering properties of galaxies that arise in a LambdaCDM hydrodynamical simulation of the local Universe. The present-day distribution of matter was constructed to match the observed large scale pattern of the IRAS 1.2-Jy galaxy survey. Our simulation follows the formation and evolution of galaxies in a cosmological sphere with a volume of ~130^3 (Mpc/h)^3 including supernova feedback, galactic winds, photoheating due to an uniform meta-galactic background and chemical enrichment of the gas and stellar populations. However, we do not consider AGNs. In the simulation, a total of ~20000 galaxies are formed above the resolution limit, and around 60 haloes are more massive than ~10^14 M_sun. Luminosities of the galaxies are calculated based on a stellar population synthesis model including the attenuation by dust, which is calculated from the cold gas left within the simulated galaxies. Environmental effects like colour bi-modality and differential clust...

  19. The SCUBA-2 Cosmology Legacy Survey: The clustering of submillimetre galaxies in the UKIDSS UDS field

    CERN Document Server

    Wilkinson, Aaron; Chen, Chian-Chou; Smail, Ian; Arumugam, Vinodiran; Blain, Andrew; Chapin, Edward L; Chapman, Scott C; Conselice, Christopher J; Cowley, William I; Dunlop, James S; Farrah, Duncan; Geach, James; Hartley, William G; Ivison, Rob J; Maltby, David T; Michałowski, Michał J; Mortlock, Alice; Scott, Douglas; Simpson, Chris; Simpson, James M; van der Werf, Paul; Wild, Vivienne

    2016-01-01

    Submillimetre galaxies (SMGs) are among the most luminous dusty galaxies in the Universe, but their true nature remains unclear; are SMGs the progenitors of the massive elliptical galaxies we see in the local Universe, or are they just a short-lived phase among more typical star-forming galaxies? To explore this problem further, we investigate the clustering of SMGs identified in the SCUBA-2 Cosmology Legacy Survey. We use a catalogue of submillimetre ($850\\mu$m) source identifications derived using a combination of radio counterparts and colour/IR selection to analyse a sample of 914 SMGs in the UKIDSS Ultra Deep Survey (UDS), making this the largest high redshift sample of these galaxies to date. Using angular cross-correlation techniques, we estimate the halo masses for this large sample of SMGs and compare them with passive and star-forming galaxies selected in the same field. We find that SMGs, on average, occupy high-mass dark matter halos (M$_{\\text{halo}} >10^{13}$M$_{\\odot}$) at redshifts $z > 2.5$, ...

  20. A Chandra/ACIS Study of 30 Doradus II. X-ray Point Sources in the Massive Star Cluster R136 and Beyond

    CERN Document Server

    Townsley, L K; Feigelson, E D; Garmire, G P; Getman, K V

    2006-01-01

    We have studied the X-ray point source population of the 30 Doradus star-forming complex in the Large Magellanic Cloud using high-spatial-resolution X-ray images and spatially-resolved spectra obtained with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-ray Observatory. Here we describe the X-ray sources in a 17' x 17' field centered on R136, the massive star cluster at the center of the main 30 Dor nebula. We detect 20 of the 32 Wolf-Rayet stars in the ACIS field. R136 is resolved at the subarcsecond level into almost 100 X-ray sources, including many typical O3--O5 stars as well as a few bright X-ray sources previously reported. Over two orders of magnitude of scatter in L_X is seen among R136 O stars, suggesting that X-ray emission in the most massive stars depends critically on the details of wind properties and binarity of each system, rather than reflecting the widely-reported characteristic value L_X/L_bol ~ 10^{-7}. Such a canonical ratio may exist for single massive stars in R136, ...

  1. Chandra Observation of 3C288 - Reheating the Cool Core of a 3 keV Cluster from a Nuclear Outburst at z = 0.246

    CERN Document Server

    Lal, D V; Forman, W R; Hardcastle, M J; Jones, C; Nulsen, P E J; Evans, D A; Croston, J H; Lee, J C

    2010-01-01

    We present results from a 42 ks Chandra/ACIS-S observation of the transitional FRI/FRII radio galaxy 3C288 at z = 0.246. We detect $\\sim$3 keV gas extending to a radius of $\\sim$0.5 Mpc with a 0.5-2.0 keV luminosity of 6.6 $\\times$ 10$^{43}$ ergs s$^{-1}$, implying that 3C288 lies at the center of a poor cluster. We find multiple surface brightness discontinuities in the gas indicative of either a shock driven by the inflation of the radio lobes or a recent merger event. The temperature across the discontinuities is roughly constant with no signature of a cool core, thus disfavoring either the merger cold-front or sloshing scenarios. We argue therefore that the discontinuities are shocks due to the supersonic inflation of the radio lobes. If they are shocks, the energy of the outburst is $\\sim$10^{60} ergs, or roughly 30% of the thermal energy of the gas within the radius of the shock, assuming that the shocks are part of a front produced by a single outburst. The cooling time of the gas is $\\sim$10^8 yrs, so...

  2. XMM-Newton and Chandra observations of the M31 globular cluster black hole candidate XB135: a heavyweight contender cut down to size

    CERN Document Server

    Barnard, R; Garcia, M R; Kolb, U C; Murray, S S

    2015-01-01

    CXOM31 J004252.030+413107.87 is one of the brightest X-ray sources within the D_25 region of M31, and associated with a globular cluster (GC) known as B135; we therefore call this X-ray source XB135. XB135 is a low mass X-ray binary (LMXB) that apparently exhibited hard state characteristics at 0.3--10 keV luminosities 4--6 E+38 erg/s, and the hard state is only observed below ~10% Eddington. If true, the accretor would be a high mass black hole (BH) (> ~50 M_Sun); such a BH may be formed from direct collapse of a metal-poor, high mass star, and the very low metalicity of B135 (0.015 Z_Sun) makes such a scenario plausible. We have obtained new XMM-Newton and Chandra HRC observations to shed light on the nature of this object. We find from the HRC observation that XB135 is a single point source located close to the center of B135. The new XMM-Newton spectrum is consistent with a rapidly spinning ~10--20 M_Sun BH in the steep power law or thermal dominant state, but inconsistent with the hard state that we prev...

  3. Challenges for Precision Cosmology with X-Ray and Sunyaev-Zeldovich Effect Gas Mass Measurements of Galaxy Clusters

    Science.gov (United States)

    Hallman, Eric J.; Motl, Patrick M.; Burns, Jack O.; Norman, Michael L.

    2006-09-01

    We critically analyze the measurement of galaxy cluster gas masses, which is central to cosmological studies that rely on the galaxy cluster gas mass fraction. Using synthetic observations of numerically simulated clusters viewed through their X-ray emission and thermal Sunyaev-Zeldovich effect (SZE), we reduce the observations to obtain measurements of the cluster gas mass. We quantify the possible sources of uncertainty and systematic bias associated with the common simplifying assumptions used in reducing real cluster observations, including isothermality and hydrostatic equilibrium. We find that intrinsic variations in clusters limit the precision of observational gas mass estimation to ~10% to 1 σ confidence, excluding instrumental effects. Gas mass estimates show surprisingly little trending in the scatter as a function of cluster redshift. For the full cluster sample, methods that use SZE profiles out to roughly the virial radius are the simplest, most accurate, and unbiased way to estimate cluster mass. X-ray methods are systematically more precise mass estimators than are SZE methods if merger and cool-core systems are removed, but slightly overestimate (5%-10%) the cluster gas mass on average. We find that cool-core clusters in our samples are particularly poor candidates for observational mass estimation, even when excluding emission from the core region. The effects of cooling in the cluster gas alter the radial profile of the X-ray and SZE surface brightness even outside the cool-core region. Finally, we find that methods using a universal temperature profile estimate cluster masses to higher precision than those assuming isothermality.

  4. The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Cosmological implications of the Fourier space wedges of the final sample

    CERN Document Server

    Grieb, Jan Niklas; Salazar-Albornoz, Salvador; Scoccimarro, Román; Crocce, Martín; Vecchia, Claudio Dalla; Montesano, Francesco; Gil-Marín, Héctor; Ross, Ashley J; Beutler, Florian; Rodríguez-Torres, Sergio; Chuang, Chia-Hsun; Prada, Francisco; Kitaura, Francisco-Shu; Cuesta, Antonio J; Eisenstein, Daniel J; Percival, Will J; Vargas-Magana, Mariana; Tinker, Jeremy L; Tojeiro, Rita; Brownstein, Joel R; Maraston, Claudia; Nichol, Robert C; Olmstead, Matthew D; Samushia, Lado; Seo, Hee-Jong; Streblyanska, Alina; Zhao, Gong-bo

    2016-01-01

    We extract cosmological information from the anisotropic power spectrum measurements from the recently completed Baryon Oscillation Spectroscopic Survey (BOSS), extending the concept of clustering wedges to Fourier space. Making use of new FFT-based estimators, we measure the power spectrum clustering wedges of the BOSS sample by filtering out the information of Legendre multipoles l > 4. Our modelling of these measurements is based on novel approaches to describe non-linear evolution, bias, and redshift-space distortions, which we test using synthetic catalogues based on large-volume N-body simulations. We are able to include smaller scales than in previous analyses, resulting in tighter cosmological constraints. Using three overlapping redshift bins, we measure the angular diameter distance, the Hubble parameter, and the cosmic growth rate, and explore the cosmological implications of our full shape clustering measurements in combination with CMB and SN Ia data. Assuming a {\\Lambda}CDM cosmology, we constra...

  5. THE ATACAMA COSMOLOGY TELESCOPE: SUNYAEV-ZEL'DOVICH-SELECTED GALAXY CLUSTERS AT 148 GHz IN THE 2008 SURVEY

    International Nuclear Information System (INIS)

    We report on 23 clusters detected blindly as Sunyaev-ZEL'DOVICH (SZ) decrements in a 148 GHz, 455 deg2 map of the southern sky made with data from the Atacama Cosmology Telescope 2008 observing season. All SZ detections announced in this work have confirmed optical counterparts. Ten of the clusters are new discoveries. One newly discovered cluster, ACT-CL J0102-4915, with a redshift of 0.75 (photometric), has an SZ decrement comparable to the most massive systems at lower redshifts. Simulations of the cluster recovery method reproduce the sample purity measured by optical follow-up. In particular, for clusters detected with a signal-to-noise ratio greater than six, simulations are consistent with optical follow-up that demonstrated this subsample is 100% pure. The simulations further imply that the total sample is 80% complete for clusters with mass in excess of 6 x 1014 solar masses referenced to the cluster volume characterized by 500 times the critical density. The Compton y-X-ray luminosity mass comparison for the 11 best-detected clusters visually agrees with both self-similar and non-adiabatic, simulation-derived scaling laws.

  6. DEEP CHANDRA MONITORING OBSERVATIONS OF NGC 4649. II. WIDE-FIELD HUBBLE SPACE TELESCOPE IMAGING OF THE GLOBULAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, MI 48824 (United States); Fabbiano, Giuseppina; Luo, Bin; Kim, Dong-Woo; Fragos, Tassos [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Brodie, Jean P. [UCO/Lick Observatory, 1156 High Street, Santa Cruz, CA 95064 (United States); Gallagher, John S. [Department of Astronomy, University of Wisconsin, Madison, WI 53706-1582 (United States); Kalogera, Vassiliki [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); King, Andrew [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Zezas, Andreas, E-mail: strader@pa.msu.edu [Physics Department, University of Crete, P.O. Box 2208, GR-710 03, Heraklion, Crete (Greece)

    2012-11-20

    We present g and z photometry and size estimates for globular clusters (GCs) in the massive Virgo elliptical NGC 4649 (M60) using a five-pointing Hubble Space Telescope/Advanced Camera for Surveys mosaic. The metal-poor GCs show a monotonic negative metallicity gradient of -0.43 {+-} 0.10 dex per dex in radius over the full radial range of the data, out to {approx}24 kpc. There is evidence for substantial color substructure among the metal-rich GCs. The metal-poor GCs have typical sizes {approx}0.4 pc larger than the metal-rich GCs out to large galactocentric distances ({approx}> 20 kpc), favoring an intrinsic explanation for the size difference rather than projection effects. There is no clear relation between half-light radius and galactocentric distance beyond {approx}15 kpc, suggesting that the sizes of GCs are not generically set by tidal limitation. Finally, we identify {approx}20 candidate ultracompact dwarfs that extend down to surprisingly faint absolute magnitudes (M{sub z} {approx} -8.5), and may bridge the gap between this class and 'extended clusters' in the Local Group. Three of the brighter candidates have published radial velocities and can be confirmed as bona fide ultracompact dwarfs; follow-up spectroscopy will determine the nature of the remainder of the candidates.

  7. The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological implications of the configuration-space clustering wedges

    CERN Document Server

    Sanchez, Ariel G; Crocce, Martin; Grieb, Jan Niklas; Salazar-Albornoz, Salvador; DallaVecchia, Claudio; Lippich, Martha; Beutler, Florian; Brownstein, Joel R; Chuang, Chia-Hsun; Eisenstein, Daniel J; Kitaura, Francisco-Shu; Olmstead, Matthew D; Percival, Will J; Prada, Francisco; Rodriguez-Torres, Sergio; Ross, Ashley J; Samushia, Lado; Seo, Hee-Jong; Tinker, Jeremy; Tojeiro, Rita; Vargas-Magana, Mariana; Wang, Yuting; Zhao, Gong-Bo

    2016-01-01

    We explore the cosmological implications of anisotropic clustering measurements in configuration space of the final galaxy samples from Data Release 12 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We implement a new detailed modelling of the effects of non-linearities, galaxy bias and redshift-space distortions that can be used to extract unbiased cosmological information from our measurements for scales $s \\gtrsim 20\\,h^{-1}{\\rm Mpc}$. We combined the galaxy clustering information from BOSS with the latest cosmic microwave background (CMB) observations and Type Ia supernovae samples and found no significant evidence for a deviation from the $\\Lambda$CDM cosmological model. In particular, these data sets can constrain the dark energy equation of state parameter to $w_{\\rm DE}=-0.996\\pm0.042$ when assumed time-independent, the curvature of the Universe to $\\Omega_{k}=-0.0007\\pm 0.0030$ and the sum of the neutrino masses to $\\sum m_{\

  8. The Atacama Cosmology Telescope: Sunyaev-Zel'dovich selected galaxy clusters at 148 GHz from three seasons of data

    Energy Technology Data Exchange (ETDEWEB)

    Hasselfield, Matthew; Hlozek, Renée [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Hilton, Matt [Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Durban, 4041 (South Africa); Marriage, Tobias A.; Crichton, Devin; Gralla, Megan B. [Dept. of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686 (United States); Addison, Graeme E.; Halpern, Mark [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z4 (Canada); Barrientos, L. Felipe; Dünner, Rolando [Departamento de Astronomía y Astrofísica, Facultad de Física, Pontificía Universidad Católica, Casilla 306, Santiago 22 (Chile); Battaglia, Nicholas [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Battistelli, Elia S. [Department of Physics, University of Rome ' ' La Sapienza' ' , Piazzale Aldo Moro 5, I-00185 Rome (Italy); Bond, J. Richard; Hajian, Amir; Hincks, Adam D. [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON, M5S 3H8 (Canada); Das, Sudeep [High Energy Physics Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, IL 60439 (United States); Devlin, Mark J.; Dicker, Simon R. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Dunkley, Joanna [Department of Astrophysics, Oxford University, Oxford, OX1 3RH (United Kingdom); Fowler, Joseph W., E-mail: mhasse@astro.princeton.edu, E-mail: hiltonm@ukzn.ac.za, E-mail: marriage@pha.jhu.edu [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); and others

    2013-07-01

    We present a catalog of 68 galaxy clusters, of which 19 are new discoveries, detected via the Sunyaev-Zel'dovich effect (SZ) at 148 GHz in the Atacama Cosmology Telescope (ACT) survey on the celestial equator. With this addition, the ACT collaboration has reported a total of 91 optically confirmed, SZ detected clusters. The 504 square degree survey region includes 270 square degrees of overlap with SDSS Stripe 82, permitting the confirmation of SZ cluster candidates in deep archival optical data. The subsample of 48 clusters within Stripe 82 is estimated to be 90% complete for M{sub 500c} > 4.5 × 10{sup 14}M{sub s}un and redshifts 0.15 < z < 0.8. While a full suite of matched filters is used to detect the clusters, the sample is studied further through a ''Profile Based Amplitude Analysis'' using a statistic derived from a single filter at a fixed θ{sub 500} = 5.'9 angular scale. This new approach incorporates the cluster redshift along with prior information on the cluster pressure profile to fix the relationship between the cluster characteristic size (R{sub 500}) and the integrated Compton parameter (Y{sub 500}). We adopt a one-parameter family of ''Universal Pressure Profiles'' (UPP) with associated scaling laws, derived from X-ray measurements of nearby clusters, as a baseline model. Three additional models of cluster physics are used to investigate a range of scaling relations beyond the UPP prescription. Assuming a concordance cosmology, the UPP scalings are found to be nearly identical to an adiabatic model, while a model incorporating non-thermal pressure better matches dynamical mass measurements and masses from the South Pole Telescope. A high signal to noise ratio subsample of 15 ACT clusters with complete optical follow-up is used to obtain cosmological constraints. We demonstrate, using fixed scaling relations, how the constraints depend on the assumed gas model if only SZ measurements are used, and

  9. The Atacama Cosmology Telescope: Sunyaev Zel'dovich Selected Galaxy Clusters at 148 GHz in the 2008 Survey

    CERN Document Server

    Marriage, T A; Ade, P A R; Aguirre, P; Amiri, M; Appel, J W; Barrientos, L F; Battistelli, E S; Bond, J R; Brown, B; Burger, B; Chervenak, J; Das, S; Devlin, M J; Dicker, S R; Doriese, W B; Dunkley, J; Dunner, R; Essinger-Hileman, T; Fisher, R P; Fowler, J W; Hajian, A; Halpern, M; Hasselfield, M; Hern'andez-Monteagudo, C; Hilton, G C; Hilton, M; Hincks, A D; Hlozek, R; Huffenberger, K M; Hughes, D H; Hughes, J P; Infante, L; Irwin, K D; Juin, J B; Kaul, M; Klein, J; Kosowsky, A; Lau, J M; Limon, M; Lin, Y -T; Lupton, R H; Marsden, D; Martocci, K; Mauskopf, P; Menanteau, F; Moodley, K; Moseley, H; Netterfield, C B; Niemack, M D; Nolta, M R; Page, L A; Parker, L; Partridge, B; Quintana, H; Reese, E D; Reid, B; Sehgal, N; Sherwin, B D; Sievers, J; Spergel, D N; Staggs, S T; Swetz, D S; Switzer, E R; Thornton, R; Trac, H; Tucker, C; Warne, R; Wilson, G; Wollack, E; Zhao, Y

    2010-01-01

    We report on twenty-three clusters detected blindly as Sunyaev-Zel'dovich (SZ) decrements in a 148 GHz, 455 square-degree map of the southern sky made with data from the Atacama Cosmology Telescope 2008 observing season. All SZ detections have confirmed optical counterparts. Ten of the clusters are new discoveries. One newly discovered cluster, ACT-CL J0102-4915, with a redshift of 0.75 (photometric), has an SZ decrement comparable to the most massive systems at lower redshifts. Simulations of the cluster recovery method reproduce the sample purity measured by optical follow-up. In particular, for clusters detected with a signal-to-noise ratio greater than six, simulations are consistent with optical follow-up that demonstrated this subsample is 100% pure. The simulations further imply that the total sample is 80% complete for clusters with mass in excess of 6x10^14 solar masses referenced to the cluster volume characterized by five hundred times the critical density. The Compton y -- X-ray luminosity mass co...

  10. The Atacama Cosmology Telescope: Sunyaev-Zel'dovich selected galaxy clusters at 148 GHz from three seasons of data

    International Nuclear Information System (INIS)

    We present a catalog of 68 galaxy clusters, of which 19 are new discoveries, detected via the Sunyaev-Zel'dovich effect (SZ) at 148 GHz in the Atacama Cosmology Telescope (ACT) survey on the celestial equator. With this addition, the ACT collaboration has reported a total of 91 optically confirmed, SZ detected clusters. The 504 square degree survey region includes 270 square degrees of overlap with SDSS Stripe 82, permitting the confirmation of SZ cluster candidates in deep archival optical data. The subsample of 48 clusters within Stripe 82 is estimated to be 90% complete for M500c > 4.5 × 1014Msun and redshifts 0.15 500 = 5.'9 angular scale. This new approach incorporates the cluster redshift along with prior information on the cluster pressure profile to fix the relationship between the cluster characteristic size (R500) and the integrated Compton parameter (Y500). We adopt a one-parameter family of ''Universal Pressure Profiles'' (UPP) with associated scaling laws, derived from X-ray measurements of nearby clusters, as a baseline model. Three additional models of cluster physics are used to investigate a range of scaling relations beyond the UPP prescription. Assuming a concordance cosmology, the UPP scalings are found to be nearly identical to an adiabatic model, while a model incorporating non-thermal pressure better matches dynamical mass measurements and masses from the South Pole Telescope. A high signal to noise ratio subsample of 15 ACT clusters with complete optical follow-up is used to obtain cosmological constraints. We demonstrate, using fixed scaling relations, how the constraints depend on the assumed gas model if only SZ measurements are used, and show that constraints from SZ data are limited by uncertainty in the scaling relation parameters rather than sample size or measurement uncertainty. We next add in seven clusters from the ACT Southern survey, including their dynamical mass measurements, which are based on galaxy velocity dispersions and

  11. Modelling injection and feedback of Cosmic Rays in grid-based cosmological simulations: effects on cluster outskirts

    CERN Document Server

    Vazza, F; Gheller, C; Brunetti, G

    2012-01-01

    We present a numerical scheme, implemented in the cosmological adaptive mesh refinement code ENZO, to model the injection of Cosmic Ray (CR) particles at shocks, their advection and their dynamical feedback on thermal baryonic gas. We give a description of the algorithms and show their tests against analytical and idealized one-dimensional problems. Our implementation is able to track the injection of CR energy, the spatial advection of CR energy and its feedback on the thermal gas in run-time. This method is applied to study CR acceleration and evolution in cosmological volumes, with both fixed and variable mesh resolution. We compare the properties of galaxy clusters with and without CRs, for a sample of high-resolution clusters with different dynamical states. At variance with similar simulations based on Smoothed Particles Hydrodynamics, we report that the inclusion of CR feedback in our method decreases the central gas density in clusters, thus reducing the X-ray and Sunyaev-Zeldovich effect from the clu...

  12. Southern Cosmology Survey II: Massive Optically-Selected Clusters from 70 square degrees of the SZE Common Survey Area

    CERN Document Server

    Menanteau, Felipe; Barrientos, L Felipe; Deshpande, Amruta J; Hilton, Matt; Infante, Leopoldo; Jimenez, Raul; Kosowsky, Arthur; Moodley, Kavilan; Spergel, David; Verde, Licia

    2010-01-01

    We present a catalog of 105 rich and massive ($M>3\\times10^{14}M_{\\sun}$) optically-selected clusters of galaxies extracted from 70 square-degrees of public archival griz imaging from the Blanco 4-m telescope acquired over 45 nights between 2005 and 2007. We use the clusters' optically-derived properties to estimate photometric redshifts, optical luminosities, richness, and masses. We complement the optical measurements with archival XMM-Newton and ROSAT X-ray data which provide additional luminosity and mass constraints on a modest fraction of the cluster sample. Two of our clusters show clear evidence for central lensing arcs; one of these has a spectacular large-diameter, nearly-complete Einstein Ring surrounding the brightest cluster galaxy. A strong motivation for this study is to identify the massive clusters that are expected to display prominent signals from the Sunyaev-Zeldovich Effect (SZE) and therefore be detected in the wide-area mm-band surveys being conducted by both the Atacama Cosmology Teles...

  13. The Impact of Galaxy Cluster Mergers on Cosmological Parameter Estimation from Surveys of the Sunyaev-Zel'dovich Effect

    Science.gov (United States)

    Wik, Daniel R.; Sarazin, Craig L.; Ricker, Paul M.; Randall, Scott W.

    2008-06-01

    Sensitive surveys of the cosmic microwave background will detect thousands of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect. Two SZ observables, the central or maximum and integrated Comptonization parameters ymax and Y, relate in a simple way to the total cluster mass, which allows the construction of mass functions (MFs) that can be used to estimate cosmological parameters such as ΩM, σ8, and the dark energy parameter w. However, clusters form from the mergers of smaller structures, events that can disrupt the equilibrium of intracluster gas on which SZ- M relations rely. From a set of N-body/hydrodynamical simulations of binary cluster mergers, we calculate the evolution of Y and ymax over the course of merger events and find that both parameters are transiently "boosted," primarily during the first core passage. We then use a semianalytic technique developed by Randall et al. to estimate the effect of merger boosts on the distribution functions YF and yF of Y and ymax, respectively, via cluster merger histories determined from extended Press-Schechter (PS) merger trees. We find that boosts do not induce an overall systematic effect on YFs, and the values of ΩM, σ8, and w were returned to within 2% of values expected from the nonboosted YFs. The boosted yFs are significantly biased, however, causing ΩM to be underestimated by 15%-45%, σ8 to be overestimated by 10%-25%, and w to be pushed to more negative values by 25%-45%. We confirm that the integrated SZ effect, Y, is far more robust to mergers than ymax, as previously reported by Motl et al. and similarly found for the X-ray equivalent YX, and we conclude that Y is the superior choice for constraining cosmological parameters.

  14. The Chandra X-Ray Optics

    CERN Document Server

    Weisskopf, Martin C

    2011-01-01

    Significant advances in science always take place when the state of the art in instrumentation improves dramatically. NASA's Chandra X-Ray Observatory represents such an advance. Launched in July of 1999, Chandra is an observatory designed to study the x-ray emission from all categories of astronomical objects --- from comets, planets, and normal stars to quasars, galaxies, and clusters of galaxies. At the heart of this observatory is the precision X-Ray optic that has been vital for Chandra's outstanding success and which features an angular resolution improved by an order of magnitude compared to its forerunners. The Chandra mission is now entering its 13-th year of operation. Given that the Observatory was designed for a minimum of 3 years of operation testifies to its robust and carefully thought out design. We review the design and construction of the remarkable telescope, present examples of its usage for astronomy and astrophysics, and speculate upon the future.

  15. The Atacama Cosmology Telescope: Physical Properties of Sunyaev-Zel'dovich Effect Clusters on the Celestial Equator

    CERN Document Server

    Menanteau, Felipe; Barrientos, L Felipe; Battaglia, Nicholas; Bond, J Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark J; Dünner, Rolando; Gralla, Megan; Hajian, Amir; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D; Hughes, John P; Infante, Leopoldo; Kosowsky, Arthur; Marriage, Tobias A; Marsden, Danica; Moodley, Kavilan; Niemack, Michael D; Nolta, Michael R; Page, Lyman A; Partridge, Bruce; Reese, Erik D; Schmitt, Benjamin L; Sievers, Jon; Spergel, David N; Staggs, Suzanne T; Switzer, Eric; Wollack, Edward J

    2012-01-01

    We present the optical and X-ray properties of 68 galaxy clusters selected via the Sunyaev-Zel'dovich Effect at 148 GHz by the Atacama Cosmology Telescope (ACT). Our sample, from an area of 504 square degrees centered on the celestial equator, is divided into two regions. The main region uses 270 square degrees of the ACT survey that overlaps with the co-added ugriz imaging from the Sloan Digital Sky Survey (SDSS) over Stripe 82 plus additional near-infrared pointed observations with the Apache Point Observatory 3.5-meter telescope. We confirm a total of 49 clusters to z~1.3, of which 22 (all at z>0.55) are new discoveries. For the second region the regular-depth SDSS imaging allows us to confirm 19 more clusters up to z~0.7, of which 10 systems are new. We present the optical richness, photometric redshifts, and separation between the SZ position and the brightest cluster galaxy (BCG). We find no significant offset between the cluster SZ centroid and BCG location and a weak correlation between optical richne...

  16. The Atacama Cosmology Telescope: the stellar content of galaxy clusters selected using the Sunyaev-Zel'dovich effect

    CERN Document Server

    Hilton, Matt; Sifón, Cristóbal; Baker, Andrew J; Barrientos, L Felipe; Battaglia, Nicholas; Bond, J Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark J; Gralla, Megan; Hajian, Amir; Hincks, Adam D; Hughes, John P; Infante, Leopoldo; Irwin, Kent D; Kosowsky, Arthur; Lin, Yen-Ting; Marriage, Tobias A; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D; Nolta, Mike R; Page, Lyman A; Reese, Erik D; Sievers, Jon; Spergel, David N; Wollack, Edward J

    2013-01-01

    We present a first measurement of the stellar mass component of galaxy clusters selected via the Sunyaev-Zel'dovich (SZ) effect, using 3.6 um and 4.5 um photometry from the Spitzer Space Telescope. Our sample consists of 14 clusters detected by the Atacama Cosmology Telescope (ACT), which span the redshift range 0.27 < z < 1.07 (median z = 0.50), and have dynamical mass measurements, accurate to about 30 per cent, with median M500 = 6.9 x 10^{14} MSun. We measure the 3.6 um and 4.5 um galaxy luminosity functions, finding the characteristic magnitude (m*) and faint-end slope (alpha) to be similar to those for IR-selected cluster samples. We perform the first measurements of the scaling of SZ-observables (Y500 and y0) with both brightest cluster galaxy (BCG) stellar mass and total cluster stellar mass (M500star). We find a significant correlation between BCG stellar mass and Y500 (E(z)^{-2/3} DA^2 Y500 ~ M*^{1.2 +/- 0.6}), although we are not able to obtain a strong constraint on the slope of the relation...

  17. The Atacama Cosmology Telescope: Detection or Sunyaev-Zel'Dovich Decrement in Groups and Clusters Associated with Luminous Red Galaxies

    Science.gov (United States)

    Hand, Nick; Appel, John William; Battaglia, Nick; Bond, J. Richard; Das, Sudeep; Devlin, Mark J.; Dunkley, Joanna; Dunner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph W.; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Hughes, John P.; Irwin, Kent D.; Klein, Jeff; Kosowsky, Arthur; Lin, Yen-Ting; Marriage, Tobias A.; Marsden, Danica; McLaren, Mike; Wollack, Ed

    2010-01-01

    We present a detection of the Sunyaev-Zel'dovich (SZ) decrement associated with the Luminous Red Galaxy (LRG) sample of the Sloan Digital Sky Survey. The SZ data come from 148 GHz maps of the equatorial region made by the Atacama Cosmology Telescope (ACT). The LRG sample is divided by luminosity into four bins, and estimates for the central Sunyaev-Zel'dovich temperature decrement are calculated through a stacking process. We detect and account for a bias of the SZ signal due to weak radio sources. We use numerical simulations to relate the observed decrement to Y(sub 200) and clustering properties to relate the galaxy luminosity bins to mass. We also use a relation between BCG luminosity and cluster mass based on stacked gravitational lensing measurements to estimate the characteristic halo masses. The masses are found to be in the range approx.10(exp 13) - 10(exp 14)/h Stellar Mass, a lower range than has been previously probed.

  18. Cosmology from large scale galaxy clustering and galaxy-galaxy lensing with Dark Energy Survey Science Verification data

    CERN Document Server

    Kwan, Juliana; Clampitt, Joseph; Blazek, Jonathan; Crocce, Martin; Jain, Bhuvnesh; Zuntz, Joe; Amara, Adam; Becker, Matthew; Bernstein, Gary; Bonnett, Christopher; DeRose, Joseph; Dodelson, Scott; Eifler, Tim; Gaztanaga, Enrique; Giannantonio, Tommaso; Gruen, Daniel; Hartley, Will; Kacprzak, Tomasz; Kirk, Donnacha; Krause, Elisabeth; MacCrann, Niall; Miquel, Ramon; Park, Youngsoo; Ross, Ashley; Rozo, Eduardo; Rykoff, Eli; Sheldon, Erin; Troxel, Michael A; Wechsler, Risa; Abbott, Tim; Abdalla, Filipe; Allam, Sahar; Benoit-Lévy, Aurélien; Brooks, David; Burke, David; Rosell, Aurelio Carnero; Kind, Matias Carrasco; Cunha, Carlos; D'Andrea, Chris; da Costa, Luiz; Desai, Shantanu; Diehl, H Thomas; Dietrich, Jörg; Doel, Peter; Evrard, August; Fernandez, Enrique; Finley, David; Flaugher, Brenna; Fosalba, Pablo; Frieman, Josh; Gerdes, David; Gruendl, Robert; Gutierrez, Gaston; Honscheid, Klaus; James, David; Jarvis, Mike; Kuehn, Kyler; Lahav, Ofer; Lima, Marcos; Maia, Marcio; Marshall, Jennifer; Martini, Paul; Melchior, Peter; Mohr, Joe; Nichol, Robert; Nord, Brian; Plazas, Andres; Reil, Kevin; Romer, Kathy; Roodman, Aaron; Sanchez, Eusebio; Scarpine, Vic; Sevilla, Ignacio; Smith, R Chris; Soares-Santos, Marcelle; Sobreira, Flavia; Suchyta, Eric; Swanson, Molly; Tarle, Gregory; Thomas, Daniel; Vikram, Vinu; Walker, Alistair

    2016-01-01

    We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as Omega_m = 0.31 +/- 0.09 and the clustering amplitude of the matter power spectrum as sigma_8 = 0.74 +/- 0.13 after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into S_8 = sigma_8(Omega_m/0.3)^{0.16} = 0.74 +/- 0.12 for our fiducial lens redshift bin at 0.35

  19. Chandra Independently Determines Hubble Constant

    Science.gov (United States)

    2006-08-01

    A critically important number that specifies the expansion rate of the Universe, the so-called Hubble constant, has been independently determined using NASA's Chandra X-ray Observatory. This new value matches recent measurements using other methods and extends their validity to greater distances, thus allowing astronomers to probe earlier epochs in the evolution of the Universe. "The reason this result is so significant is that we need the Hubble constant to tell us the size of the Universe, its age, and how much matter it contains," said Max Bonamente from the University of Alabama in Huntsville and NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala., lead author on the paper describing the results. "Astronomers absolutely need to trust this number because we use it for countless calculations." Illustration of Sunyaev-Zeldovich Effect Illustration of Sunyaev-Zeldovich Effect The Hubble constant is calculated by measuring the speed at which objects are moving away from us and dividing by their distance. Most of the previous attempts to determine the Hubble constant have involved using a multi-step, or distance ladder, approach in which the distance to nearby galaxies is used as the basis for determining greater distances. The most common approach has been to use a well-studied type of pulsating star known as a Cepheid variable, in conjunction with more distant supernovae to trace distances across the Universe. Scientists using this method and observations from the Hubble Space Telescope were able to measure the Hubble constant to within 10%. However, only independent checks would give them the confidence they desired, considering that much of our understanding of the Universe hangs in the balance. Chandra X-ray Image of MACS J1149.5+223 Chandra X-ray Image of MACS J1149.5+223 By combining X-ray data from Chandra with radio observations of galaxy clusters, the team determined the distances to 38 galaxy clusters ranging from 1.4 billion to 9.3 billion

  20. The Atacama Cosmology Telescope: Sunyaev-Zel'dovich Selected Galaxy Clusters at 148 GHz from Three Seasons of Data

    CERN Document Server

    Hasselfield, Matthew; Marriage, Tobias A; Addison, Graeme E; Barrientos, L Felipe; Battaglia, Nick; Battistelli, Elia S; Bond, J Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark J; Dicker, Simon R; Dunkley, Joanna; Dunner, Rolando; Fowler, Joseph W; Gralla, Megan B; Hajian, Amir; Halpern, Mark; Hincks, Adam D; Hlozek, Renée; Hughes, John P; Infante, Leopoldo; Irwin, Kent D; Kosowsky, Arthur; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D; Nolta, Michael R; Page, Lyman A; Partridge, Bruce; Reese, Erik D; Schmitt, Benjamin L; Sehgal, Neelima; Sherwin, Blake D; Sievers, Jon; Sifón, Cristóbal; Spergel, David N; Staggs, Suzanne T; Swetz, Daniel S; Switzer, Eric R; Thornton, Robert; Trac, Hy; Wollack, Edward J

    2013-01-01

    [Abridged] We present a catalog of 68 galaxy clusters, of which 19 are new discoveries, detected via the Sunyaev-Zel'dovich effect (SZ) at 148 GHz in the Atacama Cosmology Telescope (ACT) survey of 504 square degrees on the celestial equator. A subsample of 48 clusters within the 270 square degree region overlapping SDSS Stripe 82 is estimated to be 90% complete for M_500c > 4.5e14 Msun and 0.15 < z < 0.8. While matched filters are used to detect the clusters, the sample is studied further through a "Profile Based Amplitude Analysis" using a single filter at a fixed \\theta_500 = 5.9' angular scale. This new approach takes advantage of the "Universal Pressure Profile" (UPP) to break the degeneracy between the cluster extent (R_500) and the integrated Compton parameter (Y_500). The UPP scalings are found to be nearly identical to an adiabatic model, while a model incorporating non-thermal pressure better matches dynamical mass measurements and masses from the South Pole Telescope. A complete, high signal ...

  1. The Atacama Cosmology Telescope: Dynamical Masses for 44 SZ-Selected Galaxy Clusters over 755 Square Degrees

    Science.gov (United States)

    Sifon, Cristobal; Battaglia, Nick; Hasselfield, Matthew; Menanteau, Felipe; Barrientos, L. Felipe; Bond, J. Richard; Crichton, Devin; Devlin, Mark J.; Dunner, Rolando; Hilton, Matt; Wollack, Edward J.

    2016-01-01

    We present galaxy velocity dispersions and dynamical mass estimates for 44 galaxy clusters selected via the Sunyaev-Zeldovich (SZ) effect by the Atacama Cosmology Telescope. Dynamical masses for 18 clusters are reported here for the first time. Using N-body simulations, we model the different observing strategies used to measure the velocity dispersions and account for systematic effects resulting from these strategies. We find that the galaxy velocity distributions may be treated as isotropic, and that an aperture correction of up to 7 per cent in the velocity dispersion is required if the spectroscopic galaxy sample is sufficiently concentrated towards the cluster centre. Accounting for the radial profile of the velocity dispersion in simulations enables consistent dynamical mass estimates regardless of the observing strategy. Cluster masses M200 are in the range (1 - 15) times 10 (sup 14) Solar Masses. Comparing with masses estimated from the SZ distortion assuming a gas pressure profile derived from X-ray observations gives a mean SZ-to-dynamical mass ratio of 1:10 plus or minus 0:13, but there is an additional 0.14 systematic uncertainty due to the unknown velocity bias; the statistical uncertainty is dominated by the scatter in the mass-velocity dispersion scaling relation. This ratio is consistent with previous determinations at these mass scales.

  2. The Atacama Cosmology Telescope: Dynamical masses for 44 SZ-selected galaxy clusters over 755 square degrees

    CERN Document Server

    Sifón, Cristóbal; Menanteau, Felipe; Hasselfield, Matthew; Barrientos, L Felipe; Bond, J Richard; Crichton, Devin; Devlin, Mark J; Dünner, Rolando; Hilton, Matt; Hincks, Adam D; Hlozek, Renée; Huffenberger, Kevin M; Hughes, John P; Infante, Leopoldo; Kosowsky, Arthur; Marsden, Danica; Marriage, Tobias A; Moodley, Kavilan; Niemack, Michael D; Page, Lyman A; Spergel, David N; Staggs, Suzanne T; Trac, Hy; Wollack, Edward J

    2015-01-01

    We present galaxy velocity dispersions and dynamical mass estimates for 44 galaxy clusters selected via the Sunyaev-Zel'dovich (SZ) effect by the Atacama Cosmology Telescope. Dynamical masses for 18 clusters are reported here for the first time. Using N-body simulations, we model the different observing strategies used to measure the velocity dispersions and account for systematic effects resulting from these strategies. We find that the galaxy velocity distributions may be treated as isotropic, and that an aperture correction of up to 7 per cent in the velocity dispersion is required if the spectroscopic galaxy sample is sufficiently concentrated towards the cluster centre. Accounting for the radial profile of the velocity dispersion in simulations enables consistent dynamical mass estimates regardless of the observing strategy. Cluster masses $M_{200}$ are in the range $(1-15)\\times10^{14}M_\\odot$. Comparing with masses estimated from the SZ distortion assuming a gas pressure profile derived from X-ray obse...

  3. The Impact of Galaxy Cluster Mergers on Cosmological Parameter Estimation from Surveys of the Sunyaev-Zel'dovich Effect

    CERN Document Server

    Wik, Daniel R; Ricker, Paul M; Randall, Scott W

    2008-01-01

    Sensitive surveys of the Cosmic Microwave Background will detect thousands of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect. Two SZ observables, the central or maximum and integrated Comptonization parameters y_max and Y, relate in a simple way to the total cluster mass, which allow the construction of mass functions (MFs) that can be used to estimate cosmological parameters such as Omega_M, sigma_8, and the dark energy parameter w. However, clusters form from the mergers of smaller structures, events that can disrupt the equilibrium of intracluster gas upon which SZ-M relations rely. From a set of N-body/hydrodynamical simulations of binary cluster mergers, we calculate the evolution of Y and y_max over the course of merger events and find that both parameters are transiently "boosted," primarily during the first core passage. We then use a semi-analytic technique developed by Randall et al. (2002) to estimate the effect of merger boosts on the distribution functions YF and yF of Y and y_max, respec...

  4. Chandra Opens New Line of Investigation on Dark Energy

    Science.gov (United States)

    2004-05-01

    Astronomers have detected and probed dark energy by applying a powerful, new method that uses images of galaxy clusters made by NASA's Chandra X-ray Observatory. The results trace the transition of the expansion of the Universe from a decelerating to an accelerating phase several billion years ago, and give intriguing clues about the nature of dark energy and the fate of the Universe. "Dark energy is perhaps the biggest mystery in physics," said Steve Allen of the Institute of Astronomy (IoA) at the University of Cambridge in England, and leader of the study. "As such, it is extremely important to make an independent test of its existence and properties." Abell 2029 Chandra X-ray Image of Abell 2029 Allen and his colleagues used Chandra to study 26 clusters of galaxies at distances corresponding to light travel times of between one and eight billion years. These data span the time when the Universe slowed from its original expansion, before speeding up again because of the repulsive effect of dark energy. "We're directly seeing that the expansion of the Universe is accelerating by measuring the distances to these galaxy clusters," said Andy Fabian also of the IoA, a co-author on the study. The new Chandra results suggest that the dark energy density does not change quickly with time and may even be constant, consistent with the "cosmological constant" concept first introduced by Albert Einstein. If so, the Universe is expected to continue expanding forever, so that in many billions of years only a tiny fraction of the known galaxies will be observable. More Animations Animation of the "Big Rip" If the dark energy density is constant, more dramatic fates for the Universe would be avoided. These include the "Big Rip," where dark energy increases until galaxies, stars, planets and eventually atoms are eventually torn apart. The "Big Crunch," where the Universe eventually collapses on itself, would also be ruled out. Chandra's probe of dark energy relies on the unique

  5. Galaxy Cluster Astrophysics and Cosmology: Questions and Opportunities for the Coming Decade

    CERN Document Server

    Myers, S T; Aguirre, J; Bond, J R; Burns, J O; Clarke, T; Devlin, M; Evrard, A; Golwala, S; Habib, S; Heitmann, K; Holzapfel, W L; Kassim, N E; Kravtsov, A; Lee, A T; Markevich, M; Marrone, D; Nagai, D; Page, L; Pierpaoli, E; Rudnick, L; Sievers, J; Taylor, G; Voit, Mark

    2009-01-01

    We are learning much about how structure forms, in particular how clusters as nodes in the cosmic web evolve and accrete matter, and about the physical processes within these objects. In the next decade, the study of clusters will enable us to tackle important questions regarding the nature of Dark Matter and Dark Energy, how clusters co-evolve with super-massive black holes at their centers, and to advance our knowledge about fundamental plasma astrophysics. This science white paper outlines the key questions and research opportunities in cluster astrophysics that are emerging in the coming decade and beyond, and serves as an overview to other cluster related white papers.

  6. Beyond Chandra - the X-ray Surveyor

    CERN Document Server

    Weisskopf, Martin C; Tananbaum, Harvey; Vikhlinin, Alexey

    2015-01-01

    Over the past 16 years, NASA's Chandra X-ray Observatory has provided an unparalleled means for exploring the universe with its half-arcsecond angular resolution. Chandra studies have deepened our understanding of galaxy clusters, active galactic nuclei, galaxies, supernova remnants, planets, and solar system objects addressing almost all areas of current interest in astronomy and astrophysics. As we look beyond Chandra, it is clear that comparable or even better angular resolution with greatly increased photon throughput is essential to address even more demanding science questions, such as the formation and subsequent growth of black hole seeds at very high redshift; the emergence of the first galaxy groups; and details of feedback over a large range of scales from galaxies to galaxy clusters. Recently, NASA Marshall Space Flight Center, together with the Smithsonian Astrophysical Observatory, has initiated a concept study for such a mission named the X-ray Surveyor. This study starts with a baseline payloa...

  7. Iterative Maps with Hierarchical Clustering for the Observed Scales of Astrophysical and Cosmological Structures

    OpenAIRE

    Capozziello, S.; Martino, S; De Siena, S.; Guerra, F.; Illuminati, F.

    2000-01-01

    We derive, in order of magnitude, the observed astrophysical and cosmological scales in the Universe, from neutron stars to superclusters of galaxies, up to, asymptotically, the observed radius of the Universe. This result is obtained by introducing a recursive scheme of alternating hierachical mechanisms of three-dimensional and two-dimensional close packings of gravitationally interacting objects. The iterative scheme yields a rapidly converging geometric sequence, which can be described as...

  8. \\Omega_0 and \\lambda_0 from galaxy and quasar clustering: cosmic virial theorem and cosmological redshift-space distortion

    OpenAIRE

    Suto, Yasushi

    1996-01-01

    I discuss two cosmological tests to determine the cosmological density parameter \\Omega_0 the cosmological constant \\lambda_0, which make use of the anisotropy of the two-point correlation functions due to the peculiar velocity field and the cosmological redshift-space distortion.

  9. An Extensive Census of Hubble Space Telescope Counterparts to Chandra X-Ray Sources in the Globular Cluster 47 Tucanae. II. Time Series and Analysis

    Science.gov (United States)

    Edmonds, Peter D.; Gilliland, Ronald L.; Heinke, Craig O.; Grindlay, Jonathan E.

    2003-10-01

    We report time series and variability information for the optical identifications of X-ray sources in 47 Tucanae reported in Paper I (at least 22 cataclysmic variables [CVs] and 29 active binaries). The radial distribution of the CVs is indistinguishable from that of the millisecond pulsars (MSPs) detected by Freire et al. A study of the eight CVs with secure orbital periods (two obtained from the Chandra study of Grindlay et al.) shows that the 47 Tuc CVs have fainter accretion disks, in the V band, than field CVs with similar periods. These faint disks and the faint absolute magnitudes (MV) of the 47 Tuc CVs suggests they have low accretion rates. One possible explanation is that the 47 Tuc objects may be a more representative sample of CVs, down to our detection threshold, than the CVs found in the field (where many low accretion rate systems are believed to be undiscovered), showing the advantages of deep globular cluster observations. The median FX/Fopt value for the 47 Tuc CVs is higher than that of all known classes of field CV, partly because of the faint MV values and partly because of the relatively high X-ray luminosities (LX). The latter are only seen in DQ Her systems in the field, but the 47 Tuc CVs are much fainter optically than most field DQ Her's. Previous work by Edmonds et al. has shown that the four brightest CVs in NGC 6397 have optical spectra and broadband colors that are consistent with DQ Her's having lower than average accretion rates. Some combination of magnetic behavior and low accretion rates may be able to explain our observations, but the results at present are ambiguous, since no class of field CV has distributions of both LX and MV that are consistent with those of the 47 Tuc CVs. The radial distribution of the X-ray detected active binaries is indistinguishable from that of the much larger sample of optical variables (eclipsing and contact binaries and BY Dra variables) detected in previous Wide Field Planetary Camera 2 (WFPC2

  10. A measurement of large-scale peculiar velocities of clusters of galaxies: results and cosmological implications

    CERN Document Server

    Kashlinsky, A; Kocevski, D; Ebeling, H

    2008-01-01

    Peculiar velocities of clusters of galaxies can be measured by studying the fluctuations in the cosmic microwave background (CMB) generated by the scattering of the microwave photons by the hot X-ray emitting gas inside clusters. While for individual clusters such measurements result in large errors, a large statistical sample of clusters allows one to study cumulative quantities dominated by the overall bulk flow of the sample with the statistical errors integrating down. We present results from such a measurement using the largest all-sky X-ray cluster catalog combined to date and the 3-year WMAP CMB data. We find a strong and coherent bulk flow on scales out to at least > 300 h^{-1} Mpc, the limit of our catalog. This flow is difficult to explain by gravitational evolution within the framework of the concordance LCDM model and may be indicative of the tilt exerted across the entire current horizon by far-away pre-inflationary inhomogeneities.

  11. The dynamical state of the galaxy cluster: Theoretical insights from cosmological simulations

    CERN Document Server

    Cui, Weiguang; Borgani, Stefano; Knebe, Alexander; Lewis, Geraint F; Murante, Giuseppe; Poole, Greg B

    2016-01-01

    Following the work of Cui et al. (2016b, hereafter Paper I), we investigate the dynamical state of the galaxy clusters from the theoretical point of view. After extending to vrial radius $R_{vir}$, we reselect out 123 clusters with $\\log(M_{DM, vir}) \\le 14.5$ from the galaxy cluster samples in Paper I, here DM indicate the dark-matter-only run. These clusters from the two hydro-dynamical runs are matched to the dark-matter-only run using the unique dark matter particle ID. We investigate 4 independent parameters, which are normally used to classify the cluster dynamical state. We find that the virial ratio $\\eta$ from both hydro-dynamical runs is $\\sim$ 10 per cent lower than from the dark-matter-only run; there is no clear bimodal distribution between the relaxed and un-relaxed clusters for all investigated parameters. Further, using the velocity dispersion deviation parameter $\\zeta$ , which is defined as the ratio between cluster velocity dispersion $\\sigma$ and the theoretical prediction $\\sigma_t = \\sqr...

  12. Gravitational Clustering in Redshift Space: Non-Gaussian Tail of the Cosmological Density Distribution Function

    CERN Document Server

    Bagla, J S; Ray, Suryadeep

    2006-01-01

    We study the non-Gaussian tail of the probability distribution function of density in cosmological N-Body simulations for a variety of initial conditions. We compare the behaviour of the non-Gaussian tail in the real space with that in the redshift space. The form of the PDF in redshift space is of great significance as galaxy surveys probe this and not the real space analogue predicted using theoretical models. We model the non-Gaussian tail using the halo model. In the weakly non-linear regime the moments of counts in cells in the redshift space approach the values expected from perturbation theory for moments in real space. We show that redshift space distortions in the non-linear regime dominate over signatures of initial conditions or the cosmological background. We illustrate this using Skewness and higher moments of counts in cells, as well as using the form of the non-Gaussian tail of the distribution function. We find that at scales smaller than the scale of non-linearity the differences in Skewness,...

  13. The cluster-galaxy cross-spectrum: an additional probe of cosmological and halo parameters

    CERN Document Server

    Huetsi, Gert

    2008-01-01

    There are several wide field galaxy and cluster surveys planned for the nearest future, e.g. BOSS, WFMOS, ADEPT, Hetdex, SPT, eROSITA. In the simplest approach one would analyze these independently, thus neglecting the extra information provided by the cluster-galaxy cross-pairs. In this paper we have focused on the possible synergy between these surveys by investigating the amount of information encoded in the cross-pairs. We present a model for the cluster-galaxy cross-spectrum within the Halo Model framework. To assess the gain in performance due to inclusion of the cluster-galaxy cross-pairs we carry out a Fisher matrix analysis for a BOSS-like galaxy redshift survey targeting luminous red galaxies and a hypothetical mass-limited cluster redshift survey with a lower mass threshold of 1.7x10^14 M_sun/h over the same volume. On small scales cluster-galaxy cross-spectrum probes directly density profile of the halos, instead of the density profile convolved with itself, as is the case for the galaxy power spe...

  14. Subaru weak-lensing measurement of a z = 0.81 cluster discovered by the Atacama Cosmology Telescope Survey

    CERN Document Server

    Miyatake, Hironao; Takada, Masahiro; Mandelbaum, Rachel; Mineo, Sogo; Aihara, Hiroaki; Spergel, David N; Bickerton, Steven J; Bond, J Richard; Hajian, Amir; Hilton, Matt; Hincks, Adam D; Hughes, John P; Infante, Leopoldo; Lin, Yen-Ting; Lupton, Robert H; Marriage, Tobias A; Marsden, Danica; Menanteau, Felipe; Miyazaki, Satoshi; Moodley, Kavilan; Niemack, Michael D; Oguri, Masamune; Price, Paul A; Reese, Erik D; Sifon, Cristobal; Wollack, Edward J; Yasuda, Naoki

    2013-01-01

    We present a Subaru weak lensing measurement of ACT-CL J0022.2-0036, one of the most luminous, high-redshift (z=0.81) Sunyaev-Zel'dovich (SZ) clusters discovered in the 268 deg^2 equatorial region survey of the Atacama Cosmology Telescope. For the weak lensing analysis using i'-band images, we use a model-fitting (Gauss-Laguerre shapelet) method to measure shapes of galaxy images, where we fit galaxy images in different exposures simultaneously to obtain best-fit ellipticities taking into account the different PSFs in each exposure. We also take into account the astrometric distortion effect on galaxy images by performing the model fitting in the world coordinate system. To select background galaxies behind the cluster at z=0.81, we use photometric redshift (photo-z) estimates for every galaxy derived from the co-added images of multi-passband Br'i'z'Y, with PSF matching/homogenization. After a photo-z cut for background galaxy selection, we detect the tangential weak lensing distortion signal with a total si...

  15. A Measurement of Large-Scale Peculiar Velocities of Clusters of Galaxies: Results and Cosmological Implications

    Science.gov (United States)

    Kashlinsky, A.; Atrio-Barandela, F.; Kocevski, D.; Ebeling, H.

    2008-10-01

    Peculiar velocities of clusters of galaxies can be measured by studying the fluctuations in the cosmic microwave background (CMB) generated by the scattering of the microwave photons by the hot X-ray-emitting gas inside clusters. While for individual clusters such measurements result in large errors, a large statistical sample of clusters allows one to study cumulative quantities dominated by the overall bulk flow of the sample with the statistical errors integrating down. We present results from such a measurement using the largest all-sky X-ray cluster catalog combined to date and the 3 yr WMAP CMB data. We find a strong and coherent bulk flow on scales out to at least gsim300 h-1 Mpc, the limit of our catalog. This flow is difficult to explain by gravitational evolution within the framework of the concordance ΛCDM model and may be indicative of the tilt exerted across the entire current horizon by far-away pre-inflationary inhomogeneities.

  16. Cluster Radio Halos at the crossroads between astrophysics and cosmology in the SKA era

    CERN Document Server

    Cassano, R; Brunetti, G; Brüggen, M; Clarke, T; Dallacasa, D; Dolag, K; Ettori, S; Giacintucci, S; Giocoli, C; Gitti, M; Johnston-Hollitt, M; Kale, R; Markevitch, M; Norris, R; Pandey-Pommier, M; Pratt, G W; Röttgering, H; Venturi, T

    2014-01-01

    Giant Radio Halos (RH) are diffuse, Mpc-sized, synchrotron radio sources observed in a fraction of merging galaxy clusters. The current scenario for the origin of RHs assumes that turbulence generated during cluster mergers re-accelerates pre-existing fossil and/or secondary electrons in the intra-cluster-medium (ICM) to the energies necessary to produce the observed radio emission. Moreover, more relaxed clusters could host diffuse "off state" halos produced by secondary electrons. In this Chapter we use Monte Carlo simulations, that combine turbulent-acceleration physics and the generation of secondaries in the ICM, to calculate the occurrence of RHs in the Universe, their spectral properties and connection with properties of the hosting clusters. Predictions for SKA1 surveys are presented at low (100-300 MHz) and mid (1-2 GHz) frequencies assuming the expected sensitivities and spatial resolutions of SKA1. SKA1 will step into an unexplored territory allowing us to study the formation and evolution of RHs i...

  17. The XMM-LSS cluster sample and its cosmological applications. Prospects for the XMM next decade

    CERN Document Server

    Pierre, M; Melin, J B; consortium, the XMM-LSS

    2007-01-01

    The well defined selection function of the XMM-LSS survey enables a simultaneous modelling of the observed cluster number counts and of the evolution of the L-T relation. We present results pertaining to the first 5 deg2 for a well controlled sample comprising 30 objects: they are compatible with the WMAP3 parameter set along with cluster self-similar evolution. Extending such a survey to 200 deg2 would (1) allow discriminating between the major scenarios of the cluster L-T evolution and (2) provide a unique self-sufficient determination of sigma8 and Gamma with an accuracy of ~ 5% and 10% respectively, when adding mass information from weak lensing and S-Z observations.

  18. NASA's Chandra Finds Black Holes Are "Green"

    Science.gov (United States)

    2006-04-01

    Black holes are the most fuel efficient engines in the Universe, according to a new study using NASA's Chandra X-ray Observatory. By making the first direct estimate of how efficient or "green" black holes are, this work gives insight into how black holes generate energy and affect their environment. The new Chandra finding shows that most of the energy released by matter falling toward a supermassive black hole is in the form of high-energy jets traveling at near the speed of light away from the black hole. This is an important step in understanding how such jets can be launched from magnetized disks of gas near the event horizon of a black hole. Illustration of Fuel for a Black Hole Engine Illustration of Fuel for a Black Hole Engine "Just as with cars, it's critical to know the fuel efficiency of black holes," said lead author Steve Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, and the Stanford Linear Accelerator Center. "Without this information, we cannot figure out what is going on under the hood, so to speak, or what the engine can do." Allen and his team used Chandra to study nine supermassive black holes at the centers of elliptical galaxies. These black holes are relatively old and generate much less radiation than quasars, rapidly growing supermassive black holes seen in the early Universe. The surprise came when the Chandra results showed that these "quiet" black holes are all producing much more energy in jets of high-energy particles than in visible light or X-rays. These jets create huge bubbles, or cavities, in the hot gas in the galaxies. Animation of Black Hole in Elliptical Galaxy Animation of Black Hole in Elliptical Galaxy The efficiency of the black hole energy-production was calculated in two steps: first Chandra images of the inner regions of the galaxies were used to estimate how much fuel is available for the black hole; then Chandra images were used to estimate the power required to produce

  19. Clustering, Cosmology and a New Era of Black Hole Demographics - I. The Conditional Luminosity Function of Active Galactic Nuclei

    Science.gov (United States)

    Ballantyne, D. R.

    2016-09-01

    Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z ˜ 5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, this paper presents a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function - all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z ≈ 0 and 0.9 using the limited data that is currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z ≈ 0.9 quasars may be commonly hosted by haloes with Mh ˜ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGNs of different luminosities in cosmological simulations.

  20. A New Independent Limit on the Cosmological Constant/Dark Energy from the Relativistic Bending of Light by Galaxies and Clusters of Galaxies

    CERN Document Server

    Ishak, Mustapha; Dossett, Jason; Moldenhauer, Jacob; Allison, Chris

    2007-01-01

    We derive new limits on the value of the cosmological constant, $\\Lambda$, based on the Einstein bending of light by systems where the lens is a distant galaxy or a cluster of galaxies. We use an amended lens equation in which the contribution of $\\Lambda$ to the Einstein deflection angle is taken into account and use observations of Einstein radii around several lens systems. Interestingly, we find that the contribution of the cosmological constant to the bending angle can be as big as 27% of the magnitude of the first-order term in the deflection angle and a few orders of magnitude larger than the second-order term. We use these observations of bending-angles to derive limits on the value of $\\Lambda$ and find them to be competitive with the value determined from cosmology.

  1. The extended ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey (REFLEX II) IV. X-ray Luminosity Function and First Constraints on Cosmological Parameters

    CERN Document Server

    Böhringer, H; Collins, C A

    2014-01-01

    The X-ray luminosity function is an important statistic of the census of galaxy clusters and an important means to probe the cosmological model of our Universe. Based on our recently completed REFLEX II cluster sample we construct the X-ray luminosity function of galaxy clusters for several redshift slices from $z = 0$ to $z = 0.4$ and discuss its implications. We find no significant signature of redshift evolution of the luminosity function in the redshift interval. We provide the results of fits of a parameterized Schechter function and extensions of it which provide a reasonable characterization of the data. Using a model for structure formation and galaxy cluster evolution we compare the observed X-ray luminosity function with predictions for different cosmological models. For the most interesting constraints for the cosmological parameters $\\Omega_m$ and $\\sigma_8$ we obatain $\\Omega_m \\sim 0.27 \\pm 0.03$ and $\\sigma_8 \\sim 0.80 \\pm 0.03$ based on the statistical uncertainty alone. Marginalizing over the...

  2. The SCUBA-2 cosmology legacy survey: Ultraluminous star-forming galaxies in a z = 1.6 cluster

    International Nuclear Information System (INIS)

    We analyze new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z = 1.62 cluster, Cl 0218.3–0510, which lies in the UKIRT Infrared Deep Sky Survey/Ultra-Deep Survey field of the SCUBA-2 Cosmology Legacy Survey. Combining these tracers of obscured star-formation activity with the extensive photometric and spectroscopic information available for this field, we identify 31 far-infrared/submillimeter-detected probable cluster members with bolometric luminosities ≳1012 L ☉ and show that by virtue of their dust content and activity, these represent some of the reddest and brightest galaxies in this structure. We exploit ALMA submillimeter continuum observations, which cover one of these sources, to confirm the identification of a SCUBA-2-detected ultraluminous star-forming galaxy in this structure. Integrating the total star-formation activity in the central region of the structure, we estimate that it is an order of magnitude higher (in a mass-normalized sense) than clusters at z ∼ 0.5-1. However, we also find that the most active cluster members do not reside in the densest regions of the structure, which instead host a population of passive and massive, red galaxies. We suggest that while the passive and active populations have comparable near-infrared luminosities at z = 1.6, MH ∼ –23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present day that are less luminous than the descendants of those galaxies that were already passive at z ∼ 1.6 (MH ∼ –20.5 and MH ∼ –21.5, respectively, at z ∼ 0). We conclude that the massive galaxy population in the dense cores of present-day clusters were already in place at z = 1.6 and that in Cl 0218.3–0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure.

  3. Cosmological Simulations of the Preheating Scenario for Galaxy Cluster Formation: Comparison to Analytic Models and Observations

    CERN Document Server

    Younger, Joshua D

    2007-01-01

    We perform a set of non--radiative cosmological simulations of a preheated intracluster medium in which the entropy of the gas was uniformly boosted at high redshift. The results of these simulations are used first to test the current analytic techniques of preheating via entropy input in the smooth accretion limit. When the unmodified profile is taken directly from simulations, we find that this model is in excellent agreement with the results of our simulations. This suggests that preheated efficiently smoothes the accreted gas, and therefore a shift in the unmodified profile is a good approximation even with a realistic accretion history. When we examine the simulation results in detail, we do not find strong evidence for entropy amplification, at least for the high-redshift preheating model adopted here. In the second section of the paper, we compare the results of the preheating simulations to recent observations. We show -- in agreement with previous work -- that for a reasonable amount of preheating, a...

  4. Mass Calibration and Cosmological Analysis of the SPT-SZ Galaxy Cluster Sample Using Velocity Dispersion $\\sigma_v$ and X-ray $Y_\\textrm{X}$ Measurements

    CERN Document Server

    Bocquet, S; Mohr, J J; Aird, K A; Ashby, M L N; Bautz, M; Bayliss, M; Bazin, G; Benson, B A; Bleem, L E; Brodwin, M; Carlstrom, J E; Chang, C L; Chiu, I; Cho, H M; Clocchiatti, A; Crawford, T M; Crites, A T; Desai, S; de Haan, T; Dietrich, J P; Dobbs, M A; Foley, R J; Forman, W R; Gangkofner, D; George, E M; Gladders, M D; Gonzalez, A H; Halverson, N W; Hennig, C; Hlavacek-Larrondo, J; Holder, G P; Holzapfel, W L; Hrubes, J D; Jones, C; Keisler, R; Knox, L; Lee, A T; Leitch, E M; Liu, J; Lueker, M; Luong-Van, D; Marrone, D P; McDonald, M; McMahon, J J; Meyer, S S; Mocanu, L; Murray, S S; Padin, S; Pryke, C; Reichardt, C L; Rest, A; Ruel, J; Ruhl, J E; Saliwanchik, B R; Sayre, J T; Schaffer, K K; Shirokoff, E; Spieler, H G; Stalder, B; Stanford, S A; Staniszewski, Z; Stark, A A; Story, K; Stubbs, C W; Vanderlinde, K; Vieira, J D; Vikhlinin, A; Williamson, R; Zahn, O; Zenteno, A

    2014-01-01

    We present a velocity dispersion-based mass calibration of the South Pole Telescope Sunyaev-Zel'dovich effect survey (SPT-SZ) galaxy cluster sample. Using a homogeneously selected sample of 100 cluster candidates from 720 deg2 of the survey along with 63 velocity dispersion ($\\sigma_v$) and 16 X-ray Yx measurements of sample clusters, we simultaneously calibrate the mass-observable relation and constrain cosmological parameters. The calibrations using $\\sigma_v$ and Yx are consistent at the $0.6\\sigma$ level, with the $\\sigma_v$ calibration preferring ~16% higher masses. We use the full cluster dataset to measure $\\sigma_8(\\Omega_ m/0.27)^{0.3}=0.809\\pm0.036$. The SPT cluster abundance is lower than preferred by either the WMAP9 or Planck+WMAP9 polarization (WP) data, but assuming the sum of the neutrino masses is $\\sum m_\

  5. The effects of assembly bias on cosmological inference from galaxy-galaxy lensing and galaxy clusters

    CERN Document Server

    McEwen, Joseph E

    2016-01-01

    The combination of galaxy-galaxy lensing (GGL) and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modeling can extend the approach down to nonlinear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with large scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older halos affects the cutoff of the mean occupation function $\\langle N_\\text{cen}(M_\\text{min}) \\rangle$ for central galaxies, with halos in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We intro...

  6. Weak-lensing mass calibration of the Atacama Cosmology Telescope equatorial Sunyaev-Zeldovich cluster sample with the Canada-France-Hawaii telescope stripe 82 survey

    Science.gov (United States)

    Battaglia, N.; Leauthaud, A.; Miyatake, H.; Hasselfield, M.; Gralla, M. B.; Allison, R.; Bond, J. R.; Calabrese, E.; Crichton, D.; Devlin, M. J.; Dunkley, J.; Dünner, R.; Erben, T.; Ferrara, S.; Halpern, M.; Hilton, M.; Hill, J. C.; Hincks, A. D.; Hložek, R.; Huffenberger, K. M.; Hughes, J. P.; Kneib, J. P.; Kosowsky, A.; Makler, M.; Marriage, T. A.; Menanteau, F.; Miller, L.; Moodley, K.; Moraes, B.; Niemack, M. D.; Page, L.; Shan, H.; Sehgal, N.; Sherwin, B. D.; Sievers, J. L.; Sifón, C.; Spergel, D. N.; Staggs, S. T.; Taylor, J. E.; Thornton, R.; van Waerbeke, L.; Wollack, E. J.

    2016-08-01

    Mass calibration uncertainty is the largest systematic effect for using clusters of galaxies to constrain cosmological parameters. We present weak lensing mass measurements from the Canada-France-Hawaii Telescope Stripe 82 Survey for galaxy clusters selected through their high signal-to-noise thermal Sunyaev-Zeldovich (tSZ) signal measured with the Atacama Cosmology Telescope (ACT). For a sample of 9 ACT clusters with a tSZ signal-to-noise greater than five the average weak lensing mass is (4.8±0.8) ×1014 Msolar, consistent with the tSZ mass estimate of (4.70±1.0) ×1014 Msolar which assumes a universal pressure profile for the cluster gas. Our results are consistent with previous weak-lensing measurements of tSZ-detected clusters from the Planck satellite. When comparing our results, we estimate the Eddington bias correction for the sample intersection of Planck and weak-lensing clusters which was previously excluded.

  7. Iterative Maps with Hierarchical Clustering for the Observed Scales of Astrophysical and Cosmological Structures

    CERN Document Server

    Capozziello, S; De Siena, S; Guerra, F; Illuminati, F

    2000-01-01

    We derive, in order of magnitude, the observed astrophysical and cosmologicalscales in the Universe, from neutron stars to superclusters of galaxies, up to,asymptotically, the observed radius of the Universe. This result is obtained byintroducing a recursive scheme of alternating hierachical mechanisms ofthree-dimensional and two-dimensional close packings of gravitationallyinteracting objects. The iterative scheme yields a rapidly converging geometricsequence, which can be described as a hierarchical clustering of aggregates,having the observed radius of the Universe as its fixed point.

  8. nIFTy Cosmology: Galaxy/halo mock catalogue comparison project on clustering statistics

    CERN Document Server

    Chuang, Chia-Hsun; Prada, Francisco; Munari, Emiliano; Avila, Santiago; Izard, Albert; Kitaura, Francisco-Shu; Manera, Marc; Monaco, Pierluigi; Murray, Steven; Knebe, Alexander; Scoccola, Claudia G; Yepes, Gustavo; Garcia-Bellido, Juan; Marin, Felipe A; Muller, Volker; Skibba, Ramin; Crocce, Martin; Fosalba, Pablo; Gottlober, Stefan; Klypin, Anatoly A; Power, Chris; Tao, Charling; Turchaninov, Victor

    2014-01-01

    We present a comparison of major methodologies of fast generating mock halo or galaxy catalogues. The comparison is done for two-point and the three-point clustering statistics. The reference catalogues are drawn from the BigMultiDark N-body simulation. Both friend-of-friends (including distinct halos only) and spherical overdensity (including distinct halos and subhalos) catalogs have been used with the typical number density of a large-volume galaxy surveys. We demonstrate that a proper biasing model is essential for reproducing the power spectrum at quasilinear and even smaller scales. With respect to various clustering statistics a methodology based on perturbation theory and a realistic biasing model leads to very good agreement with N-body simulations. However, for the quadrupole of the correlation function or the power spectrum, only the method based on semi-N-body simulation could reach high accuracy (1% level) at small scales, i.e., r0.15 h/Mpc. For those methods that only produce distinct haloes, a ...

  9. Weak-Lensing Mass Calibration of the Atacama Cosmology Telescope Equatorial Sunyaev-Zeldovich Cluster Sample with the Canada-France-Hawaii Telescope Stripe 82 Survey

    CERN Document Server

    Battaglia, N; Miyatake, H; Hasselfield, M; Gralla, M B; Allison, R; Bond, J R; Calabrese, E; Crichton, D; Devlin, M J; Dunkley, J; Dünner, R; Erben, T; Ferrara, S; Halpern, M; Hilton, M; Hill, J C; Hincks, A D; Hložek, R; Huffenberger, K M; Hughes, J P; Kneib, J P; Kosowsky, A; Makler, M; Marriage, T A; Menanteau, F; Miller, L; Moodley, K; Moraes, B; Niemack, M D; Page, L; Shan, H; Sehgal, N; Sherwin, B D; Sievers, J L; Sifón, C; Spergel, D N; Staggs, S T; Taylor, J; Thornton, R; van Waerbeke, L; Wollack, E J

    2015-01-01

    Mass calibration uncertainty is the largest systematic effect for using clusters of galaxies to constrain cosmological parameters. We present weak lensing mass measurements from the Canada-France-Hawaii Telescope Stripe 82 Survey for galaxy clusters selected through their high signal-to-noise thermal Sunyaev-Zeldovich (tSZ) signal measured with the Atacama Cosmology Telescope (ACT). The average weak lensing mass is $\\left(4.8\\pm0.8\\right)\\,\\times10^{14}\\,\\mathrm{M}_\\odot$, consistent with the tSZ mass estimate of $\\left(4.70\\pm1.0\\right)\\,\\times10^{14}\\,\\mathrm{M}_\\odot$ which assumes a universal pressure profile for the cluster gas. Our results are consistent with previous weak-lensing measurements of tSZ-detected clusters from the Planck satellite. When comparing our results, we estimate the Eddington bias correction for the sample intersection of Planck and weak-lensing clusters which was previously neglected.

  10. A cosmological view of extreme mass-ratio inspirals in nuclear star clusters

    CERN Document Server

    Mapelli, M; Vecchio, A; Graham, Alister W; Gualandris, A

    2012-01-01

    There is increasing evidence that many galaxies host both a nuclear star cluster (NC) and a super-massive black hole (SMBH). Their coexistence is particularly prevalent in spheroids with stellar mass 10^8-10^10 solar masses. We study the possibility that a stellar-mass black hole (BH) hosted by a NC inspirals and merges with the central SMBH. Due to the high stellar density in NCs, extreme mass-ratio inspirals (EMRIs) of BHs onto SMBHs in NCs may be important sources of gravitational waves (GWs). We consider sensitivity curves for three different space-based GW laser interferometric mission concepts: the Laser Interferometer Space Antenna (LISA), the New Gravitational wave Observatory (NGO) and the DECi-hertz Interferometer Gravitational wave Observatory (DECIGO). We predict that, under the most optimistic assumptions, LISA and DECIGO will detect up to thousands of EMRIs in NCs per year, while NGO will observe up to tens of EMRIs per year. We explore how a number of factors may affect the predicted rates. In ...

  11. Cosmological Effects of Powerful AGN Outbursts in Galaxy Clusters: Insights from an XMM-Newton Observation of MS 0735+7421

    Science.gov (United States)

    Gitti, M.; McNamara, B. R.; Nulsen, P. E. J.; Wise, M. W.

    2007-01-01

    We report on the results of an analysis o f XMM-Newton observations o f MS 0735+7421, the galaxy cluster that hosts the most energetic AGN outburst currently known. .The previous chandra image shows twin giant x-ray cavities (approx.200 kpc diameter) filled with radio emission and surrounded by a weak shock front. XMM data are consistent with these findings. The total energy in cavities and shock (1E62 erg(approx.100 kpc), to heat the gas within 1 Mpc by approx.1/4 kev per particle. The cluster exhibits an upward departure (factor approx.2) from the mean L-T relation. The boost in emissivity produced by the ICM compression in the bright shells due to the cavity expansion may contribute to explain the high luminosity and high central gas mass fraction that we measure. The scaled temperature and metallicity profiles are in general agreement with those observed in re1axed clusters. Also, the quantities we measure are consistent with the observed M-T relation. We conclude that violent outbursts such as the one in MS 0735+7421 do not cause dramatic scaling relations (other than the L-T relation). However, if they are relatively common they may play a role in creating the global cluster properties.

  12. The Chandra Source Catalog: Processing and Infrastructure

    Science.gov (United States)

    Evans, Janet; Evans, Ian N.; Glotfelty, Kenny J.; Hain, Roger; Hall, Diane M.; Miller, Joseph B.; Plummer, David A.; Zografou, Panagoula; Primini, Francis A.; Anderson, Craig S.; Bonaventura, Nina R.; Chen, Judy C.; Davis, John E.; Doe, Stephen M.; Fabbiano, Giuseppina; Galle, Elizabeth C.; Gibbs, Danny G., II; Grier, John D.; Harbo, Peter N.; He, Xiang Qun (Helen); Houck, John C.; Karovska, Margarita; Kashyap, Vinay L.; Lauer, Jennifer; McCollough, Michael L.; McDowell, Jonathan C.; Mitschang, Arik W.; Morgan, Douglas L.; Mossman, Amy E.; Nichols, Joy S.; Nowak, Michael A.; Refsdal, Brian L.; Rots, Arnold H.; Siemiginowska, Aneta L.; Sundheim, Beth A.; Tibbetts, Michael S.; van Stone, David W.; Winkelman, Sherry L.

    2009-09-01

    Chandra Source Catalog processing recalibrates each observation using the latest available calibration data, and employs a wavelet-based source detection algorithm to identify all the X-ray sources in the field of view. Source properties are then extracted from each detected source that is a candidate for inclusion in the catalog. Catalog processing is completed by matching sources across multiple observations, merging common detections, and applying quality assurance checks. The Chandra Source Catalog processing system shares a common processing infrastructure and utilizes much of the functionality that is built into the Standard Data Processing (SDP) pipeline system that provides calibrated Chandra data to end-users. Other key components of the catalog processing system have been assembled from the portable CIAO data analysis package. Minimal new software tool development has been required to support the science algorithms needed for catalog production. Since processing pipelines must be instantiated for each detected source, the number of pipelines that are run during catalog construction is a factor of order 100 times larger than for SDP. The increased computational load, and inherent parallel nature of the processing, is handled by distributing the workload across a multi-node Beowulf cluster. Modifications to the SDP automated processing application to support catalog processing, and extensions to Chandra Data Archive software to ingest and retrieve catalog products, complete the upgrades to the infrastructure to support catalog processing.

  13. The First Chandra Field

    Energy Technology Data Exchange (ETDEWEB)

    Weisskopf, Martin C.; /NASA, Marshall; Aldcroft, Thomas L.; /Harvard-Smithsonian Ctr. Astrophys.; Cameron, Robert A.; /Harvard-Smithsonian Ctr. Astrophys. /SLAC; Gandhi,; Foellmi, Cedric; /European Southern Obs., Chile; Elsner, Ronald F.; /NASA, Marshall; Patel, Sandeep K.; /USRA, Huntsville; Wu, Kinwah; /Mullard Space Sci. Lab.; O' Dell, Stephen; /NASA, Marshall

    2005-09-09

    Before the official first-light images, the Chandra X-ray Observatory obtained an X-ray image of the field to which its focal plane was first exposed. We describe this historic observation and report our study of the first Chandra field. Chandra's Advanced CCD Imaging Spectrometer (ACIS) detected 15 X-ray sources, the brightest being dubbed ''Leon X-1'' to honor the Chandra Telescope Scientist, Leon Van Speybroeck. Based upon our analysis of the X-ray data and spectroscopy at the European Southern Observatory (ESO; La Silla, Chile), we find that Leon X-1 is a Type-1 (unobscured) active galactic nucleus (AGN) at a redshift z = 0.3207. Leon X-1 exhibits strong Fe II emission and a broad-line Balmer decrement that is unusually flat for an AGN. Within the context of the Eigenvector-1 correlation space, these properties suggest that Leon X-1 may be a massive ({ge} 10{sup 9} M{sub {circle_dot}}) black hole, accreting at a rate approaching its Eddington limit.

  14. Cosmological constraints from the cluster contribution to the power spectrum of the soft X-ray background. New evidence for a low sigma_8

    CERN Document Server

    Diego-Rodriguez, J M; Silk, J; Barcons, X; Voges, W

    2003-01-01

    We use the X-ray power spectrum of the ROSAT all-sky survey in the R6 band (approximately 0.9-1.3 keV) to set an upper limit on the galaxy cluster power spectrum. The cluster power spectrum is modelled with a minimum number of robust assumptions regarding the structure of the clusters. The power spectrum of ROSAT sets an upper limit on the Omega_m-sigma_8 plane which excludes all the models with sigma_8 above sigma_8 = 0.5/(Omega_m^0.38) in a flat LCDM universe. We discuss the possible sources of systematic errors in our conclusions, mainly dominated by the assumed L_x-T relation. Alternatively, this relation could be constrained by using the X-ray power spectrum, if the cosmological model is known. Our conclusions suggest that only models with a low value of sigma_8 (sigma_8 < 0.8 for Omega_m = 0.3) may be compatible with our upper limit. We also find that models predicting lower luminosities in galaxy clusters are favoured. Reconciling our cosmological constraints with these arising by other methods migh...

  15. ON THE CLUSTER PHYSICS OF SUNYAEV-ZEL'DOVICH AND X-RAY SURVEYS. III. MEASUREMENT BIASES AND COSMOLOGICAL EVOLUTION OF GAS AND STELLAR MASS FRACTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Battaglia, N. [Department of Physics, McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213 (United States); Bond, J. R. [Canadian Institute for Theoretical Astrophysics, 60 St George, Toronto ON, M5S 3H8 (Canada); Pfrommer, C. [Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany); Sievers, J. L., E-mail: christoph.pfrommer@h-its.org [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States)

    2013-11-10

    Gas masses tightly correlate with the virial masses of galaxy clusters, allowing for a precise determination of cosmological parameters by means of X-ray surveys. However, the gas mass fractions (f{sub gas}) at the virial radius (R{sub 200}) derived from recent Suzaku observations are considerably larger than the cosmic mean, calling into question the accuracy of cosmological parameters. Here, we use a large suite of cosmological hydrodynamical simulations to study measurement biases of f{sub gas}. We employ different variants of simulated physics, including radiative gas physics, star formation, and thermal feedback by active galactic nuclei, which we show is able to arrest overcooling and to result in constant stellar mass fractions for redshifts z < 1. Computing the mass profiles in 48 angular cones, we find anisotropic gas and total mass distributions that imply an angular variance of f{sub gas} at the level of 30%. This anisotropy originates from the recent formation epoch of clusters and from the strong internal baryon-to-dark-matter density bias. In the most extreme cones, f{sub gas} can be biased high by a factor of two at R{sub 200} in massive clusters (M{sub 200} ∼ 10{sup 15} M{sub ☉}), thereby providing an explanation for high f{sub gas} measurements by Suzaku. While projection lowers this factor, there are other measurement biases that may (partially) compensate. At R{sub 200}, f{sub gas} is biased high by 20% when assuming hydrostatic equilibrium masses, i.e., neglecting the kinetic pressure, and by another ∼10%-20% due to the presence of density clumping. At larger radii, both measurement biases increase dramatically. While the cluster sample variance of the true f{sub gas} decreases to a level of 5% at R{sub 200}, the sample variance that includes both measurement biases remains fairly constant at the level of 10%-20%. The constant redshift evolution of f{sub gas} within R{sub 500} for massive clusters is encouraging for using gas masses to

  16. Chandra hardware and systems: keeping things running

    Science.gov (United States)

    Paton, Lisa

    2006-06-01

    System management for any organization can be a challenge, but satellite projects present their own issues. I will be presenting the network and system architecture chosen to support the scientists in the Chandra X-ray Center. My group provides the infrastructure for science data processing, mission planning, user support, archive support and software development. Our challenge is to create a stable environment with enough flexibility to roll with the changes during the mission. I'll discuss system and network choices, web service, backups, security and systems monitoring. Also, how to build infrastructure that's flexible, how to support a large group of scientists with a relatively small staff, what challenges we faced (anticipated and unanticipated) and what lessons we learned over the past 6 years since the launch of Chandra. Finally I'll outline our plans for the future including beowulf cluster support, an improved helpdesk system, methods for dealing with the explosive amount of data that needs to be managed.

  17. LoCuSS: Testing hydrostatic equilibrium in galaxy clusters

    Science.gov (United States)

    Smith, G. P.; Mazzotta, P.; Okabe, N.; Ziparo, F.; Mulroy, S. L.; Babul, A.; Finoguenov, A.; McCarthy, I. G.; Lieu, M.; Bahé, Y. M.; Bourdin, H.; Evrard, A. E.; Futamase, T.; Haines, C. P.; Jauzac, M.; Marrone, D. P.; Martino, R.; May, P. E.; Taylor, J. E.; Umetsu, K.

    2016-02-01

    We test the assumption of hydrostatic equilibrium in an X-ray luminosity selected sample of 50 galaxy clusters at 0.15 sub-4 per cent, and our hydrostatic measurements of the same achieve excellent agreement between XMM-Newton and Chandra. The mean ratio of X-ray to lensing mass for these 50 clusters is β_X= 0.95± 0.05, and for the 44 clusters also detected by Planck, the mean ratio of Planck mass estimate to LoCuSS lensing mass is β_P= 0.95± 0.04. Based on a careful like-for-like analysis, we find that LoCuSS, the Canadian Cluster Comparison Project, and Weighing the Giants agree on β_P ≃ 0.9-0.95 at 0.15 Planck cosmology results from the cosmic microwave background and galaxy cluster counts.

  18. Morphology parameters: substructure identification in X-ray galaxy clusters

    CERN Document Server

    Parekh, Viral; Ferrari, Chiara; Angus, Garry; Holwerda, Benne

    2014-01-01

    In recent years multi-wavelength observations have shown the presence of substructures related to merging events in a high fraction of galaxy clusters. Clusters can be roughly grouped into two categories -- relaxed and non-relaxed -- and a proper characterisation of the dynamical state of these systems is of crucial importance both for astrophysical and cosmological studies. In this paper we investigate the use of a number of morphological parameters (Gini, $M_{20}$, Concentration, Asymmetry, Smoothness, Ellipticity and Gini of the second order moment, $G_{M}$) introduced to automatically classify clusters as relaxed or dynamically disturbed systems. We apply our method to a sample of clusters at different redshifts extracted from the {\\it Chandra} archive and we investigate possible correlations between morphological parameters and other X-ray gas properties. We conclude that a combination of the adopted parameters is a very useful tool to properly characterise the X-ray cluster morphology. According to our ...

  19. The Evolution of Structure in X-ray Clusters of Galaxies

    CERN Document Server

    Jeltema, T E; Bautz, M W; Buote, D A; Jeltema, Tesla E.; Canizares, Claude R.; Bautz, Mark W.; Buote, David A.

    2005-01-01

    Using Chandra archival data, we quantify the evolution of cluster morphology with redshift. Clusters form and grow through mergers with other clusters and groups, and the amount of substructure in clusters in the present epoch and how quickly it evolves with redshift depend on the underlying cosmology. Our sample includes 40 X-ray selected, luminous clusters from the Chandra archive, and we quantify cluster morphology using the power ratio method (Buote & Tsai 1995). The power ratios are constructed from the moments of the X-ray surface brightness and are related to a cluster's dynamical state. We find that, as expected qualitatively from hierarchical models of structure formation, high-redshift clusters have more substructure and are dynamically more active than low-redshift clusters. Specifically, the clusters with z>0.5 have significantly higher average third and fourth order power ratios than the lower redshift clusters. Of the power ratios, $P_3/P_0$ is the most unambiguous indicator of an asymmetric...

  20. Chandra Catches Cannibal Galaxy in the Act

    Science.gov (United States)

    2000-07-01

    NASA's Chandra X-ray Observatory image of Perseus A provides new insight into how this supergiant galaxy has grown by cannibalizing other galaxies and gas in the vicinity. For the first time astronomers see an X-ray shadow cast by a smaller galaxy as its gas is being stripped away by the enormous galaxy. The research was reported by Professor Andrew Fabian of the Institute of Astronomy, Cambridge, England on June 7 at the 196th National Meeting of the American Astronomical Society, in Rochester, NY. Other members of the research team are Jeremy Sanders, Stefano Ettori, Steve Allen, Carolin Crawford, Kazushi Iwasawa, and Roderick Johnstone of the Institute of Astronomy, Gregory Taylor on the National Radio Astronomy Observatory, Socorro, NM, and Patrick Ogle of the Massachusetts Institute of Technology, Cambridge, MA. Perseus A, or NGC 1275, is in the center of a large galaxy cluster 320 million light years from Earth. The cluster, which contains thousands of galaxies and enough gas to make thousands more, is one of the largest gravitationally bound objects in the universe. Over the eons, Perseus A has accumulated hundreds of billions of stars to become one of the most massive known galaxies as gas and galaxies have been pulled inward by gravity. The Chandra observation shows a region of hot gas that extends over several hundred thousand light years. The gas in the outer portion of the cluster has a temperature of 70 million degrees. The cluster gas cools gradually and settles toward the center of the cluster. A galaxy with "only" about 20 billion stars is falling into Perseus A (located at two o'clock from the center of the image) and appears as a small dark patch due to absorption of X rays by cool gas in the infalling galaxy. Another larger hole seen further out is thought to be due to a bubble of high-energy particles ejected in an explosion from Perseus A hundreds of millions of years ago. These outbursts are presumably fueled by matter releasing tremendous

  1. Probing dark energy via galaxy cluster outskirts

    CERN Document Server

    Morandi, Andrea

    2016-01-01

    We present a Bayesian approach to combine $Planck$ data and the X-ray physical properties of the intracluster medium in the virialization region of a sample of 320 galaxy clusters ($0.056 3$ keV) observed with $Chandra$. We exploited the high-level of similarity of the emission measure in the cluster outskirts as cosmology proxy. The cosmological parameters are thus constrained assuming that the emission measure profiles at different redshift are weakly self-similar, that is their shape is universal, explicitly allowing for temperature and redshift dependency of the gas fraction. This cosmological test, in combination with $Planck$+SNIa data, allows us to put a tight constraint on the dark energy models. For a constant-$w$ model, we have $w=-1.010\\pm0.030$ and $\\Omega_m=0.311\\pm0.014$, while for a time-evolving equation of state of dark energy $w(z)$ we have $\\Omega_m=0.308\\pm 0.017$, $w_0=-0.993\\pm0.046$ and $w_a=-0.123\\pm0.400$. Constraints on the cosmology are further improved by adding priors on the gas f...

  2. Higher-Order Calculations of Light Deflection and the Contribution of the Cosmological Constant to Einstein Radii around Clusters of Galaxies

    Science.gov (United States)

    Dossett, Jason; Ishak, M.; Rindler, W.; Moldenhauer, J.; Allison, C.

    2008-05-01

    Recently, Rindler and Ishak (2007) made a breakthrough in the field of gravitational lensing showing that a cosmological constant, Λ, will indeed contribute to the bending angle of light by a concentric mass, in fact, by decreasing it. Then Ishak et al. (2007) showed that the effect can be applied to observations of Einstein radii around clusters of galaxies. We present here various higher-order calculations and results for the bending angle and the Lambda contribution. Surprisingly, we find that the Lambda term is the next largest term after the Einstein first-order term for many cluster lens systems. For those lens systems, the Lambda contribution is larger than the second-order term and may be the next targeted term by future high precision experiments.

  3. The BMW-Chandra Serendipitous Source Catalog

    Science.gov (United States)

    Romano, P.; Campana, S.; Mignani, R. P.; Moretti, A.; Mottini, M.; Panzera, M. R.; Tagliaferri, G.

    2004-08-01

    We present the BMW-Chandra source catalog drawn from all Chandra ACIS-I pointed observations with an exposure time in excess of 10 ks public as of March 2003 (136 observations). Using the wavelet detection algorithm developed by Lazzati et al. (1999) and Campana et al. (1999), which can characterize point-like as well as extended sources, we identified 21325 sources. Among them, 16758 are serendipitous, i.e. not associated with the targets of the pointings, and do not require a non-automated analysis. This makes our catalog the largest compilation of Chandra sources to date. The 0.5--10 keV absorption corrected fluxes of these sources range from ˜ 3× 10-16 to 9×10-12 erg cm-2 s-1 with a median of 7× 10-15 erg cm-2 s-1. The catalog consists of count rates and relative errors in three energy bands (total, 0.5--7 keV; soft, 0.5--2 keV; and hard band, 2--7 keV), and source positions relative to the highest signal-to-noise detection among the three bands. The wavelet algorithm also provides an estimate of the extension of the source which we refined with a σ -clipping method. We report on the main properties of the sources in our catalog, such as sky coverage ( ˜ 8 deg2 at a limiting flux of ˜ 10-13 erg cm-2 s-1) and cosmological log N--log S for a subset at high Galactic latitude (∣ b ∣ > 20o) for a flux as low as ˜ 1.5 × 10-15 erg cm-2 s-1. Support for this work was provided by the Italian MIUR.

  4. Lunar Prospecting With Chandra

    Science.gov (United States)

    2003-09-01

    Observations of the bright side of the Moon with NASA's Chandra X-ray Observatory have detected oxygen, magnesium, aluminum and silicon over a large area of the lunar surface. The abundance and distribution of those elements will help to determine how the Moon was formed. "We see X-rays from these elements directly, independent of assumptions about the mineralogy and other complications," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., at a press conference at the "Four Years with Chandra" symposium in Huntsville, Alabama. "We have Moon samples from the six widely-space Apollo landing sites, but remote sensing with Chandra can cover a much wider area," continued Drake. "It's the next best thing to being there, and it's very fast and cost-effective." The lunar X-rays are caused by fluorescence, a process similar to the way that light is produced in fluorescent lamps. Solar X-rays bombard the surface of the Moon, knock electrons out of the inner parts of the atoms, putting them in a highly unstable state. Almost immediately, other electrons rush to fill the gaps, and in the process convert their energy into the fluorescent X-rays seen by Chandra. According to the currently popular "giant impact" theory for the formation of the Moon, a body about the size of Mars collided with the Earth about 4.5 billion years ago. This impact flung molten debris from the mantle of both the Earth and the impactor into orbit around the Earth. Over the course of tens of millions of years, the debris stuck together to form the Moon. By measuring the amounts of aluminum and other elements over a wide area of the Moon and comparing them to the Earth's mantle, Drake and his colleagues plan to help test the giant impact hypothesis. "One early result," quipped Drake, "is that there is no evidence for large amounts of calcium, so cheese is not a major constituent of the Moon." Illustration of Earth's Geocorona Illustration of Earth's Geocorona The same

  5. Deep Chandra, HST-COS, and Megacam Observations of the Phoenix Cluster: Extreme Star Formation and AGN Feedback on Hundred Kiloparsec Scales

    CERN Document Server

    McDonald, M; van Weeren, R J; Applegate, D E; Bayliss, M; Bautz, M W; Benson, B A; Carlstrom, J E; Bleem, L E; Chatzikos, M; Edge, A C; Fabian, A C; Garmire, G P; Hlavacek-Larrondo, J; Jones-Forman, C; Mantz, A B; Miller, E D; Stalder, B; Veilleux, S; Zuhone, J A

    2015-01-01

    We present new ultraviolet, optical, and X-ray data on the Phoenix galaxy cluster (SPT-CLJ2344-4243). Deep optical imaging reveals previously-undetected filaments of star formation, extending to radii of ~50-100 kpc in multiple directions. Combined UV-optical spectroscopy of the central galaxy reveals a massive (2x10^9 Msun)), young (~4.5 Myr) population of stars, consistent with a time-averaged star formation rate of 610 +/- 50 Msun/yr. We report a strong detection of OVI(1032,1038) which appears to originate primarily in shock-heated gas, but may contain a substantial contribution (>1000 Msun/yr) from the cooling intracluster medium. We confirm the presence of deep X-ray cavities in the inner ~10 kpc, which are amongst the most extreme examples of radio-mode feedback detected to date, implying jet powers of 2-7 x10^45 erg/s. We provide evidence that the AGN inflating these cavities may have only recently transitioned from "quasar-mode" to "radio-mode", and may currently be insufficient to completely offset ...

  6. The Atacama Cosmology Telescope: Dynamical Masses and Scaling Relations for a Sample of Massive Sunyaev-Zel'dovich Effect Selected Galaxy Clusters

    CERN Document Server

    Sifon, Cristobal; Hasselfield, Matthew; Marriage, Tobias A; Hughes, John P; Barrientos, L Felipe; Gonzalez, Jorge; Infante, Leopoldo; Addison, Graeme E; Baker, Andrew J; Battaglia, Nick; Bond, J Richard; Das, Sudeep; Devlin, Mark J; Dunkley, Joanna; Dunner, Rolando; Gralla, Megan B; Hajian, Amir; Hilton, Matt; Hincks, Adam D; Kosowsky, Arthur B; Marsden, Danica; Moodley, Kavilan; Niemack, Michael D; Nolta, Michael R; Page, Lyman A; Partridge, Bruce; Reese, Erik D; Sehgal, Neelima; Sievers, Jon; Spergel, David N; Staggs, Suzanne T; Thornton, Robert J; Trac, Hy; Wollack, Edward

    2012-01-01

    We present the first dynamical mass estimates and scaling relations for a sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample consists of 16 massive clusters detected with the Atacama Cosmology Telescope (ACT) over a 455 sq deg. area of the southern sky. Deep multi-object spectroscopic observations were taken to secure intermediate-resolution (R~700-800) spectra and redshifts for ~60 member galaxies on average per cluster. The dynamical masses M_200c of the clusters have been calculated using simulation-based scaling relations between velocity dispersion and mass. The sample has a median redshift z=0.50 and a median mass M_200c=11x10^14 Msun/h_70 with a lower limit M_200c ~ 5x10^14 Msun/h_70, consistent with the expectations for the ACT southern sky survey. These masses are compared to the ACT SZE properties of the sample, specifically, the central SZE amplitude y0, the Compton signal within a 0.5' pixel y_0.5', and the integrated Compton signal Y_200c, which we use to derive SZE-Ma...

  7. THE ATACAMA COSMOLOGY TELESCOPE: DYNAMICAL MASSES AND SCALING RELATIONS FOR A SAMPLE OF MASSIVE SUNYAEV-ZEL'DOVICH EFFECT SELECTED GALAXY CLUSTERS {sup ,}

    Energy Technology Data Exchange (ETDEWEB)

    Sifon, Cristobal; Barrientos, L. Felipe; Gonzalez, Jorge; Infante, Leopoldo; Duenner, Rolando [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Menanteau, Felipe; Hughes, John P.; Baker, Andrew J. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Hasselfield, Matthew [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Marriage, Tobias A.; Crichton, Devin; Gralla, Megan B. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218-2686 (United States); Addison, Graeme E.; Dunkley, Joanna [Sub-department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Battaglia, Nick; Bond, J. Richard; Hajian, Amir [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Das, Sudeep [Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States); Devlin, Mark J. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Hilton, Matt [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); and others

    2013-07-20

    We present the first dynamical mass estimates and scaling relations for a sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample consists of 16 massive clusters detected with the Atacama Cosmology Telescope (ACT) over a 455 deg{sup 2} area of the southern sky. Deep multi-object spectroscopic observations were taken to secure intermediate-resolution (R {approx} 700-800) spectra and redshifts for Almost-Equal-To 60 member galaxies on average per cluster. The dynamical masses M{sub 200c} of the clusters have been calculated using simulation-based scaling relations between velocity dispersion and mass. The sample has a median redshift z = 0.50 and a median mass M{sub 200c}{approx_equal}12 Multiplication-Sign 10{sup 14} h{sub 70}{sup -1} M{sub sun} with a lower limit M{sub 200c}{approx_equal}6 Multiplication-Sign 10{sup 14} h{sub 70}{sup -1} M{sub sun}, consistent with the expectations for the ACT southern sky survey. These masses are compared to the ACT SZE properties of the sample, specifically, the match-filtered central SZE amplitude y{sub 0}-tilde, the central Compton parameter y{sub 0}, and the integrated Compton signal Y{sub 200c}, which we use to derive SZE-mass scaling relations. All SZE estimators correlate with dynamical mass with low intrinsic scatter ({approx}< 20%), in agreement with numerical simulations. We explore the effects of various systematic effects on these scaling relations, including the correlation between observables and the influence of dynamically disturbed clusters. Using the three-dimensional information available, we divide the sample into relaxed and disturbed clusters and find that {approx}50% of the clusters are disturbed. There are hints that disturbed systems might bias the scaling relations, but given the current sample sizes, these differences are not significant; further studies including more clusters are required to assess the impact of these clusters on the scaling relations.

  8. Gravitational clustering of galaxies: Derivation of two-point galaxy correlation function using statistical mechanics of cosmological many-body problem

    Science.gov (United States)

    Ahmad, Farooq; Malik, Manzoor A.; Bhat, M. Maqbool

    2016-07-01

    We derive the spatial pair correlation function in gravitational clustering for extended structure of galaxies (e.g. galaxies with halos) by using statistical mechanics of cosmological many-body problem. Our results indicate that in the limit of point masses (ɛ=0) the two-point correlation function varies as inverse square of relative separation of two galaxies. The effect of softening parameter `ɛ' on the pair correlation function is also studied and results indicate that two-point correlation function is affected by the softening parameter when the distance between galaxies is small. However, for larger distance between galaxies, the two-point correlation function is not affected at all. The correlation length r0 derived by our method depends on the random dispersion velocities functions and we apply our results to obtain the correlation length r0 for such systems which again agrees with the data of N-body simulations and observations.

  9. The abundance and colours of galaxies in high-redshift clusters in the cold dark matter cosmology

    Science.gov (United States)

    Merson, Alexander I.; Baugh, Carlton M.; Gonzalez-Perez, Violeta; Abdalla, Filipe B.; Lagos, Claudia del P.; Mei, Simona

    2016-02-01

    High-redshift galaxy clusters allow us to examine galaxy formation in extreme environments. Here we compile data for 15 z > 1 galaxy clusters to test the predictions from a state-of-the-art semi-analytical model of galaxy formation. The model gives a good match to the slope and zero-point of the cluster red sequence. The model is able to match the cluster galaxy luminosity function at faint and bright magnitudes, but underestimates the number of galaxies around the break in the cluster luminosity function. We find that simply assuming a weaker dust attenuation improves the model predictions for the cluster galaxy luminosity function, but worsens the predictions for the red sequence at bright magnitudes. Examination of the properties of the bright cluster galaxies suggests that the default dust attenuation is large due to these galaxies having large reservoirs of cold gas as well as small radii. We find that matching the luminosity function and colours of high-redshift cluster galaxies, whilst remaining consistent with local observations, poses a challenge for galaxy formation models.

  10. The Chandra HelpDesk

    Science.gov (United States)

    Galle, Elizabeth C.

    2008-03-01

    The Chandra X-ray Center (CXC) HelpDesk has answered hundreds of user questions over the course of the Chandra mission, ranging from basic syntax errors to advanced analysis questions. This talk gives an introduction to the HelpDesk system and staff, presents a sample of recent HelpDesk requests, and discusses how user-submitted questions improve the software and documentation.

  11. Discrete Newtonian Cosmology

    CERN Document Server

    Gibbons, Gary W

    2013-01-01

    In this paper we lay down the foundations for a purely Newtonian theory of cosmology, valid at scales small compared with the Hubble radius, using only Newtonian point particles acted on by gravity and a possible cosmological term. We describe the cosmological background which is given by an exact solution of the equations of motion in which the particles expand homothetically with their comoving positions constituting a central configuration. We point out, using previous work, that an important class of central configurations are homogeneous and isotropic, thus justifying the usual assumptions of elementary treatments. The scale factor is shown to satisfy the standard Raychaudhuri and Friedmann equations without making any fluid dynamic or continuum approximations. Since we make no commitment as to the identity of the point particles, our results are valid for cold dark matter, galaxies, or clusters of galaxies. In future publications we plan to discuss perturbations of our cosmological background from the p...

  12. Predicting Chandra CCD Degradation with the Chandra Radiation Model

    Science.gov (United States)

    Minow, Joseph I.; Blackwell, William C.; DePasquale, Joseph M.; Grant, Catherine E.; O'Dell, Stephen L.; Plucinsky, Paul P.; Schwartz, Daniel A.; Spitzbart, Bradley D.; Wolk, Scott J.

    2008-01-01

    Not long after launch of the Chandra X-Ray Observatory, it was discovered that the Advanced CCD Imaging Spectrometer (ACIS) detector was rapidly degrading due to radiation. Analysis by Chandra personnel showed that this degradation was due to 10w energy protons (100 - 200 keV) that scattered down the optical path onto the focal plane. In response to this unexpected problem, the Chandra Team developed a radiation-protection program that has been used to manage the radiation damage to the CCDs. This program consists of multiple approaches - scheduled sating of the ACIS detector from the radiation environment during passage through radiation belts, real-time monitoring of space weather conditions, on-board monitoring of radiation environment levels, and the creation of a radiation environment model for use in computing proton flux and fluence at energies that damage the ACIS detector. This radiation mitigation program has been very successful. The initial precipitous increase in the CCDs' charge transfer inefficiency (CTI) resulting from proton damage has been slowed dramatically, with the front-illuminated CCDS having an increase in CTI of only 2.3% per year, allowing the ASIS detector's expected lifetime to exceed requirements. This paper concentrates on one aspect of the Chandra radiation mitigation program, the creation of the Chandra Radiation Model (CRM). Because of Chandra's highly elliptical orbit, the spacecraft spends most of its time outside of the trapped radiation belts that present the severest risks to the ACIS detector. However, there is still a proton flux environment that must be accounted for in all parts of Chandra's orbit. At the time of Chandra's launch there was no engineering model of the radiation environment that could be used in the outer regions of the spacecraft's orbit, so the CRM was developed to provide the flux environment of 100 - 200 keV protons in the outer magnetosphere, magnetosheath, and solar wind regions of geospace. This

  13. Clustering, Cosmology and a New Era of Black Hole Demographics -- I. The Conditional Luminosity Function of Active Galactic Nuclei

    CERN Document Server

    Ballantyne, D R

    2016-01-01

    Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to $z \\sim 5$. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, this paper presents a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific $z$. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function -- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method ...

  14. The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological analysis of the DR12 galaxy sample

    CERN Document Server

    Alam, Shadab; Bailey, Stephen; Beutler, Florian; Bizyaev, Dmitry; Blazek, Jonathan A; Bolton, Adam S; Brownstein, Joel R; Burden, Angela; Chuang, Chia-Hsun; Comparat, Johan; Cuesta, Antonio J; Dawson, Kyle S; Eisenstein, Daniel J; Escoffier, Stephanie; Gil-Marín, Héctor; Grieb, Jan Niklas; Hand, Nick; Ho, Shirley; Kinemuchi, Karen; Kirkby, David; Kitaura, Francisco; Malanushenko, Elena; Malanushenko, Viktor; Maraston, Claudia; McBride, Cameron K; Nichol, Robert C; Olmstead, Matthew D; Oravetz, Daniel; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pellejero-Ibanez, Marcos; Percival, Will J; Petitjean, Patrick; Prada, Francisco; Price-Whelan, Adrian M; Reid, Beth A; Rodríguez-Torres, Sergio A; Roe, Natalie A; Ross, Ashley J; Ross, Nicholas P; Rossi, Graziano; Rubiño-Martín, Jose Alberto; Sánchez, Ariel G; Saito, Shun; Salazar-Albornoz, Salvador; Samushia, Lado; Satpathy, Siddharth; Scóccola, Claudia G; Schlegel, David J; Schneider, Donald P; Seo, Hee-Jong; Simmons, Audrey; Slosar, Anže; Strauss, Michael A; Swanson, Molly E C; Thomas, Daniel; Tinker, Jeremy L; Tojeiro, Rita; Magaña, Mariana Vargas; Vazquez, Jose Alberto; Verde, Licia; Wake, David A; Wang, Yuting; Weinberg, David H; White, Martin; Wood-Vasey, W Michael; Yèche, Christophe; Zehavi, Idit; Zhai, Zhongxu; Zhao, Gong-Bo

    2016-01-01

    We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises 1.2 million massive galaxies over an effective area of 9329 deg^2 and volume of 18.7 Gpc^3, divided into three partially overlapping redshift slices centred at effective redshifts 0.38, 0.51, and 0.61. We measure the angular diameter distance DM and Hubble parameter H from the baryon acoustic oscillation (BAO) method after applying reconstruction to reduce non-linear effects on the BAO feature. Using the anisotropic clustering of the pre-reconstruction density field, we measure the product DM*H from the Alcock-Paczynski (AP) effect and the growth of structure, quantified by f{\\sigma}8(z), from redshift-space distortions (RSD). We combine measurements presented in seven companion papers into a set of consensus values and likelihoods, obtaining constraints that are tighter and more robust than those from any one m...

  15. CLASH-X: A Comparison of Lensing and X-ray Techniques for Measuring the Mass Profiles of Galaxy Clusters

    CERN Document Server

    Donahue, Megan; Mahdavi, Andisheh; Umetsu, Keiichi; Ettori, Stefano; Merten, Julian; Postman, Marc; Hoffer, Aaron; Baldi, Alessandro; Coe, Dan; Czakon, Nicole; Bartelmann, Mattias; Benitez, Narciso; Bouwens, Rychard; Bradley, Larry; Broadhurst, Tom; Ford, Holland; Gastaldello, Fabio; Grillo, Claudio; Infante, Leopoldo; Jouvel, Stephanie; Koekemoer, Anton; Kelson, Daniel; Lahav, Ofer; Lemze, Doron; Medezinski, Elinor; Melchior, Peter; Meneghetti, Massimo; Molino, Alberto; Moustakas, John; Moustakas, Leonidas A; Nonino, Mario; Rosati, Piero; Sayers, Jack; Seitz, Stella; Van der Wel, Arjen; Zheng, Wei; Zitrin, Adi

    2014-01-01

    We present profiles of temperature, gas mass, and hydrostatic mass estimated from X-ray observations of CLASH clusters. We compare measurements from XMM and Chandra and compare both sets to CLASH gravitational lensing mass profiles. We find that Chandra and XMM measurements of electron density and enclosed gas mass as functions of radius are nearly identical, indicating that any differences in hydrostatic masses inferred from X-ray observations arise from differences in gas-temperature estimates. Encouragingly, gas temperatures measured in clusters by XMM and Chandra are consistent with one another at ~100 kpc radii but XMM temperatures systematically decline relative to Chandra temperatures as the radius of the temperature measurement increases. One plausible reason for this trend is large-angle scattering of soft X-ray photons in excess of that amount expected from the standard XMM PSF correction. We present the CLASH-X mass-profile comparisons in the form of cosmology-independent and redshift-independent c...

  16. SACS: Spitzer Archival Cluster Survey

    Science.gov (United States)

    Stern, Daniel

    on cosmological results from ongoing Sunyaev-Zel'dovich (SZ) and X-ray cluster surveys. The identified clusters will be valuable for both astrophysics and cosmology. In terms of astrophysics, the redshift probed by the MIR color selection targets a key epoch in cluster development, when star formation is shutting down and the galaxies are becoming passive. Massive clusters also distort space-time around them, creating powerful gravitational telescopes that lens the distant universe. This both allows detailed studies of the lensed objects with otherwise unachievable sensitivity, as well as provides a unique probe of the mass distribution in the lensing cluster. In terms of cosmology, clusters are the most massive structures in the universe, and their space density is sensitive to basic cosmological parameters. Clusters identified by this program will become a lasting legacy of Spitzer, providing exciting targets for Chandra, Hubble, James Webb Space Telescope (JWST), Astro-H, Athena, as well as future 30-m class ground-based telescopes (e.g., GMT, ELT, TMT). The upcoming large-scale, space-based surveys of eROSITA, Euclid, and WFIRST all have distant cluster studies as key scientific goals. Our proposed survey will provide new high redshift targets for those satellites, enabling unique, exciting multi-wavelength studies of the Spitzer-selected sample, as well as a training set to identify additional high-redshift clusters outside of the Spitzer footprint.

  17. Weak lensing study of 16 DAFT/FADA clusters: Substructures and filaments

    Science.gov (United States)

    Martinet, Nicolas; Clowe, Douglas; Durret, Florence; Adami, Christophe; Acebrón, Ana; Hernandez-García, Lorena; Márquez, Isabel; Guennou, Loic; Sarron, Florian; Ulmer, Mel

    2016-05-01

    While our current cosmological model places galaxy clusters at the nodes of a filament network (the cosmic web), we still struggle to detect these filaments at high redshifts. We perform a weak lensing study for a sample of 16 massive, medium-high redshift (0.4 Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. The study is also based on archive data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. This research made use of data obtained from the Chandra Data Archive provided by the Chandra X-ray Center (CXC) and data obtained from the XMM-Newton Data Archive provided by the XMM-Newton Science Archive (XSA).

  18. LoCuSS: Calibrating Mass-Observables Scaling Relations for Cluster Cosmology with Subaru Weak Lensing Observations

    CERN Document Server

    Okabe, Nobuhiro; Finoguenov, Alexis; Takada, Masahiro; Smith, Graham P; Umetsu, Keiichi; Futamase, Toshifumi

    2010-01-01

    (Abridged) We present a joint weak-lensing/X-ray study of galaxy cluster mass-observable scaling relations, motivated by the critical importance of accurate calibration of mass proxies for future X-ray missions, including eROSITA. We use a sample of 12 clusters at z\\simeq0.2 that we have observed with Subaru and XMM-Newton to construct relationships between the weak-lensing mass (M), and three X-ray observables: gas temperature (T), gas mass (Mgas), and quasi-integrated gas pressure (Yx) at overdensities of \\Delta=2500, 1000, and 500 with respect to the critical density. We find that Mgas at \\Delta\\le1000 appears to be the most promising mass proxy of the three, because it has the lowest intrinsic scatter in mass at fixed observable: \\sigma _lnM\\simeq0.1, independent of cluster dynamical state. The scatter in mass at fixed T and Yx is a factor of \\sim2-3 larger than at fixed Mgas, which are indicative of the structural segregation that we find in the M-T and M-Yx relationships. Undisturbed clusters are found ...

  19. EIS Data on the Chandra Deep Field South Released

    Science.gov (United States)

    2001-03-01

    The purpose of this note is to announce that the ESO Imaging Survey programme has released a full set of optical/infrared data covering the socalled Chandra Deep Field South (CDF-S) rapidly becoming a favoured target for cosmological studies in the southern hemisphere. The field was originally selected for deep X-ray observations with Chandra and XMM. The former have already been completed producing the deepest high-resolution X-ray image ever taken with a total integration time of one million seconds. The data obtained by EIS include J and Ks infrared observations of an area of 0.1 square degree nearly matching the Chandra image down to JAB ~ 23.4 and KAB ~ 22.6 and UU'BVRI optical observations over 0.25 square degree, matching the XMM field of view, reaching 5 s limiting magnitudes of U'AB = 26.0, UAB = 25.7, BAB = 26.4, VAB = 25.4, RA B = 25.5 and IA B = 24.7 mag, as measured within a 2 ´ FWHM aperture.

  20. Continuum Theory (CT):. Its Particle-Tied Aether Yields a Continuous Auto-creation, Non-expanding Cosmology and New Light on Galaxy Evolution and Clusters

    Science.gov (United States)

    Osmaston, Miles F.

    2013-09-01

    shrinkage, with mass annihilation and emission of a GRB. Of special interest, relative to the arm's-length nature of BigBang cosmology, is that continuous auto-creation (CAC) cosmology is in principle available near-by for direct study and the development of strong observational constraints. In the context of (1), the very low metallicity (Pop II) of globular (star) clusters abundantly present in the haloes of galaxies points to them being (infallen?) local concentrations of quite young auto-creation. In that case the `blue straggler' stars more recently formed in their core regions may be our youngest examples of ongoing auto-creation. In summary, CT offers a much more directly observable Universe, with no Big Bang, CDM, or Dark Energy, and a CMB that records the true temperature of intergalactic space along the path taken by the radiation. Its closely cavity-radiation character arises from the random aether's transmission-related opacity (Olbers' Paradox) of the infinite CT Universe. Fundamentally, the aether's random motion constitutes all-penetrating random electromagnetic excitation at the atomic scale that may offer the accommodation between classical physics and stochastic quantum electrodynamics so long obstructed by Relativity Theory.

  1. The Chandra Galactic Bulge Survey

    NARCIS (Netherlands)

    Hynes, Robert I.; Jonker, P.G.; Bassa, C. G.; Dieball, A.; Greiss, S.; Maccarone, T. J.; Nelemans, G.; Steeghs, D.; Torres, M. A. P.; Britt, C. T.; Clem, J. L.; Gossen, L.; Grindlay, J. E.; Groot, P.J.; Kuiper, L.; Kuulkers, E.; Mendez, M.; Mikles, V. J.; Ratti, E. M.; Rea, N.; van Haaften, L.; Wijnands, R.; in't Zand, J. J. M.

    2011-01-01

    The Chandra Galactic Bulge Survey (CGBS) is a shallow but wide survey of two approximately 6x1 degree strips of the Galactic Bulge about a degree above and below the plane. The survey by design targets regions where extinction and crowding are manageable and optical counterparts are accessible to de

  2. The Chandra Galactic Bulge Survey

    NARCIS (Netherlands)

    Hynes, Robert I.; Jonker, P. G.; Bassa, C. G.; Nelemans, G.; Steeghs, D.; Torres, M. A. P.; Maccarone, T. J.; Greiss, S.; Clem, J.; Dieball, A.; Mikles, V. J.; Britt, C. T.; Gossen, L.; Collazzi, A. C.; Wijnands, R.; In't Zand, J. J. M.; Mendez, M.; Rea, N.; Kuulkers, E.; Ratti, E. M.; van Haaften, L. M.; Heinke, C.; Ozel, F.; Groot, P. J.; Verbunt, F.

    2012-01-01

    The Chandra Galactic Bulge Survey (GBS) is a shallow but wide survey of two approximately 6x1 degree strips of the Galactic Bulge about a degree above and below the plane. The survey by design targets regions where extinction and crowding are manageable and optical counterparts are accessible to det

  3. The Chandra Deep Field-North Survey and the Cosmic X-ray Background

    CERN Document Server

    Brandt, W N; Bauer, F E; Hornschemeier, A E

    2002-01-01

    Chandra has performed a 1.4 Ms survey centred on the Hubble Deep Field-North (HDF-N), probing the X-ray Universe 55-550 times deeper than was possible with pre-Chandra missions. We describe the detected point and extended X-ray sources and discuss their overall multiwavelength (optical, infrared, submillimeter, and radio) properties. Special attention is paid to the HDF-N X-ray sources, luminous infrared starburst galaxies, optically faint X-ray sources, and high-to-extreme redshift AGN. We also describe how stacking analyses have been used to probe the average X-ray emission properties of normal and starburst galaxies at cosmologically interesting distances. Finally, we discuss plans to extend the survey and argue that a 5-10 Ms Chandra survey would lay key groundwork for future missions such as XEUS and Generation-X.

  4. Cosmological constraints on ghost dark energy in the Brans-Dicke theory by using MCMC approach

    Science.gov (United States)

    Alavirad, Hamzeh; Sheykhi, Ahmad

    2014-06-01

    By using a Markov Chain Monte Carlo simulation, we investigate cosmological constraints on the ghost dark energy (GDE) model in the framework of the Brans-Dicke (BD) theory. A combination of the latest observational data of the cosmic microwave background radiation data from seven-year WMAP, the baryon acoustic oscillation data form the SDSS, the supernovae type Ia data from the Union2 and the X-ray gas mass fraction data from the Chandra X-ray observations of the largest relaxed galaxy clusters are used to perform constraints on GDE in the BD cosmology. In this paper, we consider both flat and non-flat universes together with interaction between dark matter and dark energy. The main cosmological parameters are obtained as: Ωbh2=0.0223-0.0013+0.0016, Ωch2=0.1149-0.0104+0.0088 and Ωk=0.0005-0.0073+0.0025. In addition, the Brans-Dicke parameter ω is estimated as 1/ω≃0.002.

  5. Cosmological Constraints on Ghost Dark Energy in the Brans-Dicke Theory by Using MCMC Approach

    CERN Document Server

    Alavirad, Hamzeh

    2014-01-01

    By using a Markov Chain Monte Carlo simulation, we investigate cosmological constraints on the ghost dark energy (GDE) model in the framework of the Brans-Dicke (BD) theory. A combination of the latest observational data of the cosmic microwave background radiation data from seven-year WMAP, the baryon acoustic oscillation data form the SDSS, the supernovae type Ia data from the Union2 and the X-ray gas mass fraction data from the Chandra X-ray observations of the largest relaxed galaxy clusters are used to perform constraints on GDE in the BD cosmology. In this paper, we consider both flat and non-flat universes together with interaction between dark matter and dark energy. The main cosmological parameters are obtained as: $\\Omega_{\\rm b}h^2= 0.0223^{+0.0016}_{-0.0013}$, $\\Omega_{\\rm c}h^2=0.1149^{+0.0088}_{-0.0104}$ and $\\Omega_{\\rm k}=0.0005^{+0.0025}_{-0.0073}$. In addition, the Brans-Dicke parameter $\\omega$ is estimated as $1/\\omega\\simeq 0.002$.

  6. Chandra Data Reveal Rapidly Whirling Black Holes

    Science.gov (United States)

    2008-01-01

    black holes," said co-investigator Richard Bower of Durham University. "This might help us explain the source of these incredible jets that we see stretching for enormous distances across space." One significant connection consequence of powerful, black-hole jets in galaxies in the centers of galaxy clusters is that they can pump enormous amounts of energy into their environments, and heat the gas around them. This heating prevents the gas from cooling, and affects the rate at which new stars form, thereby limiting the size of the central galaxy. Understanding the details of this fundamental feedback loop between supermassive black holes and the formation of the most massive galaxies remains an important goal in astrophysics. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

  7. Observational cosmology

    NARCIS (Netherlands)

    Sanders, RH; Papantonopoulos, E

    2005-01-01

    I discuss the classical cosmological tests, i.e., angular size-redshift, flux-redshift, and galaxy number counts, in the light of the cosmology prescribed by the interpretation of the CMB anisotropies. The discussion is somewhat of a primer for physicists, with emphasis upon the possible systematic

  8. Large Scale Clustering of Sloan Digital Sky Survey Quasars: Impact of the Baryon Density and the Cosmological Constant

    CERN Document Server

    Yahata, K; Kayo, I; Matsubara, T; Connolly, A; Vanden Berk, Daniel E; Sheth, R; Szapudi, I; Anderson, S F; Bahcall, Neta A; Brinkmann, J; Csabai, I; Fan, X; Loveday, J; York, A S; Yahata, Kazuhiro; Suto, Yasushi; Kayo, Issha; Matsubara, Takahiko; Connolly, Andrew; Berk, Daniel Vanden; Sheth, Ravi; Szapudi, Istvan; Anderson, Scott F.; Bahcall, Neta; Brinkmann, Jon; Csabai, Istvan; Fan, Xiaohui; Loveday, Jon; York, Alexander S. Szalay and Donald

    2004-01-01

    We report the first result of the clustering analysis of Sloan Digital Sky Survey (SDSS) quasars. We compute the two-point correlation function (2PCF) of SDSS quasars in redshift space at $10h^{-1}{\\rm Mpc} < s < 1h^{-1}{\\rm Gpc}$, with particular attention to its baryonic signature. Our sample consists of 20303 quasars extracted from the SDSS Data Release 3 (DR3). The redshift range of the sample is $0.16 \\le z \\le 2.24$ and the reddening-corrected $i$-band apparent magnitude range is $15.0 \\le m_{i,{\\rm rc}} \\le 19.1$. Due to the relatively low number density of the quasar sample, the bump in the power spectrum due to the baryon density, $\\Omega_{\\rm b}$, is not clearly visible. The effect of the baryon density is, however, to shift the zero-crossing scale $s_{\\rm zero}$ of the 2PCF. The sensitivity of the zero crossing to the baryon density makes it an interesting alternate measure of the baryonic signature. Assuming a scale-independent linear bias and the spatially flat universe, i.e., $\\Omega_{\\rm ...

  9. Chandra Observation of Abell 2065: An Unequal Mass Merger?

    CERN Document Server

    Chatzikos, M; Sarazin, C L; Chatzikos, Marios; Sarazin, Craig L.

    2006-01-01

    We present an analysis of a 41 ks Chandra observation of the merging cluster Abell 2065 with the ACIS-I detector. Previous observations with ROSAT and ASCA provided evidence for an ongoing merger, but also suggested that there were two surviving cooling cores, which were associated with the two cD galaxies in the center of the cluster. The Chandra observation reveals only one X-ray surface brightness peak, which is associated with the more luminous, southern cD galaxy. The gas related with that peak is cool and displaced slightly from the position of the cD. The data suggest that this cool material has formed a cold front. On the other hand, in the higher spatial resolution Chandra image, the second feature to the north is not associated with the northern cD; rather, it appears to be a trail of gas behind the main cD. We argue that only one of the two cooling cores has survived the merger, although it is possible that the northern cD may not have possessed a cool core prior to the merger. We use the cool core...

  10. The Blanco Cosmology Survey: Data Reduction, Calibration and Photometric Redshift Estimation to Four Distant Galaxy Clusters Discovered by the South Pole Telescope

    Science.gov (United States)

    Ngeow, Chow Choong; Mohr, J.; Zenteno, A.; Data Management, DES; BCS; SPT Collaborations

    2009-01-01

    The Blanco Cosmology Survey (BCS) is designed to enable a study of the cosmic acceleration using multiple techniques. To date, BCS has acquired Sloan griz band imaging data from 60 nights (15 nights per year from 2005 to 2008) using the Blanco 4m Telescope located at CTIO. The astronomical imaging data taken from this survey have been processed on high performance computer TeraGrid platforms at NCSA, using the automated Dark Energy Survey (DES) data management (DM) system. The DES DM system includes (1) middlewares for controlling and managing the processing jobs, and serve as an application container encapsulating the scientific codes; and (2) DES archive, which includes filesystem nodes, a relational database and a data access framework, to support the pipeline processing, data storage and scientific analyzes. Photometric solution module (PSM) were run on photometric nights to determine the zeropoints (ZP) and other photometric solutions. We remapped and coadded the images that lie within the pre-defined coadd tiles in the sky. When running the coaddition pipeline, we determined the ZP for each images using the photometric ZP from PSM, the magnitude offsets between overlapping images, and the sky brightness ratio for CCDs within a given exposure. We also applied aperture correction and color-term correction to the coadded catalogs. Satisfactory photometric and astrometric precision were achieved. These enabled initial estimation of photometric redshifts using ANNz codes, trained from 5000 galaxies with spectroscopic redshifts. RMS in the photometric redshifts ranges from 0.05 to 0.1 in sigma_z/(1+z) for redshift extended to z=1. We used the BCS data to optically confirm and estimate redshifts for four of the highest S/N galaxy clusters discovered with the South Pole Telescope using the Sunyaev-Zel'dovich Effect.

  11. Clustering, Cosmology and a New Era of Black Hole Demographics - II. The Conditional Luminosity Functions of Type 2 and Type 1 Active Galactic Nuclei

    Science.gov (United States)

    Ballantyne, D. R.

    2016-09-01

    The orientation-based unification model of active galactic nuclei (AGNs) posits that the principle difference between obscured (Type 2) and unobscured (Type 1) AGNs is the line-of-sight into the central engine. If this model is correct than there should be no difference in many of the properties of AGN host galaxies (e.g., the mass of the surrounding dark matter haloes). However, recent clustering analyses of Type 1 and Type 2 AGNs have provided some evidence for a difference in the halo mass, in conflict with the orientation-based unified model. In this work, a method to compute the Conditional Luminosity Function (CLF) of Type 2 and Type 1 AGNs is presented. The CLF allows many fundamental halo properties to be computed as a function of AGN luminosity, which we apply to the question of the host halo masses of Type 1 and 2 AGNs. By making use of the total AGN CLF, the Type 1 X-ray luminosity function, and the luminosity-dependent Type 2 AGN fraction, the CLFs of Type 1 and 2 AGNs are calculated at z ≈ 0 and 0.9. At both z, there is no statistically significant difference in the mean halo mass of Type 2 and 1 AGNs at any luminosity. There is marginal evidence that Type 1 AGNs may have larger halo masses than Type 2s, which would be consistent with an evolutionary picture where quasars are initially obscured and then subsequently reveal themselves as Type 1s. As the Type 1 lifetime is longer, the host halo will increase somewhat in mass during the Type 1 phase. The CLF technique will be a powerful way to study the properties of many AGNs subsets (e.g., radio-loud, Compton-thick) as future wide-area X-ray and optical surveys substantially increase our ability to place AGNs in their cosmological context.

  12. Highlights and discoveries from the Chandra X-ray Observatory.

    Science.gov (United States)

    Tananbaum, H; Weisskopf, M C; Tucker, W; Wilkes, B; Edmonds, P

    2014-06-01

    Within 40 years of the detection of the first extra-solar x-ray source in 1962, NASA's Chandra X-ray Observatory has achieved an increase in sensitivity of 10 orders of magnitude, comparable to the gain in going from naked-eye observations to the most powerful optical telescopes over the past 400 years. Chandra is unique in its capabilities for producing sub-arcsecond x-ray images with 100-200 eV energy resolution for energies in the range 0.08 black holes; the growth of supermassive black holes and their role in the regulation of star formation and growth of galaxies; impacts of collisions, mergers, and feedback on growth and evolution of groups and clusters of galaxies; and properties of dark matter and dark energy. PMID:24913425

  13. Magnetic Bubbles in Galaxy Clusters

    OpenAIRE

    McNamara, B. R.

    2003-01-01

    I discuss Chandra X-ray Observatory measurements of cavities in galaxy clusters and their implications for heating the intracluster gas. The emerging paradigm for cooling flows has important implications for understanding self-regulated galaxy formation.

  14. Gravitational Lens Helps Chandra Find Rare Type of Black Hole

    Science.gov (United States)

    2000-03-01

    A team of astronomers from England and France have reported strong evidence for the existence of a rare type of black hole, called a Type 2 quasar. Using NASA's Chandra X-ray Observatory, they have discovered a powerful source of X rays that appears to be a giant black hole that is hidden from optical telescopes by a veil of obscuring material. The latest discovery comes from a team led by British astronomers Andrew Fabian of the Institute of Astronomy in Cambridge and Ian Smail of the University of Durham. They used Chandra, NASA's Hubble Space Telescope, and the James Clerk Maxwell submillimeter telescope on Mauna Kea in Hawaii. By concentrating their search near two galaxy clusters, the astronomers exploited a gravitational lensing effect that can lead to a significant brightening of distant sources. Four new X-ray sources and seven submillimeter sources were discovered. The brightest X-ray source is concentrated in the center of a distant galaxy. The point-like source has a deficit of low energy X rays, consistent with absorption by a thick cloud of gas. The combination of powerful X-ray emission, absorption of low energy X rays, and the relatively normal optical appearance of the galaxy led the scientists to conclude that the source is a strong contender to be a genuine Type 2 quasar. Type 2 quasars have been predicted to exist by a popular model for quasars. Their discovery would confirm the so-called unified model for quasars, and help clarify the nature of the pervasive background glow at X-ray and submillimeter energies. Evidence for Type 2 quasars has been reported by other researchers, but the data were ambiguous. Now, the cloud of uncertainty is lifting, as scientists use Chandra to intensify the search. According to the unified model of quasars, a thick doughnut of gas and dust surrounds a central black hole. The source looks different, depending on whether it is observed through the doughnut, through the hole, or at an intermediate angle. In extreme

  15. Cosmological singularity

    CERN Document Server

    Belinski, V

    2009-01-01

    The talk at international conference in honor of Ya. B. Zeldovich 95th Anniversary, Minsk, Belarus, April 2009. The talk represents a review of the old results and contemporary development on the problem of cosmological singularity.

  16. Clustering

    Directory of Open Access Journals (Sweden)

    Jinfei Liu

    2013-04-01

    Full Text Available DBSCAN is a well-known density-based clustering algorithm which offers advantages for finding clusters of arbitrary shapes compared to partitioning and hierarchical clustering methods. However, there are few papers studying the DBSCAN algorithm under the privacy preserving distributed data mining model, in which the data is distributed between two or more parties, and the parties cooperate to obtain the clustering results without revealing the data at the individual parties. In this paper, we address the problem of two-party privacy preserving DBSCAN clustering. We first propose two protocols for privacy preserving DBSCAN clustering over horizontally and vertically partitioned data respectively and then extend them to arbitrarily partitioned data. We also provide performance analysis and privacy proof of our solution..

  17. Cosmological Perturbations

    Science.gov (United States)

    Lesgourges, J.

    2013-08-01

    We present a self-contained summary of the theory of linear cosmological perturbations. We emphasize the effect of the six parameters of the minimal cosmological model, first, on the spectrum of Cosmic Microwave Background temperature anisotropies, and second, on the linear matter power spectrum. We briefly review at the end the possible impact of a few non-minimal dark matter and dark energy models.

  18. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Signs of neutrino mass in current cosmological datasets

    OpenAIRE

    Beutler, Florian; Saito, Shun; Brownstein, Joel R.; Chuang, Chia-Hsun; Cuesta, Antonio J.; Percival, Will J.; Ross, Ashley J.; Ross, Nicholas P.; Schneider, Donald P.; Samushia, Lado; Sanchez, Ariel G.; Seo, Hee-Jong; Tinker, Jeremy L.; Wagner, Christian; Weaver, Benjamin A.

    2014-01-01

    We investigate the cosmological implications of the latest growth of structure measurement from the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS Data Release 11 with particular focus on the sum of the neutrino masses, $\\sum m_{\

  19. Chandra Reviews Black Hole Musical: Epic But Off-Key

    Science.gov (United States)

    2006-10-01

    A gigantic sonic boom generated by a supermassive black hole has been found with NASA's Chandra X-ray Observatory, along with evidence for a cacophony of deep sound. This discovery was made by using data from the longest X-ray observation ever of M87, a nearby giant elliptical galaxy. M87 is centrally located in the Virgo cluster of galaxies and is known to harbor one of the Universe's most massive black holes. Scientists detected loops and rings in the hot, X-ray emitting gas that permeates the cluster and surrounds the galaxy. These loops provide evidence for periodic eruptions that occurred near the supermassive black hole, and that generate changes in pressure, or pressure waves, in the cluster gas that manifested themselves as sound. Chandra Low Energy X-ray Images of M87 Chandra Low Energy X-ray Images of M87 "We can tell that many deep and different sounds have been rumbling through this cluster for most of the lifetime of the Universe," said William Forman of the Harvard-Smithsonian Center for Astrophysics (CfA). The outbursts in M87, which happen every few million years, prevent the huge reservoir of gas in the cluster from cooling and forming many new stars. Without these outbursts and resultant heating, M87 would not be the elliptical galaxy it is today. "If this black hole wasn't making all of this noise, M87 could have been a completely different type of galaxy," said team member Paul Nulsen, also of the CfA, "possibly a huge spiral galaxy about 30 times brighter than the Milky Way." Chandra High Energy X-ray Image of M87 Chandra High Energy X-ray Image of M87 The outbursts result when material falls toward the black hole. While most of the matter is swallowed, some of it was violently ejected in jets. These jets are launched from regions close to the black hole (neither light nor sound can escape from the black hole itself) and push into the cluster's gas, generating cavities and sound which then propagate outwards. Chandra's M87 observations also

  20. CosmicPy: Interactive cosmology computations

    Science.gov (United States)

    Lanusse, Francois; Rassat, Anais; Starck, Jean-Luc

    2016-01-01

    CosmicPy performs simple and interactive cosmology computations for forecasting cosmological parameters constraints; it computes tomographic and 3D Spherical Fourier-Bessel power spectra as well as Fisher matrices for galaxy clustering. Written in Python, it relies on a fast C++ implementation of Fourier-Bessel related computations, and requires NumPy, SciPy, and Matplotlib.

  1. Chandra Observations of Neutron Stars -- An Overview

    OpenAIRE

    Weisskopf, M. C.

    2002-01-01

    We present a brief review of Chandra observations of neutron stars, with a concentration on neutron stars in supernova remnants. The early Chandra results clearly demonstrate how critical the angular resolution has been in order to separate the neutron star emission from the surrounding nebulosity.

  2. Chandra Multi-wavelength Plane Survey

    NARCIS (Netherlands)

    P. Zhao; J.E. Grindlay; J. Hong; M. Servillat; M. van den Berg

    2014-01-01

    Chandra Multi-wavelength Plane Survey (ChaMPlane) surveys the X-ray point sources discovered by the Chandra X-ray Observatory in the galactic plane in order to constrain the populations of faint (L x ≤ 1033 erg/s) accretion-powered sources in the Galaxy. This multi-wavelength survey includes data fr

  3. Cosmological simulations using GCMHD+

    Science.gov (United States)

    Barnes, David J.; Kawata, Daisuke; Wu, Kinwah

    2012-03-01

    Radio observations of galaxy clusters show that the intracluster medium is permeated by ? magnetic fields. The origin and evolution of these cosmological magnetic fields is currently not well understood, and so their impact on the dynamics of structure formation is not known. Numerical simulations are required to gain a greater understanding and produce predictions for the next generation of radio telescopes. We present the galactic chemodynamics smoothed particle magnetohydrodynamics (SPMHD) code (GCMHD+), which is an MHD implementation for the cosmological smoothed particle hydrodynamics code GCD+. The results of 1D, 2D and 3D tests are presented and the performance of the code is shown relative to the ATHENA grid code. GCMHD+ shows good agreement with the reference solutions produced by ATHENA. The code is then used to simulate the formation of a galaxy cluster with a simple primordial magnetic field embedded in the gas. A homogeneous seed field of 3.5 × 10-11 G is amplified by a factor of 103 during the formation of the cluster. The results show good agreement with the profiles found in other magnetic cluster simulations of similar resolution.

  4. Cosmological principle

    Energy Technology Data Exchange (ETDEWEB)

    Wesson, P.S.

    1979-10-01

    The Cosmological Principle states: the universe looks the same to all observers regardless of where they are located. To most astronomers today the Cosmological Principle means the universe looks the same to all observers because density of the galaxies is the same in all places. A new Cosmological Principle is proposed. It is called the Dimensional Cosmological Principle. It uses the properties of matter in the universe: density (rho), pressure (p), and mass (m) within some region of space of length (l). The laws of physics require incorporation of constants for gravity (G) and the speed of light (C). After combining the six parameters into dimensionless numbers, the best choices are: 8..pi..Gl/sup 2/ rho/c/sup 2/, 8..pi..Gl/sup 2/ rho/c/sup 4/, and 2 Gm/c/sup 2/l (the Schwarzchild factor). The Dimensional Cosmological Principal came about because old ideas conflicted with the rapidly-growing body of observational evidence indicating that galaxies in the universe have a clumpy rather than uniform distribution. (SC)

  5. MPS/CAS Partner Group on Cosmology

    Institute of Scientific and Technical Information of China (English)

    Jing Yipeng; Gerhard B(o)rner

    2004-01-01

    @@ The Partner Group does research in cosmology, focussing on the quantitative modeling of the structure and evolution of galaxies and galaxy clusters, the pattern of galaxies and of larger structures.

  6. Primordial cosmology

    Science.gov (United States)

    Montani, Giovanni

    1. Historical picture. 1.1. The concept of universe through the centuries. 1.2. The XIX century knowledge. 1.3. Birth of scientific cosmology. 1.4. The genesis of the hot big bang model. 1.5. Guidelines to the literature -- 2. Fundamental tools. 2.1. Einstein equations. 2.2. Matter fields. 2.3. Hamiltonian formulation of the dynamics. 2.4. Synchronous reference system. 2.5. Tetradic formalism. 2.6. Gauge-like formulation of GR. 2.7. Singularity theorems. 2.8. Guidelines to the literature -- 3. The structure and dynamics of the isotropic universe. 3.1. The RW geometry. 3.2. The FRW cosmology. 3.3. Dissipative cosmologies. 3.4. Inhomogeneous fluctuations in the universe. 3.5. General relativistic perturbation theory. 3.6. The Lemaitre-Tolmann-Bondi spherical solution. 3.7. Guidelines to the literature -- 4. Features of the observed universe. 4.1. Current status: The concordance model. 4.2. The large-scale structure. 4.3. The acceleration of the universe. 4.4. The cosmic microwave background. 4.5. Guidelines to the literature -- 5. The theory of inflation. 5.1. The shortcomings of the standard cosmology. 5.2. The inflationary paradigm. 5.3. Presence of a self-interacting scalar field. 5.4. Inflationary dynamics. 5.5. Solution to the shortcomings of the standard cosmology. 5.6. General features. 5.7. Possible explanations for the present acceleration of the universe. 5.8. Guidelines to the literature -- 6. Inhomogeneous quasi-isotropic cosmologies. 6.1. Quasi-isotropic solution. 6.2. The presence of ultrarelativistic matter. 6.3. The role of a massless scalar field. 6.4. The role of an electromagnetic field. 6.5. Quasi-isotropic inflation. 6.6. Quasi-isotropic viscous solution. 6.7. Guidelines to the literature -- 7. Homogeneous universes. 7.1. Homogeneous cosmological models. 7.2. Kasner solution. 7.3. The dynamics of the Bianchi models. 7.4. Bianchi types VIII and IX models. 7.5. Dynamical systems approach. 7.6. Multidimensional homogeneous universes. 7.7. Guidelines

  7. Chandra Observations of Starburst Galaxies

    Science.gov (United States)

    Prestwich, Andrea; Lavoie, Anthony R. (Technical Monitor)

    2000-01-01

    We present early X-ray results from Chandra for two starburst galaxies, M82 and NGC3256, obtained using AXAF CCD Imaging Spectrometer (ACIS-I) and the HRC. For M82 the arcsecond spatial resolution enables us to separate the point source component from the extended emission for the first time. Astrometry reveals that most of the X-ray sources are not coincident with the family of compact radio sources believed to be Super Nova Remnants (SNRs). In addition, based on three epoch Chandra observations, several of the X-ray sources are clearly variable indicating that they are binaries. When we deconvolve the extended and point source components detected in the hard X-ray band, we find that 50 percent arises from the extended component. This fact, together with its morphology, constrains the various models proposed to explain the hard X-ray emission. For NGC3256 we resolve two closely separated nuclei. These new data support a pure starburst origin for the total X-ray emission rather than a composite AGN/starburst, thereby making NGC3256 one of the most X-ray luminous starburst galaxies known.

  8. Chandra "Hears" A Black Hole For The First Time

    Science.gov (United States)

    2003-09-01

    NASA's Chandra X-ray Observatory detected sound waves, for the first time, from a super-massive black hole. The "note" is the deepest ever detected from an object in the universe. The tremendous amounts of energy carried by these sound waves may solve a longstanding problem in astrophysics. The black hole resides in the Perseus cluster, located 250 million light years from Earth. In 2002, astronomers obtained a deep Chandra observation that shows ripples in the gas filling the cluster. These ripples are evidence for sound waves that have traveled hundreds of thousands of light years away from the cluster's central black hole. perseus animation Illustration of Ripples in Perseus "We have observed the prodigious amounts of light and heat created by black holes, now we have detected the sound," said Andrew Fabian of the Institute of Astronomy (IoA) in Cambridge, England, and leader of the study. In musical terms, the pitch of the sound generated by the black hole translates into the note of B flat. But, a human would have no chance of hearing this cosmic performance, because the note is 57 octaves lower than middle-C (by comparison a typical piano contains only about seven octaves). At a frequency over a million, billion times deeper than the limits of human hearing, this is the deepest note ever detected from an object in the universe. "The Perseus sound waves are much more than just an interesting form of black hole acoustics," said Steve Allen, also of the IoA and a co-investigator in the research. "These sound waves may be the key in figuring out how galaxy clusters, the largest structures in the universe, grow," Allen said. For years astronomers have tried to understand why there is so much hot gas in galaxy clusters and so little cool gas. Hot gas glowing with X-rays should cool, and the dense central gas should cool the fastest. The pressure in this cool central gas should then fall, causing gas further out to sink in towards the galaxy, forming trillions of

  9. LoCuSS: Testing hydrostatic equilibrium in galaxy clusters

    CERN Document Server

    Smith, G P; Okabe, N; Ziparo, F; Mulroy, S L; Babul, A; Finoguenov, A; McCarthy, I G; Lieu, M; Bahe, Y; Bourdin, H; Evrard, A E; Futamase, T; Haines, C P; Jauzac, M; Marrone, D P; Martino, R; May, P E; Taylor, J E; Umetsu, K

    2015-01-01

    We test the assumption of hydrostatic equilibrium in an X-ray luminosity selected sample of 50 galaxy clusters at $0.15Cluster Substructure Survey (LoCuSS). Our weak-lensing measurements of $M_{500}$ control systematic biases to sub-4 per cent, and our hydrostatic measurements of the same achieve excellent agreement between XMM-Newton and Chandra. The mean ratio of X-ray to lensing mass for these 50 clusters is $\\beta_{\\rm X}=0.95\\pm0.05$, and for the 44 clusters also detected by Planck, the mean ratio of Planck mass estimate to LoCuSS lensing mass is $\\beta_{\\rm P}=0.95\\pm0.04$. Based on a careful like-for-like analysis, we find that LoCuSS, the Canadian Cluster Comparison Project (CCCP), and Weighing the Giants (WtG) agree on $\\beta_{\\rm P}\\simeq0.9-0.95$ at $0.15cosmology results from the cosmic microwave background and galaxy cluster counts.

  10. Dimensionless cosmology

    CERN Document Server

    Narimani, Ali; Scott, Douglas

    2011-01-01

    Although it is possible that some fundamental physical constants could vary in time, it is important to only consider dimensionless combinations, such as the fine structure constant or the equivalent coupling constant for gravity. Once all such dimensionless numbers have been given, then we can be sure that our cosmological picture is governed by the same physical laws as that of another civilization with an entirely different set of units. An additional feature of the standard model of cosmology raises an extra complication, namely that the epoch at which we live is a crucial part of the model. This can be defined by giving the value of any one of the evolving cosmological parameters. It takes some care to avoid inconsistent results for constraints on variable constants, which could be caused by effectively fixing more than one parameter today. We show examples of this effect by considering in some detail the physics of Big Bang nucleosynthesis, recombination and microwave background anisotropies, being care...

  11. Dark Matter and Baryons in the Most X-ray Luminous and Merging Galaxy Cluster RX J1347.5-1145

    CERN Document Server

    Bradac, Marusa; Erben, Thomas; McCourt, Michael; Million, Evan; Mantz, Adam; Allen, Steve; Blandford, Roger; Halkola, Aleksi; Hildebrand, Hendrik; Lombardi, Marco; Marshall, Phil; Schneider, Peter; Treu, Tommaso; Kneib, Jean-Paul

    2007-01-01

    The galaxy cluster RX J1347-1145 is one of the most X-ray luminous and most massive clusters known. Its extreme mass makes it a prime target for studying issues addressing cluster formation and cosmology. In this paper we present new high-resolution HST/ACS and Chandra X-ray data. The high resolution and sensitivity of ACS enabled us to detect and quantify several new multiply imaged sources, we now use a total of eight for the strong lensing analysis. Combining this information with shape measurements of weak lensing sources in the central regions of the cluster, we derive a high-resolution, absolutely-calibrated mass map. This map provides the best available quantification of the total mass of the central part of the cluster to date. We compare the reconstructed mass with that inferred from the new Chandra X-ray data, and conclude that both mass estimates agree extremely well in the observed region, namely within 400 / h_70 kpc of the cluster center. In addition we study the major baryonic components (gas a...

  12. Chandra mapping of the cosmic web converging on the virialization region of Abell 1795

    Science.gov (United States)

    Vikhlinin, Alexey

    2014-09-01

    Detailed observations of the "cosmic melting pot" in the virialization zone of rich galaxy clusters are a fairly new territory for the physics of clusters and the intergalactic medium. The first step has been taken with a deep Chandra study of A133, which has provided a uniquely detailed picture of the Cosmic Web converging onto the cluster virial radius and demonstrated that Chandra can probe to fainter surface brightness levels than any other X-ray observatory now operating. Many of the results from the A133 observation are potentially game-changers for our understanding of the virialization region and its proper modeling. We now need to follow this up with a similarly deep observation of at least one more cluster.

  13. Cosmological inflation

    CERN Document Server

    Enqvist, K

    2012-01-01

    The very basics of cosmological inflation are discussed. We derive the equations of motion for the inflaton field, introduce the slow-roll parameters, and present the computation of the inflationary perturbations and their connection to the temperature fluctuations of the cosmic microwave background.

  14. Cosmological Simulations using GCMHD+

    CERN Document Server

    Barnes, David J; Wu, Kinwah

    2011-01-01

    Radio observations of galaxy clusters show that the intra cluster medium is permeated by \\mu G magnetic fields. The origin and evolution of these cosmological magnetic fields is currently not well understood and so their impact on the dynamics of structure formation is not known. Numerical simulations are required to gain a greater understanding and produce predictions for the next generation of radio telescopes. We present the galactic chemodynamics smoothed particle magnetohydrodynamic (SPMHD) code (GCMHD+), which is an MHD implementation for the cosmological smoothed particle hydrodynamic code GCD+. The results of 1, 2 and 3 dimensional tests are presented and the performance of the code is shown relative to the ATHENA grid code. GCMHD+ shows good agreement with the reference solutions produced by ATHENA. The code is then used to simulate the formation of a galaxy cluster with a simple primordial magnetic field embedded in the gas. A homogeneous seed field of 10^-11 G is amplified by a factor of 10^3 durin...

  15. Weak lensing study of 16 DAFT/FADA clusters: Substructures and filaments

    Science.gov (United States)

    Martinet, Nicolas; Clowe, Douglas; Durret, Florence; Adami, Christophe; Acebrón, Ana; Hernandez-García, Lorena; Márquez, Isabel; Guennou, Loic; Sarron, Florian; Ulmer, Mel

    2016-05-01

    While our current cosmological model places galaxy clusters at the nodes of a filament network (the cosmic web), we still struggle to detect these filaments at high redshifts. We perform a weak lensing study for a sample of 16 massive, medium-high redshift (0.4 securing their detection with noise resampling techniques. Taking advantage of the large field of view of our data, we study cluster environment, adding information from galaxy density maps at the cluster redshift and from X-ray images when available. We find that clusters show a large variety of weak lensing maps at large scales and that they may all be embedded in filamentary structures at megaparsec scale. We classify these clusters in three categories according to the smoothness of their weak lensing contours and to the amount of substructures: relaxed (~7%), past mergers (~21.5%), and recent or present mergers (~71.5%). The fraction of clusters undergoing merging events observationally supports the hierarchical scenario of cluster growth, and implies that massive clusters are strongly evolving at the studied redshifts. Finally, we report the detection of unusually elongated structures in CLJ0152, MACSJ0454, MACSJ0717, A851, BMW1226, MACSJ1621, and MS1621. This study is based on observations obtained with MegaCam, a joint project of CFHT and CEA/IRFU, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. The study is also based on archive data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. This research made use of data obtained from the Chandra Data Archive provided by the Chandra X-ray Center (CXC) and data obtained from the XMM-Newton Data Archive provided by the XMM-Newton Science Archive (XSA).

  16. Axion cosmology

    Science.gov (United States)

    Marsh, David J. E.

    2016-07-01

    Axions comprise a broad class of particles that can play a major role in explaining the unknown aspects of cosmology. They are also well-motivated within high energy physics, appearing in theories related to CP-violation in the standard model, supersymmetric theories, and theories with extra-dimensions, including string theory, and so axion cosmology offers us a unique view onto these theories. I review the motivation and models for axions in particle physics and string theory. I then present a comprehensive and pedagogical view on the cosmology and astrophysics of axion-like particles, starting from inflation and progressing via BBN, the CMB, reionization and structure formation, up to the present-day Universe. Topics covered include: axion dark matter (DM); direct and indirect detection of axions, reviewing existing and future experiments; axions as dark radiation; axions and the cosmological constant problem; decays of heavy axions; axions and stellar astrophysics; black hole superradiance; axions and astrophysical magnetic fields; axion inflation, and axion DM as an indirect probe of inflation. A major focus is on the population of ultralight axions created via vacuum realignment, and its role as a DM candidate with distinctive phenomenology. Cosmological observations place robust constraints on the axion mass and relic density in this scenario, and I review where such constraints come from. I next cover aspects of galaxy formation with axion DM, and ways this can be used to further search for evidence of axions. An absolute lower bound on DM particle mass is established. It is ma > 10-24eV from linear observables, extending to ma ≳ 10-22eV from non-linear observables, and has the potential to reach ma ≳ 10-18eV in the future. These bounds are weaker if the axion is not all of the DM, giving rise to limits on the relic density at low mass. This leads to the exciting possibility that the effects of axion DM on structure formation could one day be detected

  17. CLASH-X: A comparison of lensing and X-ray techniques for measuring the mass profiles of galaxy clusters

    Energy Technology Data Exchange (ETDEWEB)

    Donahue, Megan; Voit, G. Mark; Hoffer, Aaron; Baldi, Alessandro [Physics and Astronomy Department, Michigan State University, East Lansing, MI 48824 (United States); Mahdavi, Andisheh [San Francisco State University, San Francisco, CA 94132 (United States); Umetsu, Keiichi; Czakon, Nicole [Institute of Astronomy and Astrophysics, Academia Sinica, Roosevelt Road, Taipei 10617, Taiwan (China); Ettori, Stefano [INFN, Sezione di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Merten, Julian [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Postman, Marc; Coe, Dan; Bradley, Larry [STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bartelmann, Mattias [Universität Heidelberg, Zentrum für Astronomie, Philosophenweg 12, D-69120 Heidelberg (Germany); Benitez, Narciso [Instituto de Astrofisica de Andalucia (CSIC), C/Camino Bajo de Huétor 24, Granada E-18008 (Spain); Bouwens, Rychard [Leiden Observatories, Niels Bohrweb 2, NL-2333 CA Leiden (Netherlands); Broadhurst, Tom [Department of Theoretical Physics, University of the Basque Country, E-48080 Bilbao (Spain); Ford, Holland [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218 (United States); Gastaldello, Fabio [INAF-IASF, via Bassini 15, I-20133 Milan (Italy); Grillo, Claudio [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Infante, Leopoldo, E-mail: donahue@pa.msu.edu [Dept Astronomía-Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, 22 Santiago (Chile); and others

    2014-10-20

    We present profiles of temperature, gas mass, and hydrostatic mass estimated from new and archival X-ray observations of CLASH clusters. We compare measurements derived from XMM and Chandra observations with one another and compare both to gravitational lensing mass profiles derived with CLASH Hubble Space Telescope and Subaru Telescope lensing data. Radial profiles of Chandra and XMM measurements of electron density and enclosed gas mass are nearly identical, indicating that differences in hydrostatic masses inferred from X-ray observations arise from differences in gas-temperature measurements. Encouragingly, gas temperatures measured in clusters by XMM and Chandra are consistent with one another at ∼100-200 kpc radii, but XMM temperatures systematically decline relative to Chandra temperatures at larger radii. The angular dependence of the discrepancy suggests that additional investigation on systematics such as the XMM point-spread function correction, vignetting, and off-axis responses is yet required. We present the CLASH-X mass-profile comparisons in the form of cosmology-independent and redshift-independent circular-velocity profiles. We argue that comparisons of circular-velocity profiles are the most robust way to assess mass bias. Ratios of Chandra hydrostatic equilibrium (HSE) mass profiles to CLASH lensing profiles show no obvious radial dependence in the 0.3-0.8 Mpc range. However, the mean mass biases inferred from the weak-lensing (WL) and SaWLens data are different. As an example, the weighted-mean value at 0.5 Mpc is (b) = 0.12 for the WL comparison and (b) = –0.11 for the SaWLens comparison. The ratios of XMM HSE mass profiles to CLASH lensing profiles show a pronounced radial dependence in the 0.3-1.0 Mpc range, with a weighted mean mass bias value rising to (b) ≳ 0.3 at ∼1 Mpc for the WL comparison and (b) ≈ 0.25 for the SaWLens comparison. The enclosed gas mass profiles from both Chandra and XMM rise to a value ≈1/8 times the total

  18. Dionysian cosmology

    CERN Document Server

    Neves, J C S

    2015-01-01

    In the Nietzschean philosophy, the concept of force from physics is important to build one of its main concepts: the will to power. The concept of force, which Nietzsche found out in the Classical Mechanics, almost disappears in the physics of the XX century with the Quantum Field Theory and General Relativity. Is the Nietzschean world as contending forces, a Dionysian cosmology, possible in the current science?

  19. Cosmological wormholes

    CERN Document Server

    Kirillov, A A

    2015-01-01

    We describe in details the procedure how the Lobachevsky space can be factorized to a space of the constant negative curvature filled with a gas of wormholes. We show that such wormholes have throat sections in the form of tori and are traversable and stable in the cosmological context. The relation of such wormholes to the dark matter phenomenon is briefly described. We also discuss the possibility of the existence of analogous factorizations for all types of homogeneous spaces.

  20. Cosmological wormholes

    Science.gov (United States)

    Kirillov, A. A.; Savelova, E. P.

    2016-05-01

    We describe in details the procedure how the Lobachevsky space can be factorized to a space of the constant negative curvature filled with a gas of wormholes. We show that such wormholes have throat sections in the form of tori and are traversable and stable in the cosmological context. The relation of such wormholes to the dark matter phenomenon is briefly described. We also discuss the possibility of the existence of analogous factorizations for all types of homogeneous spaces.

  1. Medieval Cosmology

    Science.gov (United States)

    Grant, E.; Murdin, P.

    2000-11-01

    During the early Middle Ages (ca 500 to ca 1130) scholars with an interest in cosmology had little useful and dependable literature. They relied heavily on a partial Latin translation of PLATO's Timaeus by Chalcidius (4th century AD), and on a series of encyclopedic treatises associated with the names of Pliny the Elder (ca AD 23-79), Seneca (4 BC-AD 65), Macrobius (fl 5th century AD), Martianus ...

  2. Laser Cosmology

    OpenAIRE

    Chen, Pisin

    2014-01-01

    Recent years have seen tremendous progress in our understanding of the cosmos, which in turn points to even deeper questions to be further addressed. Concurrently the laser technology has undergone dramatic revolutions, providing exciting opportunity for science applications. History has shown that the symbiosis between direct observations and laboratory investigation is instrumental in the progress of astrophysics. We believe that this remains true in cosmology. Current frontier phenomena re...

  3. Extended Cosmologies

    CERN Document Server

    Capozziello, S; Fatibene, L; Ferraris, M; Garruto, S

    2016-01-01

    We shall discuss cosmological models in extended theories of gravitation. We shall define a surface, called the model surface, in the space of observable parameters which characterises families of theories. We also show how this surface can be used to compare with observations. The model surface can potentially be used to falsify whole families of models instead reasoning on a single model basis as it is usually done by best fit arguments with observations.

  4. Chandra Observations of SNR RCW 103

    OpenAIRE

    Frank, Kari A.; Burrows, David N.; Park, Sangwook

    2015-01-01

    We analyze three Chandra observations, with a combined exposure time of 99 ks, of the Galactic supernova remnant RCW 103, a young supernova remnant, previously with no clear detection of metal-rich ejecta. Based on our imaging and spectral analyses of these deep Chandra data, we find evidence for metal-rich ejecta emission scattered throughout the remnant. X-ray emission from the shocked ejecta is generally weak, and the shocked circumstellar medium (CSM) is a largely dominant component acros...

  5. The Evolution of Cluster Substructure

    CERN Document Server

    Jeltema, T E; Bautz, M W; Buote, D A; Jeltema, Tesla E.; Canizares, Claude R.; Bautz, Mark W.; Buote, David A.

    2003-01-01

    Using Chandra archival data, we have begun a study to quantify the evolution of cluster morphology with redshift. To quantify cluster morphology, we use the power ratio method developed by Buote and Tsai (1995). Power ratios are constructed from moments of the two-dimensional gravitational potential and are, therefore, related to a cluster's dynamical state. Our sample will include around 50 clusters from the Chandra archive with redshifts between 0.11 and 1.1. These clusters were selected from two fairly complete flux-limited X-ray surveys (the ROSAT Bright Cluster Sample and the Einstein Medium Sensitivity Survey), and additional high-redshift clusters were selected from recent ROSAT flux-limited surveys. Here we present preliminary results from the first 15 clusters in this sample. Of these, eight have redshifts below 0.5, and seven have redshifts above 0.5.

  6. String Gas Cosmology

    OpenAIRE

    Brandenberger, Robert H.

    2008-01-01

    String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the curren...

  7. Morphology parameters: substructure identification in X-ray galaxy clusters

    Science.gov (United States)

    Parekh, Viral; van der Heyden, Kurt; Ferrari, Chiara; Angus, Garry; Holwerda, Benne

    2015-03-01

    Context. In recent years multi-wavelength observations have shown the presence of substructures related to merging events in a large proportion of galaxy clusters. Clusters can be roughly grouped into two categories - relaxed and non-relaxed - and a proper characterisation of the dynamical state of these systems is crucial for both astrophysical and cosmological studies. Aims: In this paper we investigate the use of a number of morphological parameters (Gini, M20, concentration, asymmetry, smoothness, ellipticity, and Gini of the second-order moment, GM) introduced to automatically classify clusters as relaxed or dynamically disturbed systems. Methods: We apply our method to a sample of clusters at different redshifts extracted from the Chandra archive and investigate possible correlations between morphological parameters and other X-ray gas properties. Results: We conclude that a combination of the adopted parameters is a very useful tool for properly characterising the X-ray cluster morphology. According to our results, three parameters - Gini, M20, and concentration - are very promising for identifying cluster mergers. The Gini coefficient is a particularly powerful tool, especially at high redshift, because it is independent of the choice of the position of the cluster centre. We find that high Gini (>0.65), high concentration (>1.55), and low M20 (-1.4) characterise dynamically perturbed systems. We also estimate the X-ray cluster morphological parameters in the case of radio loud clusters. Since they are in excellent agreement with previous analyses we confirm that diffuse intracluster radio sources are associated with major mergers. Appendix A is available in electronic form at http://www.aanda.org

  8. Religion, theology and cosmology

    Directory of Open Access Journals (Sweden)

    John T. Fitzgerald

    2013-10-01

    Full Text Available Cosmology is one of the predominant research areas of the contemporary world. Advances in modern cosmology have prompted renewed interest in the intersections between religion, theology and cosmology. This article, which is intended as a brief introduction to the series of studies on theological cosmology in this journal, identifies three general areas of theological interest stemming from the modern scientific study of cosmology: contemporary theology and ethics; cosmology and world religions; and ancient cosmologies. These intersections raise important questions about the relationship of religion and cosmology, which has recently been addressed by William Scott Green and is the focus of the final portion of the article.

  9. Chemical cosmology

    CERN Document Server

    Boeyens, Jan CA

    2010-01-01

    The composition of the most remote objects brought into view by the Hubble telescope can no longer be reconciled with the nucleogenesis of standard cosmology and the alternative explanation, in terms of the LAMBDA-Cold-Dark-Matter model, has no recognizable chemical basis. A more rational scheme, based on the chemistry and periodicity of atomic matter, opens up an exciting new interpretation of the cosmos in terms of projective geometry and general relativity. The response of atomic structure to environmental pressure predicts non-Doppler cosmical redshifts and equilibrium nucleogenesis by alp

  10. Rastall cosmology

    CERN Document Server

    Fabris, J C; Rodrigues, D C; Batista, C E M; Daouda, M H

    2012-01-01

    We review the difficulties of the generalized Chaplygin gas model to fit observational data, due to the tension between background and perturbative tests. We argue that such issues may be circumvented by means of a self-interacting scalar field representation of the model. However, this proposal seems to be successful only if the self-interacting scalar field has a non-canonical form. The latter can be implemented in Rastall's theory of gravity, which is based on a modification of the usual matter conservation law. We show that, besides its application to the generalized Chaplygin gas model, other cosmological models based on Rastall's theory have many interesting and unexpected new features.

  11. Astrophysical cosmology

    Science.gov (United States)

    Bardeen, J. M.

    The last several years have seen a tremendous ferment of activity in astrophysical cosmology. Much of the theoretical impetus has come from particle physics theories of the early universe and candidates for dark matter, but what promise to be even more significant are improved direct observations of high z galaxies and intergalactic matter, deeper and more comprehensive redshift surveys, and the increasing power of computer simulations of the dynamical evolution of large scale structure. Upper limits on the anisotropy of the microwave background radiation are gradually getting tighter and constraining more severely theoretical scenarios for the evolution of the universe.

  12. The Chandra Carina Complex Project View of Trumpler 16

    CERN Document Server

    Wolk, Scott J; Getman, Konstantin V; Feigelson, Eric D; Preibisch, Thomas; Townsley, Leisa K; Wang, Junfeng; Stassun, Keivan G; King, Robert R; McCaughrean, Mark J; Moffat, Anthony F J; Zinnecker, Hans

    2011-01-01

    Trumpler 16 is a well--known rich star cluster containing the eruptive supergiant $\\eta$ Carin\\ae\\ and located in the Carina star-forming complex. In the context of the Chandra Carina Complex Project, we study Trumpler 16 using new and archival X-ray data. A revised X-ray source list of the Trumpler 16 region contains 1232 X-ray sources including 1187 likely Carina members. These are matched to 1047 near-infrared counterparts detected by the HAWK-I instrument at the VLT allowing for better selection of cluster members. The cluster is irregular in shape. Although it is roughly circular, there is a high degree of sub-clustering, no noticeable central concentration and an extension to the southeast. The high--mass stars show neither evidence of mass segregation nor evidence of strong differential extinction. The derived power-law slope of the X-ray luminosity function for Trumpler 16 reveals a much steeper function than the Orion Nebula Cluster implying different ratio of solar- to higher-mass stars. We estimate...

  13. Cosmological tests of modified gravity.

    Science.gov (United States)

    Koyama, Kazuya

    2016-04-01

    We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard [Formula: see text]CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years. PMID:27007681

  14. Cosmology with a time dependent cosmological constant

    International Nuclear Information System (INIS)

    In the context of the scalar-tensor theories we consider cosmological models with a time dependent cosmological constant. Several toy models are obtained among them there are solutions without singularity and accelerating. (Author)

  15. Symmetron Cosmology

    CERN Document Server

    Hinterbichler, Kurt; Levy, Aaron; Matas, Andrew

    2011-01-01

    The symmetron is a scalar field associated with the dark sector whose coupling to matter depends on the ambient matter density. The symmetron is decoupled and screened in regions of high density, thereby satisfying local constraints from tests of gravity, but couples with gravitational strength in regions of low density, such as the cosmos. In this paper we derive the cosmological expansion history in the presence of a symmetron field, tracking the evolution through the inflationary, radiation- and matter-dominated epochs, using a combination of analytical approximations and numerical integration. For a broad range of initial conditions at the onset of inflation, the scalar field reaches its symmetry-breaking vacuum by the present epoch, as assumed in the local analysis of spherically-symmetric solutions and tests of gravity. For the simplest form of the potential, the energy scale is too small for the symmetron to act as dark energy, hence we must add a cosmological constant to drive late-time cosmic acceler...

  16. Cascading Cosmology

    CERN Document Server

    Agarwal, Nishant; Khoury, Justin; Trodden, Mark

    2009-01-01

    We develop a fully covariant, well-posed 5D effective action for the 6D cascading gravity brane-world model, and use this to study cosmological solutions. We obtain this effective action through the 6D decoupling limit, in which an additional scalar degree mode, \\pi, called the brane-bending mode, determines the bulk-brane gravitational interaction. The 5D action obtained this way inherits from the sixth dimension an extra \\pi self-interaction kinetic term. We compute appropriate boundary terms, to supplement the 5D action, and hence derive fully covariant junction conditions and the 5D Einstein field equations. Using these, we derive the cosmological evolution induced on a 3-brane moving in a static bulk. We study the strong- and weak-coupling regimes analytically in this static ansatz, and perform a complete numerical analysis of our solution. Although the cascading model can generate an accelerating solution in which the \\pi field comes to dominate at late times, the presence of a critical singularity prev...

  17. Newtonian cosmology - Problems of cosmological didactics

    Energy Technology Data Exchange (ETDEWEB)

    Skarzynski, E.

    1983-03-01

    The article presents different methods of model construction in Newtonian cosmology. Newtonian cosmology is very convenient for discussion of local problems, so the problems presented are of great didactic importance. The constant k receives a new interpretation in relativistic cosmology as the curvature of the space in consequence of the greater informational capacity of Riemann space in comparison to Euclidean space. 11 references.

  18. H$_{0}$ and odds on cosmology

    CERN Document Server

    Jaffe, A

    1995-01-01

    Recent observations by the Hubble Space Telescope of Cepheids in the Virgo cluster imply a Hubble Constant H_0=80\\pm17\\ km/sec/Mpc. We attempt to clarify some issues of interpretation of these results for determining the global cosmological parameters \\Omega and \\Lambda. Using the formalism of Bayesian model comparison, the data suggest a universe with a nonzero cosmological constant \\Lambda>0, but vanishing curvature: \\Omega+\\Lambda=1.

  19. A natural cosmological constant from chameleons

    Energy Technology Data Exchange (ETDEWEB)

    Nastase, Horatiu, E-mail: nastase@ift.unesp.br [Instituto de Física Teórica, UNESP-Universidade Estadual Paulista, R. Dr. Bento T. Ferraz 271, Bl. II, Sao Paulo 01140-070, SP (Brazil); Weltman, Amanda, E-mail: amanda.weltman@uct.ac.za [Astrophysics, Cosmology & Gravity Center, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7700 (South Africa)

    2015-07-30

    We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)

  20. Cosmological Parameters and Black Holes

    CERN Document Server

    Harun-al-Rashid, S M

    2002-01-01

    This work is related to different questions within cosmology. The principal idea herein is to develop cosmological knowledge making use of the analyses of observational data in order to find the values of the matter density Omega_m and vacuum energy density Omega_Lambda. Data fitting is carried out using two statistical methods, chi^2 and maximum likelihood. The data analysis exhibits that a low density and flat Universe is strongly favoured. Applying the Omega_m value found for clusters of galaxies, we demonstrate that clusters have very little room for baryonic dark matter. An upper limit to the small but non-negligible sum of baryonic dark matter and galaxy mass can be estimated, requiring the use of special statistics. A Toroidal Black Hole (TBH) study, in contrast to the Spherical Black Hole (SBH), shows that the TBH can be used as an important tool in explaining AGN phenomena.

  1. Catching a Galactic Football: Chandra Examines Cygnus A

    Science.gov (United States)

    2000-11-01

    falling into the Cygnus A galaxy. However, the two jets powered by the nuclear black hole in this galaxy push this gas outward, like a balloon being inflated by a tank of gas. Cygnus A is not alone in its galactic neighborhood, but is a member of a large cluster containing many galaxies. Extremely hot (tens of millions of degrees Celsius) gas is spread between the galaxies. Although it has a very low density, this gas provides enough resistance to slow down the outward advancement of the particle jets from Cygnus A. At the ends of the jets, astronomers find bright areas of radio and X-ray emission known as "hot spots." Scientists believe that fast atomic particles and magnetic fields from the jets spill out into the region, providing pressure that continuously inflates the cavity. In a paper accepted by the Astrophysical Journal Letters, Wilson, Young and Shopbell discuss how the Chandra observations resolve a long-standing puzzle about the hot spots at the ends of the jets. By analyzing the X-ray emission of the hot spots, the astronomers have measured the strength of the magnetic field associated with them. "The radio data themselves cannot determine the strength of the magnetic field, a limitation that has inhibited progress in our understanding of cosmic radio sources for 50 years," said Wilson. "Combination of the Chandra X-ray and the radio data allows a quite precise measurement of the field strength." The Chandra observation of Cygnus A was made with the ACIS on May 21, 2000, for over nine hours. The ACIS X-ray camera was developed for NASA by Pennsylvania State University and MIT. NASA's Marshall Space Flight Center in Huntsville, AL, manages the Chandra program. TRW, Inc., Redondo Beach, California, is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, MA. This research was supported by the Chandra project at the NASA Marshall Space Flight Center. Images associated with this

  2. Chandra Sees Shape of Universe During Formative, Adolescent Years

    Science.gov (United States)

    2003-03-01

    Scientists using NASA's Chandra X-ray Observatory have taken a snapshot of the adolescent universe from about five billion years ago when the familiar web-like structure of galaxy chains and voids first emerged. The observation reveals distant and massive galaxies dotting the sky, clustered together under the gravitational attraction of deep, unseen pockets of dark matter. This provides important clues of how the universe matured from its chaotic beginnings to its elegant structure we see today. These results are presented today in a press conference at the meeting of the High Energy Astrophysics Division of the American Astronomical Society at Mt. Tremblant, Quebec. "Piece by piece, we are assembling a photo album of the universe through the ages," said Yuxuan Yang, a doctorate candidate at the University of Maryland, College Park, who conducted the analysis. "Last month we saw a picture of the infant universe taken with the Wilkinson Microwave Anisotropy Probe. Now we can add a snapshot of its adolescence." The Chandra observation traced a patch of sky known as the Lockman Hole in the constellation Ursa Major (containing the Big Dipper). Chandra saw a rich density of active galaxies, seven times denser than what has been detected in previous optical and radio surveys at similar distances. This provides the clearest picture yet at the large-scale structure of the universe at such distances (and age), according to Dr. Richard Mushotzky of NASA Goddard Space Flight Center in Greenbelt, Md., who led the observation. Lockman Hole JPEG, TIFF, PS An image that has been "blurred" to allow better view of the structures outlined by the X-ray sources. The color represents the spectra of the AGN. The red color indicates the sources on average radiates at longer wavelength while green and blue colors indicates the sources radiates at shorter wavelength. The Green and blue regions appear to form a wall, or shows more lumpiness than the "red" sources. If one could capture the

  3. Negative Energy Cosmology and the Cosmological Constant

    CERN Document Server

    Prokopec, Tomislav

    2011-01-01

    It is well known that string theories naturally compactify on anti-de Sitter spaces, and yet cosmological observations show no evidence of a negative cosmological constant in the early Universe's evolution. In this letter we present two simple nonlocal modifications of the standard Friedmann cosmology that can lead to observationally viable cosmologies with an initial (negative) cosmological constant. The nonlocal operators we include are toy models for the quantum cosmological backreaction. In Model I an initial quasiperiodic oscillatory epoch is followed by inflation and a late time matter era, representing a dark matter candidate. The backreaction in Model II quickly compensates the negative cosmological term such that the Ricci curvature scalar rapidly approaches zero, and the Universe ends up in a late time radiation era.

  4. THE CHEMICAL SIGNATURE OF A RELIC STAR CLUSTER IN THE SEXTANS DWARF SPHEROIDAL GALAXY-IMPLICATIONS FOR NEAR-FIELD COSMOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Karlsson, Torgny [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Bland-Hawthorn, Joss [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Freeman, Ken C. [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston ACT 2611 (Australia); Silk, Joe, E-mail: torgny.karlsson@physics.uu.se [Physics Department, University of Oxford, Oxford OX1 3RH (United Kingdom)

    2012-11-10

    We present tentative evidence for the existence of a dissolved star cluster at [Fe/H] = -2.7 in the Sextans dwarf spheroidal galaxy. We use the technique of chemical tagging to identify stars that are highly clustered in a multi-dimensional chemical abundance space (C-space). In a sample of six stars, three, possibly four, stars are identified as potential cluster stars. The initial stellar mass of the parent cluster is estimated from two independent observations to be M{sub *,init}=1.9{sup +1.5}{sub -0.9}(1.6{sup +1.2}{sub -0.8}) Multiplication-Sign 10{sup 5} M{sub sun}, assuming a Salpeter (Kroupa) initial mass function. If corroborated by follow-up spectroscopy, this star cluster is the most metal-poor system identified to date. Chemical signatures of remnant clusters in dwarf galaxies like Sextans provide us with a very powerful probe to the high-redshift universe. From available observational data, we argue that the average star cluster mass in the majority of the newly discovered ultra-faint dwarf galaxies was notably lower than it is in the Galaxy today and possibly lower than in the more luminous, classical dwarf spheroidal galaxies. Furthermore, the mean cumulative metallicity function of the dwarf spheroidals falls below that of the ultra-faints, which increases with increasing metallicity as predicted from our stochastic chemical evolution model. These two findings, together with a possible difference in the ([Mg/Fe]) ratio suggest that the ultra-faint dwarf galaxy population, or a significant fraction thereof, and the dwarf spheroidal population were formed in different environments and would thus be distinct in origin.

  5. On an Alternative Cosmology

    CERN Document Server

    Vankov, A

    1998-01-01

    The suggested alternative cosmology is based on the idea of barion symmetric universe, in which our home universe is a representative of multitude of typical matter and antimatter universes. This alternative concept gives a physically reasonable explanation of all major problems of the Standard Cosmological Model. Classification Code MSC: Cosmology 524.8 Key words: standard cosmological model, alternative cosmology, barionic symmetry, typical universe, quasars, cosmic rays.

  6. Inhomogeneous Cosmology Redux

    CERN Document Server

    Moffat, J W

    2016-01-01

    An alternative to the postulate of dark energy required to explain the accelerated expansion of the universe is to adopt an inhomogeneous cosmological model to explain the supernovae data without dark energy. We adopt a void cosmology model, based on the inhomogeneous Lema\\^{i}tre-Tolman-Bondi solution of Einstein's field equations. The model can resolve observational anomalies in the $\\Lambda CDM$ model, such as the discrepancy between the locally measured value of the Hubble constant, $H_0=73.24\\pm 1.74\\,{\\rm km}\\,{\\rm s}^{-1}\\,{\\rm Mpc}^{-1}$, and the $H_0=66.93\\pm 0.62\\,{\\rm km}\\,{\\rm s}^{-1}\\,{\\rm Mpc}^{-1}$ determined by the Planck satellite data and the $\\Lambda CDM$ model, and the lithium $^{7}{\\rm Li}$ problem, which is a $5\\sigma$ mismatch between the theoretical prediction for the $^{7}{\\rm Li}$ from big bang nucleosynthesis and the value that we observe locally today at $z=0$. The void model can also resolve the tension between the number of massive clusters derived from the Sunyaev-Zel'dovich eff...

  7. The Chandra Survey of Extragalactic Sources in the 3CR Catalog: X-ray Emission from Nuclei, Jets, and Hotspots in the Chandra Archival Observations

    CERN Document Server

    Massaro, F; Liuzzo, E; Orienti, M; Paladino, R; Paggi, A; Tremblay, G R; Wilkes, B J; Kuraszkiewicz, J; Baum, S A; O'Dea, C P

    2016-01-01

    As part of our program to build a complete radio and X-ray database of all the 3CR extragalactic radio sources, we present an analysis of 93 sources for which Chandra archival data are available. Most of these sources have been already published. Here we provide a uniform re-analysis and present nuclear X-ray fluxes and X-ray emission associated with radio jet knots and hotspots using both publicly available radio images and new radio images that have been constructed from data available in the VLA archive. For about 1/3 of the sources in the selected sample a comparison between the Chandra and the radio observations was not reported in the literature: we find X-ray detections of 2 new radio jet knots and 17 hotspots. We also report the X-ray detection of extended emission from the intergalactic medium of 15 galaxy clusters, two of which were most likely unknown previously.

  8. Exploring Cosmology with Supernovae

    DEFF Research Database (Denmark)

    Li, Xue

    The most intriguing aspect of studying supernovae associated with gamma-ray bursts (GRB-SNe) is the fact that they are accompanied by the most energetic events in the universe: gamma-ray bursts (GRBs). GRBs are extremely bright, which makes a swift trigger of observation on them. Therefore, a sup...... of a cluster of galaxies. We also theoretically deduce time delay. The second Section is dedicated to SN. Progenitor models of different types of SNe are investigated. SNe Ia and their application as standard candles are discussed.......-SNe. They are a subclass of CC SNe. Light curves of GRB-SNe are obtained and their properties are studied. We ascertain that the properties of GRB-SNe make them another candidate for standardizable candles in measuring the cosmic distance. Cosmological parameters M and are constrained with the help of GRB-SNe. The first...

  9. Big Bangs in Galaxy Clusters: Using X-ray Temperature Maps to Trace Merger Histories in Clusters with Radio Halos/Relics

    Science.gov (United States)

    Burns, Jack O.; Datta, Abhirup; Hallman, Eric J.

    2016-06-01

    Galaxy clusters are assembled through large and small mergers which are the most energetic events ("bangs") since the Big Bang. Cluster mergers "stir" the intracluster medium (ICM) creating shocks and turbulence which are illuminated by ~Mpc-sized radio features called relics and halos. These shocks heat the ICM and are detected in x-rays via thermal emission. Disturbed morphologies in x-ray surface brightness and temperatures are direct evidence for cluster mergers. In the radio, relics (in the outskirts of the clusters) and halos (located near the cluster core) are also clear signposts of recent mergers. Our recent ENZO cosmological simulations suggest that around a merger event, radio emission peaks very sharply (and briefly) while the x-ray emission rises and decays slowly. Hence, a sample of galaxy clusters that shows both luminous x-ray emission and radio relics/halos are good candidates for very recent mergers. We are in the early stages of analyzing a unique sample of 48 galaxy clusters with (i) known radio relics and/or halos and (ii) significant archival x-ray observations (>50 ksec) from Chandra and/or XMM. We have developed a new x-ray data analysis pipeline, implemented on parallel processor supercomputers, to create x-ray surface brightness, high fidelity temperature, and pressure maps of these clusters in order to study merging activity. The temperature maps are made using three different map-making techniques: Weighted Voronoi Tessellation, Adaptive Circular Binning, and Contour Binning. In this talk, we will show preliminary results for several clusters, including Abell 2744 and the Bullet cluster. This work is supported by NASA ADAP grant NNX15AE17G.

  10. A NEW METHOD TO QUANTIFY X-RAY SUBSTRUCTURES IN CLUSTERS OF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Andrade-Santos, Felipe; Lima Neto, Gastao B.; Lagana, Tatiana F. [Departamento de Astronomia, Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Geofisica e Ciencias Atmosfericas, Rua do Matao 1226, Cidade Universitaria, 05508-090 Sao Paulo, SP (Brazil)

    2012-02-20

    We present a new method to quantify substructures in clusters of galaxies, based on the analysis of the intensity of structures. This analysis is done in a residual image that is the result of the subtraction of a surface brightness model, obtained by fitting a two-dimensional analytical model ({beta}-model or Sersic profile) with elliptical symmetry, from the X-ray image. Our method is applied to 34 clusters observed by the Chandra Space Telescope that are in the redshift range z in [0.02, 0.2] and have a signal-to-noise ratio (S/N) greater than 100. We present the calibration of the method and the relations between the substructure level with physical quantities, such as the mass, X-ray luminosity, temperature, and cluster redshift. We use our method to separate the clusters in two sub-samples of high- and low-substructure levels. We conclude, using Monte Carlo simulations, that the method recuperates very well the true amount of substructure for small angular core radii clusters (with respect to the whole image size) and good S/N observations. We find no evidence of correlation between the substructure level and physical properties of the clusters such as gas temperature, X-ray luminosity, and redshift; however, analysis suggest a trend between the substructure level and cluster mass. The scaling relations for the two sub-samples (high- and low-substructure level clusters) are different (they present an offset, i.e., given a fixed mass or temperature, low-substructure clusters tend to be more X-ray luminous), which is an important result for cosmological tests using the mass-luminosity relation to obtain the cluster mass function, since they rely on the assumption that clusters do not present different scaling relations according to their dynamical state.

  11. Six Years Into Its Mission, NASA's Chandra X-ray Observatory Continues to Achieve Scientific Firsts

    Science.gov (United States)

    2005-08-01

    facing away from Earth's space satellites. Another Chandra discovery -- gleaned from the deepest X-ray observation of any star cluster -- offered insights on Earth's survival in its infancy. Chandra s focus was the Orion Nebula, which contains at least 1,400 young stars, 30 that are prototypes of the early sun. Using Chandra, scientists learned these young stars produce violent X-ray flares much more frequently and energetically than anything seen today from our 4.6 billion-year-old sun. This implies super-flares torched our young solar system and likely affected the planet-forming disk around the early sun -- enhancing the survival chances of Earth. Space is a harsh environment with extreme temperatures, harmful radiation and none of the protection offered by Earth s atmosphere, said Chandra Program Manager Keith Hefner of the Marshall Center. "Ironically, the fact that our atmosphere absorbs harmful X-rays is the very reason for Chandra s existence. Getting outside the absorbing atmosphere of the Earth requires space-based observatories, and viewing the universe in multiple wavelengths is necessary to fully study cosmic events. Chandra s continued outstanding performance after six years of operation under such harsh conditions is evidence that it is, indeed, an engineering marvel." In its sixth year, Chandra also continued to build on its growing list of discoveries involving black holes. This included finding the most powerful eruption seen in the universe, generated by a supermassive black hole growing at a remarkable rate. The eruption -- which has lasted for 100 million years and is still going -- has generated the energy equivalent to hundreds of millions of gamma-ray bursts. This discovery illustrated the enormous appetite of large black holes, and the profound impact they have on their surroundings. Other recent discoveries include confirming the existence of weight limits for supermassive black holes, finding evidence for a swarm of black holes near the

  12. Spectral analysis of the Chandra comet survey

    NARCIS (Netherlands)

    Bodewits, D.; Christian, D. J.; Torney, M.; Dryer, M.; Lisse, C. M.; Dennerl, K.; Zurbuchen, T. H.; Wolk, S. J.; Tielens, A. G. G. M.; Hoekstra, R.

    2007-01-01

    Aims. We present results of the analysis of cometary X-ray spectra with an extended version of our charge exchange emission model (Bodewits et al. 2006). We have applied this model to the sample of 8 comets thus far observed with the Chandra X-ray observatory and acis spectrometer in the 300 - 1000

  13. Chandra X-ray Observatory Optical Axis and Aimpoint

    Science.gov (United States)

    Zhao, Ping

    2016-01-01

    Chandra X-ray Observatory revolutionized the X-ray astronomy as being the first, and so far the only, X-ray telescope achieving sub-arcsecond resolution. Chandra comprises of three principal elements: the High Resolution Mirror Assembly (HRMA), Pointing Control and Aspect Determination (PCAD) system, and the Science Instrument Module (SIM). To achieve and retain the unprecedented imaging quality, it is critical that these three principal elements stay rigid and stable for the entire life time of the Chandra operation. Tracking the Chandra optical axis and aimpoint with respect to detector positions is the most relevant measurement for understanding telescope stability. The study shows that both the optical axis and the aimpoint has been drifting since Chandra launch. I will discuss the telescope focal-point, optical axis, aimpoint, their positiondrifts during the mission, the impact to Chandra operations, and the permanent default aimpoint, to be implemented in Chandra cycle 18.

  14. Chandra's Find of Lonely Halo Raises Questions About Dark Matter

    Science.gov (United States)

    2004-10-01

    Dark matter continues to confound astronomers, as NASA's Chandra X-ray Observatory demonstrated with the detection of an extensive envelope of dark matter around an isolated elliptical galaxy. This discovery conflicts with optical data that suggest a dearth of dark matter around similar galaxies, and raises questions about how galaxies acquire and keep such dark matter halos. The observed galaxy, known as NGC 4555, is unusual in that it is a fairly large, elliptical galaxy that is not part of a group or cluster of galaxies. In a paper to be published in the November 1, 2004 issue of the Monthly Notices of the Royal Astronomical Society, Ewan O'Sullivan of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA and Trevor Ponman of the University of Birmingham, United Kingdom, use the Chandra data to show that the galaxy is embedded in a cloud of 10-million-degree-Celsius gas. X-ray/Optical Composite of NGC 4555 X-ray/Optical Composite of NGC 4555 This hot gas cloud has a diameter of about 400,000 light years, about twice that of the visible galaxy. An enormous envelope, or halo, of dark matter is needed to confine the hot cloud to the galaxy. The total mass of the dark matter halo is about ten times the combined mass of the stars in the galaxy, and 300 times the mass of the hot gas cloud. A growing body of evidence indicates that dark matter - which interacts with itself and "normal" matter only through gravity - is the dominant form of matter in the universe. According to the popular "cold dark matter" theory, dark matter consists of mysterious particles left over from the dense early universe that were moving slowly when galaxies and galaxy clusters began to form. "The observed properties of NGC 4555 confirm that elliptical galaxies can posses dark matter halos of their own, regardless of their environment," said O'Sullivan. "This raises an important question: what determines whether elliptical galaxies have dark matter halos?" DSS Optical Image of NGC

  15. Cosmology and particle physics

    International Nuclear Information System (INIS)

    The author reviews the standard cosmology, focusing on primordial nucleosynthesis, and discusses how the standard cosmology has been used to place constraints on the properties of various particles. Baryogenesis is examined in which the B, C, CP violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and the present baryon-to-baryon ratio. Monoposes, cosmology and astrophysics are reviewed. The author also discusses supersymmetry/supergravity and cosmology, superstrings and cosmology in extra dimensions, and axions, astrophics, and cosmology

  16. Hot plasma in clusters of galaxies, the largest objects in the universe

    CERN Document Server

    Sarazin, C L

    2003-01-01

    Clusters of galaxies are the largest organized structures in the Universe. They are important cosmological probes, since they are large enough to contain a fair sample of the materials in the Universe, but small enough to have achieved dynamical equilibrium. Clusters were first discovered as concentrations of hundreds of bright galaxies in a region about 3 megaparsecs (10 million light years) across. However, the dominant observed form of matter in clusters is hot, diffuse intergalactic gas. This intracluster plasma has typical temperatures of T ~ 7e7 K, and typical electron densities of n_e ~ 10^{-3} cm^{-3}. This intracluster plasma mainly emits X-rays, and typical cluster X-ray luminosities are L_X ~ 10^{43} - 10^{45} erg/s. The basic properties of and physical processes in the intracluster plasma will be reviewed. Important observational constraints on plasma processes in these systems will be discussed. Recent X-ray observations of clusters of galaxies with the orbiting Chandra X-ray Observatory will be ...

  17. The convergence fluctuation of light by clusters of galaxies - a cosmological test using the second acoustic peak of the microwave background

    CERN Document Server

    Lieu, R

    2004-01-01

    The weak lensing magnification of distant light by clusters of galaxies, assumed to be virialized systems with an NFW density profile, was calculated analytically as a statistical average over a random non-evolving distribution within $z=1$. The effect is exactly cancelled by the Dyer-Roeder beam in between clusters - this conclusion is valid also for an ensemble of spherical clumps of arbitrary density profile. An analytical expression for the variance in the mean magnification is provided, using the general formula from our previous work. The all sky fluctuation in the angular size of the microwave background second acoustic peak, due to the random placement of cluster lenses in the intervening space, is then derived to be $\\approx$ 33 %. Moreover, this standard deviation corresponds to that of a highly skewed magnification distribution, with a long tail extending towards the side of positive magnification, since any negative excursion from the mean cannot cross the hard limit imposed by the Dyer-Roeder emp...

  18. Questions of Modern Cosmology Galileo's Legacy

    CERN Document Server

    D'Onofrio, Mauro

    2009-01-01

    Are we living in the "golden age" of cosmology? Are we close to understanding the nature of the unknown ingredients of the currently most accepted cosmological model and the physics of the early Universe? Or are we instead approaching a paradigm shift? What is dark matter and does it exist? How is it distributed around galaxies and clusters? Is the scientific community open to alternative ideas that may prompt a new scientific revolution - as the Copernican revolution did in Galileo's time? Do other types of supernovae exist that can be of interest for cosmology? Why have quasars never been effectively used as standard candles? Can you tell us about the scientific adventure of COBE? How does the extraction of the Cosmic Microwave Background anisotropy depend on the subtraction of the various astrophysical foregrounds? These, among many others, are the astrophysical, philosophical and sociological questions surrounding modern cosmology and the scientific community that Mauro D'Onofrio and Carlo Burigana pose t...

  19. Unimodular-Mimetic Cosmology

    CERN Document Server

    Nojiri, S; Oikonomou, V K

    2016-01-01

    We combine the unimodular gravity and mimetic gravity theories into a unified theoretical framework, which is proposed to solve the cosmological constant problem and the dark matter issue. After providing the formulation of the unimodular mimetic gravity and investigating all the new features that the vacuum unimodular gravity implies, by using the underlying reconstruction method, we realize some well known cosmological evolutions, with some of these being exotic for the ordinary Einstein-Hilbert gravity. Specifically we provide the vacuum unimodular mimetic gravity description of the de Sitter cosmology, of the perfect fluid with constant equation of state cosmology, of the Type IV singular cosmology and of the $R^2$ inflation cosmology. Moreover, we investigate how cosmologically viable cosmologies, which are compatible with the recent observational data, can be realized by the vacuum unimodular mimetic gravity. Since in some cases, the graceful exit from inflation problem might exist, we provide a qualita...

  20. Cosmological Evolution of Linear Bias

    CERN Document Server

    Basilakos, S; Basilakos, Spyros; Plionis, Manolis

    2000-01-01

    Using linear perturbation theory and the Friedmann-Lemaitre solutions of the cosmological field equations, we derive analytically a second-order differential equation for the evolution of the linear bias factor, b(z), between the background matter and a mass-tracer fluctuation field. We find b(z) to be a strongly dependent function of redshift in all cosmological models. Comparing our analytical solution with the semi-analytic model of Mo & White, which utilises the Press-Schechter formalism and the gravitationally induced evolution of clustering, we find an extremely good agreement even at large redshifts, once we normalize to the same bias value at two different epochs, one of which is the present. Furthermore, our analytic b(z) function agrees well with the outcome of N-body simulations even up to large redshifts.

  1. Cosmological magnetic fields

    Indian Academy of Sciences (India)

    Roy Maartens

    2000-10-01

    Magnetic fields are observed not only in stars, but in galaxies, clusters, and even high redshift Lyman- systems. In principle, these fields could play an important role in structure formation and also affect the anisotropies in the cosmic microwave background radiation (CMB). The study of cosmological magnetic fields aims not only to quantify these effects on large-scale structure and the CMB, but also to answer one of the outstanding puzzles of modern cosmology: when and how do magnetic fields originate? They are either primordial, i.e. created before the onset of structure formation, or they are generated during the process of structure formation itself.

  2. Cosmological Black Holes

    OpenAIRE

    Stornaiolo, Cosimo

    2001-01-01

    In this paper we propose a model for the formation of the cosmological voids. We show that cosmological voids can form directly after the collapse of extremely large wavelength perturbations into low-density black holes or cosmological black holes (CBH). Consequently the voids are formed by the comoving expansion of the matter that surrounds the collapsed perturbation. It follows that the universe evolves, in first approximation, according to the Einstein-Straus cosmological model. We discuss...

  3. Introduction to cosmology

    CERN Document Server

    Roos, Matts

    2015-01-01

    The Fourth Edition of Introduction to Cosmology provides a concise, authoritative study of cosmology at an introductory level. Starting from elementary principles and the early history of cosmology, the text carefully guides the student on to curved spacetimes, special and general relativity, gravitational lensing, the thermal history of the Universe, and cosmological models, including extended gravity models, black holes and Hawking's recent conjectures on the not-so-black holes.

  4. Particle physics and cosmology

    International Nuclear Information System (INIS)

    During the past year, the research of the members of our group has spanned virtually all the topics at the interface of cosmology and particle physics: inflationary Universe scenarios, astrophysical and cosmological constraints on particle properties, ultra-high energy cosmic ray physics, quantum field theory in curved space-time, cosmology with extra dimensions, superstring cosmology, neutrino astronomy with large, underground detectors, and the formation of structure in the Universe

  5. White Dwarfs Cosmological and Galactic Probes

    CERN Document Server

    Sion, Edward M; Vennes, Stéphane

    2005-01-01

    The emphasis on white dwarf stars and cosmology arises from the most recent advances in cosmological and galactic structure research in which white dwarf stars are playing a very prominent role. Examples are Type Ia supernovae (i.e. white dwarf supernovae), the origin and evolution of the universe, the age of the galactic disk, cosmochronology using white dwarfs in globular clusters and galactic clusters, and the physics of accretion onto compact (very dense) stars. As an assisting guide to the reader, we have included, by invitation, comprehensive review articles in each of the four major areas of the book, white dwarf supernovae, cosmology, accretion physics and galactic structure. The reviews include introductory material that they build upon. The book is suitable and most useful to advanced undergraduates, graduate students and scientific professionals (e.g. astronomers, astrophysicists, cosmologists, physicists).

  6. Chandra Finds Well-Established Black Holes In Distant Quasars

    Science.gov (United States)

    2002-03-01

    University of Arizona and her colleagues disagree. In addition to the three distant Sloan quasars, they observed 14 other quasars with distances between 12 and 12.5 billion light years. Bechtold's group looked at their larger sample to determine that the younger, more distant quasars were radiating a lower percentage of their energy in X-rays. "The X-ray data are consistent with predictions of some theories that a hot gas atmosphere is associated with the accretion disk swirling around a central supermassive black hole," said Bechtold, provided the distant quasars have more massive black holes than nearby ones. "These theories predict that large supermassive black holes should be relatively weaker X-ray emittters than smaller ones, which is what we observed with Chandra." All groups agreed that the masses of the black holes producing the X-rays are huge, given their relative youth. By various estimates, the three quasars each weighed in at between one and 10 billion times the mass of the Sun. By comparison, the black hole at the center of the Milky Way is believed to contain the mass equivalent to only about 3 million Suns. Daniel Schwartz of the Harvard-Smithsonian Center for Astrophysics took a different approach to the same data. In addition to looking at the quasars themselves, he examined the space around them. His search paid off with the discovery of a new X-ray source, which may be only about half a million light years away from the quasar SDSS 1306+0356 "It's not clear what the source is," said Schwartz. "One plausible explanation is that it is due to a high-energy jet of material ejected by the quasar over at least several hundred thousand years." Chandra has detected a number of such jets, which could be generated by the extraction of energy from the rotation of a supermassive black hole. In addition to SDSS 1306+0356, which has a cosmological redshift z = 5.99, the other distant Sloan Digital Sky Survey quasars observed in this study are SDSS 0836+0054 (redshift

  7. Summary of cosmology workshop

    Indian Academy of Sciences (India)

    Tarun Sandeep

    2004-10-01

    Cosmology is passing through a golden phase of rapid advance. The cosmology workshop at ICGC-2004 attracted a large number of research contributions to diverse topics of cosmology. I attempt to classify and summarize the research work and results of the oral and poster presentations made at the meeting.

  8. The Evolution of Cluster Substructure with Redshift

    CERN Document Server

    Jeltema, T E; Bautz, M W; Buote, D A; Jeltema, Tesla E.; Canizares, Claude R.; Bautz, Mark W.; Buote, David A.

    2003-01-01

    Using Chandra archival data, we quantify the evolution of cluster morphology with redshift. To quantify cluster morphology, we use the power ratio method developed by Buote and Tsai (1995). Power ratios are constructed from moments of the two-dimensional gravitational potential and are, therefore, related to a cluster's dynamical state. Our sample will include 40 clusters from the Chandra archive with redshifts between 0.11 and 0.89. These clusters were selected from two fairly complete flux-limited X-ray surveys (the ROSAT Bright Cluster Sample and the Einstein Medium Sensitivity Survey), and additional high-redshift clusters were selected from recent ROSAT flux-limited surveys. Here we present preliminary results from the first 28 clusters in this sample. Of these, 16 have redshifts below 0.5, and 12 have redshifts above 0.5.

  9. Radio signature of cosmological structure formation shocks

    OpenAIRE

    Hoeft, Matthias; Brueggen, Marcus

    2006-01-01

    In the course of the formation of cosmological structures, large shock waves are generated in the intra-cluster medium. In analogy to processes in supernova remnants, these shock waves may generate a significant population of relativistic electrons which, in turn, produce observable synchrotron emission. The extended radio relics found at the periphery of several clusters and possibly also a fraction of radio halo emission may have this origin. Here we derive an analytic expression for (i) th...

  10. Efficient exploration of cosmology dependence in the EFT of LSS

    CERN Document Server

    Cataneo, Matteo; Senatore, Leonardo

    2016-01-01

    The most effective use of data from current and upcoming large scale structure~(LSS) and CMB observations requires the ability to predict the clustering of LSS with very high precision. The Effective Field Theory of Large Scale Structure (EFTofLSS) provides an instrument for performing analytical computations of LSS observables with the required precision in the mildly nonlinear regime. In this paper, we develop efficient implementations of these computations that allow for an exploration of their dependence on cosmological parameters. They are based on two ideas. First, once an observable has been computed with high precision for a reference cosmology, for a new cosmology the same can be easily obtained with comparable precision just by adding the difference in that observable, evaluated with much less precision. Second, most cosmologies of interest are sufficiently close to the Planck best-fit cosmology that observables can be obtained from a Taylor expansion around the reference cosmology. These ideas are ...

  11. Philosophical Roots of Cosmology

    Science.gov (United States)

    Ivanovic, M.

    2008-10-01

    We shall consider the philosophical roots of cosmology in the earlier Greek philosophy. Our goal is to answer the question: Are earlier Greek theories of pure philosophical-mythological character, as often philosophers cited it, or they have scientific character. On the bases of methodological criteria, we shall contend that the latter is the case. In order to answer the question about contemporary situation of the relation philosophy-cosmology, we shall consider the next question: Is contemporary cosmology completely independent of philosophical conjectures? The answer demands consideration of methodological character about scientific status of contemporary cosmology. We also consider some aspects of the relation contemporary philosophy-cosmology.

  12. TRW Ships NASA's Chandra X-ray Observatory To Kennedy Space Center

    Science.gov (United States)

    1999-04-01

    Two U.S. Air Force C-5 Galaxy transport planes carrying the observatory and its ground support equipment landed at Kennedy's Space Shuttle Landing Facility at 2:40 p.m. EST this afternoon. REDONDO BEACH, CA.--(Business Wire)--Feb. 4, 1999--TRW has shipped NASA's Chandra X-ray Observatory ("Chandra") to the Kennedy Space Center (KSC), in Florida, in preparation for a Space Shuttle launch later this year. The 45-foot-tall, 5-ton science satellite will provide astronomers with new information on supernova remnants, the surroundings of black holes, and other celestial phenomena that produce vast quantities of X-rays. Cradled safely in the cargo hold of a tractor-trailer rig called the Space Cargo Transportation System (SCTS), NASA's newest space telescope was ferried on Feb. 4 from Los Angeles International Airport to KSC aboard an Air Force C-5 Galaxy transporter. The SCTS, an Air Force container, closely resembles the size and shape of the Shuttle cargo bay. Over the next few months, Chandra will undergo final tests at KSC and be mated to a Boeing-provided Inertial Upper Stage for launch aboard Space Shuttle Columbia. A launch date for the Space Shuttle STS-93 mission is expected to be announced later this week. The third in NASA's family of Great Observatories that includes the Hubble Space Telescope and the TRW-built Compton Gamma Ray observatory, Chandra will use the world's most powerful X-ray telescope to allow scientists to "see" and monitor cosmic events that are invisible to conventional optical telescopes. Chandra's X-ray images will yield new insight into celestial phenomena such as the temperature and extent of gas clouds that comprise clusters of galaxies and the superheating of gas and dust particles as they swirl into black holes. A TRW-led team that includes the Eastman Kodak Co., Raytheon Optical Systems Inc., and Ball Aerospace & Technologies Corp. designed and built the Chandra X-ray Observatory for NASA's Marshall Space Flight Center. The

  13. Investigating the cores of fossil systems with Chandra

    CERN Document Server

    Bharadwaj, V; Sanders, J S; Schellenberger, G

    2016-01-01

    We investigate the cores of fossil galaxy groups and clusters (`fossil systems') using archival Chandra data for a sample of 17 fossil systems. We determined the cool-core fraction for fossils via three observable diagnostics, the central cooling time, cuspiness, and concentration parameter. We quantified the dynamical state of the fossils by the X-ray peak/brightest cluster galaxy (BCG), and the X-ray peak/emission weighted centre separations. We studied the X-ray emission coincident with the BCG to detect the presence of potential thermal coronae. A deprojection analysis was performed for z < 0.05 fossils to obtain cooling time and entropy profiles, and to resolve subtle temperature structures. We investigated the Lx-T relation for fossils from the 400d catalogue to see if the scaling relation deviates from that of other groups. Most fossils are identified as cool-core objects via at least two cool-core diagnostics. All fossils have their dominant elliptical galaxy within 50 kpc of the X-ray peak, and mo...

  14. Radio Relics in Cosmological Simulations

    Indian Academy of Sciences (India)

    M. Hoeft; S. E. Nuza; S. Gottlöber; R. J. van Weeren; H. J. A. Röttgering; M. Brüggen

    2011-12-01

    Radio relics have been discovered in many galaxy clusters. They are believed to trace shock fronts induced by cluster mergers. Cosmological simulations allow us to study merger shocks in detail since the intra-cluster medium is heated by shock dissipation. Using high resolution cosmological simulations, identifying shock fronts and applying a parametric model for the radio emission allows us to simulate the formation of radio relics. We analyze a simulated shock front in detail. We find a rather broad Mach number distribution. The Mach number affects strongly the number density of relativistic electrons in the downstream area, hence, the radio luminosity varies significantly across the shock surface. The abundance of radio relics can be modeled with the help of the radio power probability distribution which aims at predicting radio relic number counts. Since the actual electron acceleration efficiency is not known, predictions for the number counts need to be normalized by the observed number of radio relics. For the characteristics of upcoming low frequency surveys we find that about thousand relics are awaiting discovery.

  15. A scientific case for future X-ray Astronomy: Galaxy Clusters at high redshifts

    CERN Document Server

    Tozzi, Paolo

    2013-01-01

    Clusters of galaxies at high redshift (z>1) are vitally important to understand the evolution of the large scale structure of the Universe, the processes shaping galaxy populations and the cycle of the cosmic baryons, and to constrain cosmological parameters. After 13 years of operation of the Chandra and XMM-Newton satellites, the discovery and characterization of distant X-ray clusters is proceeding at a slow pace, due to the low solid angle covered so far, and the time-expensive observations needed to physically characterize their intracluster medium (ICM). At present, we know that at z>1 many massive clusters are fully virialized, their ICM is already enriched with metals, strong cool cores are already in place, and significant star formation is ongoing in their most massive galaxies, at least at z>1.4. Clearly, the assembly of a large and well characterized sample of high-z X-ray clusters is a major goal for the future. We argue that the only means to achieve this is a survey-optimized X-ray mission capa...

  16. A Very Deep Chandra Observation of Abell 2052: Bubbles, Shocks, and Sloshing

    CERN Document Server

    Blanton, E L; Clarke, T E; Sarazin, C L; McNamara, B R; Douglass, E M; McDonald, M

    2011-01-01

    We present first results from a very deep (~650 ksec) Chandra X-ray observation of Abell 2052, as well as archival VLA radio observations. The data reveal detailed structure in the inner parts of the cluster, including bubbles evacuated by the AGN's radio lobes, compressed bubble rims, filaments, and loops. Two concentric shocks are seen, and a temperature rise is measured for the innermost one. On larger scales, we report the first detection of an excess surface brightness spiral feature. The spiral has cooler temperatures, lower entropies, and higher abundances than its surroundings, and is likely the result of sloshing gas initiated by a previous cluster-cluster or sub-cluster merger. Initial evidence for previously unseen bubbles at larger radii related to earlier outbursts from the AGN is presented.

  17. Clustering, Cosmology and a New Era of Black Hole Demographics -- II. The Conditional Luminosity Functions of Type 2 and Type 1 Active Galactic Nuclei

    CERN Document Server

    Ballantyne, D R

    2016-01-01

    The orientation-based unification model of active galactic nuclei (AGNs) posits that the principle difference between obscured (Type 2) and unobscured (Type 1) AGNs is the line-of-sight into the central engine. If this model is correct than there should be no difference in many of the properties of AGN host galaxies (e.g., the mass of the surrounding dark matter haloes). However, recent clustering analyses of Type 1 and Type 2 AGNs have provided some evidence for a difference in the halo mass, in conflict with the orientation-based unified model. In this work, a method to compute the Conditional Luminosity Function (CLF) of Type 2 and Type 1 AGNs is presented. The CLF allows many fundamental halo properties to be computed as a function of AGN luminosity, which we apply to the question of the host halo masses of Type 1 and 2 AGNs. By making use of the total AGN CLF, the Type 1 X-ray luminosity function, and the luminosity-dependent Type 2 AGN fraction, the CLFs of Type 1 and 2 AGNs are calculated at $z\\approx ...

  18. Cosmological acceleration. Dark energy or modified gravity?

    International Nuclear Information System (INIS)

    We review the evidence for recently accelerating cosmological expansion or ''dark energy'', either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any constituent Dark Energy. If constituent Dark Energy does not exist, so that our universe is now dominated by pressure-free matter, Einstein gravity must be modified at low curvature. The vacuum symmetry of any Robertson-Walker universe then characterizes Dark Gravity as low- or high-curvature modifications of Einstein gravity. The dynamics of either kind of ''dark energy'' cannot be derived from the homogeneous expansion history alone, but requires also observing the growth of inhomogeneities. Present and projected observations are all consistent with a small fine tuned cosmological constant, but also allow nearly static Dark Energy or gravity modified at cosmological scales. The growth of cosmological fluctuations will potentially distinguish between static and ''dynamic'' ''dark energy''. But, cosmologically distinguishing the Concordance Model ΛCDM from modified gravity will require a weak lensing shear survey more ambitious than any now projected. Dvali-Gabadadze-Porrati low-curvature modifications of Einstein gravity may also be detected in refined observations in the solar system (Lue and Starkman) or at the intermediate Vainstein scale (Iorio) in isolated galaxy clusters. Dark Energy's epicyclic character, failure to explain the original Cosmic Coincidence (''Why so small now?'') without fine tuning, inaccessibility to laboratory or solar system tests, along with braneworld theories, now motivate future precision solar system, Vainstein-scale and cosmological-scale studies of Dark Gravity. (Orig.)

  19. A Chandra Observation of Abell 13: Investigating the Origin of the Radio Relic

    CERN Document Server

    Juett, Adrienne M; Clarke, Tracy E; Andernach, Heinz; Ehle, Matthias; Fujita, Yutaka; Kempner, Joshua C; Roy, Alan L; Rudnick, Lawrence; Slee, O Bruce

    2007-01-01

    We present results from the Chandra X-ray observation of Abell 13, a galaxy cluster that contains an unusual noncentral radio source, also known as a radio relic. This is the first pointed X-ray observation of Abell 13, providing a more sensitive study of the properties of the X-ray gas. The X-ray emission from Abell 13 is extended to the northwest of the X-ray peak and shows substructure indicative of a recent merger event. The cluster X-ray emission is centered on the bright galaxy H of Slee et al. 2001. We find no evidence for a cooling flow in the cluster. A knot of excess X-ray emission is coincident with the other bright elliptical galaxy F. This knot of emission has properties similar to the enhanced emission associated with the large galaxies in the Coma cluster. With these Chandra data we are able to compare the properties of the hot X-ray gas with those of the radio relic from VLA data, to study the interaction of the X-ray gas with the radio emitting electrons. Our results suggest that the radio re...

  20. ASA's Chandra Neon Discovery Solves Solar Paradox

    Science.gov (United States)

    2005-07-01

    NASA's Chandra X-ray Observatory survey of nearby sun-like stars suggests there is nearly three times more neon in the sun and local universe than previously believed. If true, this would solve a critical problem with understanding how the sun works. "We use the sun to test how well we understand stars and, to some extent, the rest of the universe," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "But in order to understand the sun, we need to know exactly what it is made of," he added. It is not well known how much neon the sun contains. This is critical information for creating theoretical models of the sun. Neon atoms, along with carbon, oxygen and nitrogen, play an important role in how quickly energy flows from nuclear reactions in the sun's core to its edge, where it then radiates into space. Chandra X-ray Spectrum of II Pegasi Chandra X-ray Spectrum of II Pegasi The rate of this energy flow determines the location and size of a crucial stellar region called the convection zone. The zone extends from near the sun's surface inward approximately 125,000 miles. The zone is where the gas undergoes a rolling, convective motion much like the unstable air in a thunderstorm. "This turbulent gas has an extremely important job, because nearly all of the energy emitted at the surface of the sun is transported there by convection," Drake said. The accepted amount of neon in the sun has led to a paradox. The predicted location and size of the solar convection zone disagree with those deduced from solar oscillations. Solar oscillations is a technique astronomers previously relied on to probe the sun's interior. Several scientists have noted the problem could be fixed if the abundance of neon is in fact about three times larger than currently accepted. Attempts to measure the precise amount of neon in the Sun have been frustrated by a quirk of nature; neon atoms in the Sun give off no signatures in visible light. However, in a gas

  1. High energy physics and cosmology

    International Nuclear Information System (INIS)

    This research will focus on the implications of recent theories and experiments in high energy physics of the evolution of the early universe, and on the constraints that cosmological considerations can place on such theories. Several problems are under investigation, including studies of the nature of dark matter and the signature of annihilations in the galactic halo, where the resulting γ-ray fluxes are potentially observable, and in stars, where stellar evolution may be affects. We will develop constraints on the inflationary predictions of scale-free primordial fluctuations in a universe at critical closure density by studying their linear and non-linear evolution after they re-enter the particle horizon, examining the observable imprint of primordial density fluctuations on the cosmic microwave background radiation in both flat and curved cosmological models, and implications for observations of large-scale galaxy clustering and structure formation theories. We will also study spectral distortions in the microwave background radiation that are produced by exotic particle decays in the very early universe. We expect such astrophysical considerations to provide fruitful insights both into high-energy particle physics and into possible cosmological for the early universe

  2. Inflation and cosmological parameter estimation

    Energy Technology Data Exchange (ETDEWEB)

    Hamann, J.

    2007-05-15

    In this work, we focus on two aspects of cosmological data analysis: inference of parameter values and the search for new effects in the inflationary sector. Constraints on cosmological parameters are commonly derived under the assumption of a minimal model. We point out that this procedure systematically underestimates errors and possibly biases estimates, due to overly restrictive assumptions. In a more conservative approach, we analyse cosmological data using a more general eleven-parameter model. We find that regions of the parameter space that were previously thought ruled out are still compatible with the data; the bounds on individual parameters are relaxed by up to a factor of two, compared to the results for the minimal six-parameter model. Moreover, we analyse a class of inflation models, in which the slow roll conditions are briefly violated, due to a step in the potential. We show that the presence of a step generically leads to an oscillating spectrum and perform a fit to CMB and galaxy clustering data. We do not find conclusive evidence for a step in the potential and derive strong bounds on quantities that parameterise the step. (orig.)

  3. Local Experiments See Cosmologically Varying Constants

    CERN Document Server

    Shaw, D J; Barrow, John D.; Shaw, Douglas J.

    2006-01-01

    We describe a rigorous construction, using matched asymptotic expansions, which establishes under very general conditions that local terrestrial and solar-system experiments will measure the effects of varying `constants' of Nature occurring on cosmological scales to computable precision. In particular, `constants' driven by scalar fields will still be found to evolve in time when observed within virialised structures like clusters, galaxies, and planetary systems. This provides a justification for combining cosmological and terrestrial constraints on the possible time variation of many assumed `constants' of Nature, including the fine structure constant and Newton's gravitation constant.

  4. Cosmological models and stability

    CERN Document Server

    Andersson, Lars

    2013-01-01

    Principles in the form of heuristic guidelines or generally accepted dogma play an important role in the development of physical theories. In particular, philosophical considerations and principles figure prominently in the work of Albert Einstein. As mentioned in the talk by Jiri Bicak at this conference Einstein formulated the equivalence principle, an essential step on the road to general relativity, during his time in Prague 1911-1912. In this talk, I would like to discuss some aspects of cosmological models. As cosmology is an area of physics where "principles" such as the "cosmological principle" or the "Copernican principle" play a prominent role in motivating the class of models which form part of the current standard model, I will start by comparing the role of the equivalence principle to that of the principles used in cosmology. I will then briefly describe the standard model of cosmology to give a perspective on some mathematical problems and conjectures on cosmological models, which are discussed...

  5. Swift J1644+57: Chandra observations

    Science.gov (United States)

    Levan, A. J.; Tanvir, N. R.

    2012-11-01

    We observed the X-ray counterpart to the candidate relativistic tidal disruption event Swift J1644+57 (Levan et al. 2011 Science, 333 199; Bloom et al. 2011 Science 333 202; Burrows et al. 2011 Nature 476 421; Zauderer et al. 2011 Nature 476 425) with the Chandra X-ray Observatory, beginning on 26 November 2012 at 10:25 UT. A total integration of 24.7 ks was obtained, and the object was placed at the default position on the ACIS S3 chip.

  6. An X-ray Tour of Massive Star-forming Regions with Chandra

    CERN Document Server

    Townsley, L K

    2006-01-01

    The Chandra X-ray Observatory is providing fascinating new views of massive star-forming regions, revealing all stages in the life cycles of massive stars and their effects on their surroundings. I present a Chandra tour of some of the most famous of these regions: M17, NGC 3576, W3, Tr14 in Carina, and 30 Doradus. Chandra highlights the physical processes that characterize the lives of these clusters, from the ionizing sources of ultracompact HII regions (W3) to superbubbles so large that they shape our views of galaxies (30 Dor). X-ray observations usually reveal hundreds of pre-main sequence (lower-mass) stars accompanying the OB stars that power these great HII region complexes, although in one case (W3 North) this population is mysteriously absent. The most massive stars themselves are often anomalously hard X-ray emitters; this may be a new indicator of close binarity. These complexes are sometimes suffused by soft diffuse X-rays (M17, NGC 3576), signatures of multi-million-degree plasmas created by fas...

  7. Cosmology and particle physics

    International Nuclear Information System (INIS)

    This paper comprises the contents of four lectures in which the author illustrates the two-way nature of the interplay between the fields of cosmology and particle physics by focusing on several specifics: a review of the standard cosmology, concentrating on primordial nucleosynthesis; baryogenesis; monopoles; and the case in which a very early first-order phase transition associated with spontaneous symmetry breaking has the potential to explain some very fundamental cosmological facts

  8. Neutrinos in cosmology

    OpenAIRE

    Dolgov, A.D.(Novosibirsk State University, Novosibirsk, 630090, Russia)

    2002-01-01

    Cosmological implications of neutrinos are reviewed. The following subjects are discussed at a different level of scrutiny: cosmological limits on neutrino mass, neutrinos and primordial nucleosynthesis, cosmological constraints on unstable neutrinos, lepton asymmetry of the universe, impact of neutrinos on cosmic microwave radiation, neutrinos and the large scale structure of the universe, neutrino oscillations in the early universe, baryo/lepto-genesis and neutrinos, neutrinos and high ener...

  9. Cosmology and time

    Directory of Open Access Journals (Sweden)

    Balbi Amedeo

    2013-09-01

    Full Text Available Time has always played a crucial role in cosmology. I review some of the aspects of the present cosmological model which are more directly related to time, such as: the definition of a cosmic time; the existence of typical timescales and epochs in an expanding universe; the problem of the initial singularity and the origin of time; the cosmological arrow of time.

  10. MOND and Cosmology

    OpenAIRE

    Sanders, R. H.

    2005-01-01

    I review various ideas on MOND cosmology and structure formation beginning with non-relativistic models in analogy with Newtonian cosmology. I discuss relativistic MOND cosmology in the context of Bekenstein's theory and propose an alternative biscalar effective theory of MOND in which the acceleration parameter is identified with the cosmic time derivative of a matter coupling scalar field. Cosmic CDM appears in this theory as scalar field oscillations of the auxiliary "coupling strength" fi...

  11. Sociology of Modern Cosmology

    CERN Document Server

    Lopez-Corredoira, Martin

    2008-01-01

    Certain results of observational cosmology cast critical doubt on the foundations of standard cosmology but leave most cosmologists untroubled. Alternative cosmological models that differ from the Big Bang have been published and defended by heterodox scientists; however, most cosmologists do not heed these. This may be because standard theory is correct and all other ideas and criticisms are incorrect, but it is also to a great extent due to sociological phenomena such as the "snowball effect" or "groupthink". We might wonder whether cosmology, the study of the Universe as a whole, is a science like other branches of physics or just a dominant ideology.

  12. Sociology of Modern Cosmology

    Science.gov (United States)

    López-Corredoira, M.

    2009-08-01

    Certain results of observational cosmology cast critical doubt on the foundations of standard cosmology but leave most cosmologists untroubled. Alternative cosmological models that differ from the Big Bang have been published and defended by heterodox scientists; however, most cosmologists do not heed these. This may be because standard theory is correct and all other ideas and criticisms are incorrect, but it is also to a great extent due to sociological phenomena such as the ``snowball effect'' or ``groupthink''. We might wonder whether cosmology, the study of the Universe as a whole, is a science like other branches of physics or just a dominant ideology.

  13. Grand unified models and cosmology

    OpenAIRE

    Jeannerot, Rachel

    2006-01-01

    The cosmological consequences of particle physics grand unified theories (GUTs) are studied. Cosmological models are implemented in realistic particle physics models. Models consistent from both particle physics and cosmological considerations are selected. (...)

  14. Chandra Observations of SNR RCW 103

    CERN Document Server

    Frank, Kari A; Park, Sangwook

    2015-01-01

    We analyze three Chandra observations, with a combined exposure time of 99 ks, of the Galactic supernova remnant RCW 103, a young supernova remnant, previously with no clear detection of metal-rich ejecta. Based on our imaging and spectral analyses of these deep Chandra data, we find evidence for metal-rich ejecta emission scattered throughout the remnant. X-ray emission from the shocked ejecta is generally weak, and the shocked circumstellar medium (CSM) is a largely dominant component across the entire remnant. The CSM component shows abundances of ~0.5 solar, while Ne, Mg, Si, S, and Fe abundances of the ejecta are up to a few times solar. Comparison of these ejecta abundances with yields from supernova nucleosynthesis models suggests, together with the existence of a central neutron star, a progenitor mass of ~18-20 M$_\\odot$, though the Fe/Si ratios are larger than predicted. The shocked CSM emission suggests a progenitor with high mass-loss rate and subsolar metallicity.

  15. Chandra mission scheduling on-orbit experience

    Science.gov (United States)

    Bucher, Sabina; Williams, Brent; Pendexter, Misty; Balke, David

    2008-07-01

    Scheduling observatory time to maximize both day-to-day science target integration time and the lifetime of the observatory is a formidable challenge. Furthermore, it is not a static problem. Of course, every schedule brings a new set of observations, but the boundaries of the problem change as well. As spacecraft ages, its capabilities may degrade. As in-flight experience grows, capabilities may expand. As observing programs are completed, the needs and expectations of the science community may evolve. Changes such as these impact the rules by which a mission scheduled. In eight years on orbit, the Chandra X-Ray Observatory Mission Planning process has adapted to meet the challenge of maximizing day-to-day and mission lifetime science return, despite a consistently evolving set of scheduling constraints. The success of the planning team has been achieved, not through the use of complex algorithms and optimization routines, but through processes and home grown tools that help individuals make smart short term and long term Mission Planning decisions. This paper walks through the processes and tools used to plan and produce mission schedules for the Chandra X-Ray Observatory. Nominal planning and scheduling, target of opportunity response, and recovery from on-board autonomous safing actions are all addressed. Evolution of tools and processes, best practices, and lessons learned are highlighted along the way.

  16. Stellar Forensics with Striking Image from Chandra

    Science.gov (United States)

    2007-10-01

    A spectacular new image shows how complex a star's afterlife can be. By studying the details of this image made from a long observation by NASA's Chandra X-ray Observatory, astronomers can better understand how some stars die and disperse elements like oxygen into the next generation of stars and planets. At a distance of about 20,000 light years, G292.0+1.8 is one of only three supernova remnants in the Milky Way known to contain large amounts of oxygen. The image shows a rapidly expanding, intricately structured, debris field that contains, along with oxygen, other elements such as neon and silicon that were forged in the star before it exploded. Hard X-ray Image of G292.0+1.8 Hard X-ray Image of G292.0+1.8 "We are finding that, just like snowflakes, each supernova remnant is complicated and beautiful in its own way," said Sangwook Park of Penn State who led the work, released in conjunction with the "8 Years of Chandra" symposium in Huntsville, Ala. The new, deep Chandra image - equaling nearly 6 days worth of observing time - shows an incredibly complex structure. Understanding the details of G292.0+1.8 is especially important because astronomers have considered it to be a "textbook" case of a supernova created by the death of a massive star. Chandra X-ray Image of G292.0+1.8 Chandra X-ray Image of G292.0+1.8 By mapping the distribution of X-rays in different energy bands, the Chandra image traces the distribution of chemical elements ejected in the supernova. The results imply that the explosion was not symmetrical. For example, blue (silicon and sulfur) and green (magnesium) are seen strongly in the upper right, while yellow and orange (oxygen) dominate the lower left. These elements light up at different temperatures, indicating that the temperature is higher in the upper right portion of G292.0+1.8. Slightly below and to the left of the center of G292.0+1.8 is a pulsar, a dense, rapidly rotating neutron star that remained behind after the original star

  17. Spectral Analysis of the Chandra Comet Survey

    CERN Document Server

    Bodewits, D; Torney, M; Dryer, M; Lisse, C M; Dennerl, K; Zurbuchen, T H; Wolk, S J; Tielens, A G G M; Hoekstra, R

    2007-01-01

    We present results of the analysis of cometary X-ray spectra with an extended version of our charge exchange emission model (Bodewits et al. 2006). We have applied this model to the sample of 8 comets thus far observed with the Chandra X-ray observatory and ACIS spectrometer in the 300-1000 eV range. The surveyed comets are C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), C/2000 WM1 (LINEAR), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), C/2001 Q4 (NEAT), 9P/2005 (Tempel 1) and 73P/2006-B (Schwassmann-Wachmann 3) and the observations include a broad variety of comets, solar wind environments and observational conditions. The interaction model is based on state selective, velocity dependent charge exchange cross sections and is used to explore how cometary X-ray emission depend on cometary, observational and solar wind characteristics. It is further demonstrated that cometary X-ray spectra mainly reflect the state of the local solar wind. The current sample of Chandra observations was fit using the constrains of ...

  18. Chandra X-ray observation of the HII region Gum 31 in the Carina Nebula complex

    CERN Document Server

    Preibisch, T; Townsley, L; Broos, P; Ratzka, T

    2014-01-01

    (abridged) We used the Chandra observatory to perform a deep (70 ksec) X-ray observation of the Gum 31 region and detected 679 X-ray point sources. This extends and complements the X-ray survey of the central Carina nebula regions performed in the Chandra Carina Complex Project. Using deep near-infrared images from our recent VISTA survey of the Carina nebula complex, our Spitzer point-source catalog, and optical archive data, we identify counterparts for 75% of these X-ray sources. Their spatial distribution shows two major concentrations, the central cluster NGC 3324 and a partly embedded cluster in the southern rim of the HII region, but majority of X-ray sources constitute a rather homogeneously distributed population of young stars. Our color-magnitude diagram analysis suggests ages of ~1-2 Myr for the two clusters, whereas the distributed population shows a wider age range up to ~10 Myr. We also identify previously unknown companions to two of the three O-type members of NGC 3324 and detect diffuse X-ra...

  19. HDE 245059: A Weak-Lined T Tauri Binary Revealed by Chandra and Keck

    OpenAIRE

    Saavedra, C. Baldovin; Audard, M.; Duchêne, G.; Güdel, M.; Skinner, S.L.; Paerels, F. B. S.; Ghez, A.; McCabe, C.

    2009-01-01

    We present the Chandra High Energy Transmission Grating Spectrometer (HETGS) and Keck observations of HDE 245059, a young weak-lined T Tauri star (WTTS), member of the pre-main sequence group in the Lambda Orionis Cluster. Our high spatial resolution, near-infrared observations with Keck reveal that HDE 245059 a binary separated by 0.87". Based on this new information we have obtained an estimate of the masses of the binary components; 3M_{sun} and 2.5M_{sun} for the north and south component...

  20. The relation between mass and concentration in X-ray galaxy clusters at high redshift

    CERN Document Server

    Amodeo, Stefania; Capasso, Raffaella; Sereno, Mauro

    2016-01-01

    Galaxy clusters are the most recent, gravitationally-bound products of the hierarchical mass accretion over cosmological scales. How the mass is concentrated is predicted to correlate with the total mass in the cluster's halo, with systems at higher mass being less concentrated at given redshift and for any given mass, systems with lower concentration are found at higher redshifts. Through a spatial and spectral X-ray analysis, we reconstruct the total mass profile of 47 galaxy clusters observed with Chandra in the redshift range $0.40.4$, and is well suited to provide the first constraint on the concentration--mass relation at $z>0.7$ from X-ray analysis. Under the assumptions that the distribution of the X-ray emitting gas is spherically symmetric and in hydrostatic equilibrium, we combine the deprojected gas density and spectral temperature profiles through the hydrostatic equilibrium equation to recover the parameters that describe a NFW total mass distribution. The comparison with results from weak lensi...

  1. The speed of the `bullet' in the merging galaxy cluster 1E0657-56

    CERN Document Server

    Springel, V; Springel, Volker; Farrar, Glennys

    2007-01-01

    Deep Chandra exposures of the hot galaxy cluster 1E0657-56 have revealed that the cluster is observed shortly after the first core-passage of a massive infalling subcluster, which is preceded by a prominent bow shock with Mach number M~3. The inferred shock velocity of ~4700 km/s has been commonly interpreted as the velocity of the `bullet' subcluster itself. This velocity is unexpectedly high in the LCDM cosmology, which may require non-trivial modifications in the dark sector to be accommodated if taken at face value. Here we present explicit hydrodynamical toy models of galaxy cluster mergers which very well reproduce the observed dynamical state of 1E0657-56 and the mass models inferred from gravitational lensing observations. However, despite a shock speed of 4500 km/s, the subcluster's mass centroid is moving only with 2600 km/s in the rest frame of the system. The difference arises in part due to a gravitationally induced inflow velocity of the gas ahead of the shock, which amounts to ~1100 km/s for ou...

  2. Astroparticle physics and cosmology

    International Nuclear Information System (INIS)

    In this volume a wide spectrum of topics of modern astroparticle physics, such as neutrino astrophysics, dark matter of the universe, high energy cosmic rays, topological defects in cosmology, γ-ray bursts, phase transitions at high temperatures, is covered. The articles written by top level experts in the field give a comprehensive view of the state-of-the-art of modern cosmology

  3. Dwarf-Galaxy Cosmology

    CERN Document Server

    Schulte-Ladbeck, Regina; Brinks, Elias; Kravtsov, Andrey

    2010-01-01

    Dwarf galaxies provide opportunities for drawing inferences about the processes in the early universe by observing our "cosmological backyard"-the Local Group and its vicinity. This special issue of the open-access journal Advances in Astronomy is a snapshot of the current state of the art of dwarf-galaxy cosmology.

  4. How To Cover NASA's Chandra X-ray Observatory

    Science.gov (United States)

    1999-07-01

    NASA's newest space telescope, the Chandra X-ray Observatory, is scheduled for launch not earlier than July 20, 1999, aboard Space Shuttle mission STS-93. The world's most powerful X-ray observatory, Chandra will join the Hubble Space Telescope and NASA's other great observatories in an unprecedented study of our universe. With its capability to "see" an otherwise invisible but violent, vibrant and ever-changing universe, Chandra will provide insights into the universe's structure and evolution. The following information is designed to assist news media representatives cover launch and activation of the Chandra X-ray Observatory. Covering from the Chandra Control Center NASA will establish a news center at the Chandra X-ray Observatory Operations Control Center in Cambridge, Mass., during the critical period of launch and early activation. The news center will be open from approximately two days prior to launch until the observatory is established in its operating orbit approximately 11 days after launch. The telephone numbers for the news center are: (617) 496-4454 (617) 496-4462 (617) 496-4484 The news center will be staffed around the clock during the Shuttle mission by media relations officers knowledgeable about the Chandra mission and its status. Media covering from the news center will be provided work space and have opportunities for face-to-face interviews with Chandra management, control team members and Chandra scientists. They will be able to participate in daily Chandra status briefings and have access to a special control room viewing area. Additionally, media covering from Cambridge will receive periodic status reports on Chandra and the STS-93 mission, and will be able to participate in interactive televised briefings on the STS-93 mission originating from other NASA centers. While advance accreditation is not required, media interested in covering Chandra from the Operations Control Center should contact Dave Drachlis by telephone at (256) 544

  5. The velocity field in MOND cosmology

    Science.gov (United States)

    Candlish, G. N.

    2016-08-01

    The recently developed code for N-body/hydrodynamics simulations in Modified Newtonian Dynamics (MOND), known as RAYMOND, is used to investigate the consequences of MOND on structure formation in a cosmological context, with a particular focus on the velocity field. This preliminary study investigates the results obtained with the two formulations of MOND implemented in RAYMOND, as well as considering the effects of changing the choice of MOND interpolation function, and the cosmological evolution of the MOND acceleration scale. The simulations are contrived such that structure forms in a background cosmology that is similar to Λcold dark matter, but with a significantly lower matter content. Given this, and the fact that a fully consistent MOND cosmology is still lacking, we compare our results with a standard ΛCDM simulation, rather than observations. As well as demonstrating the effectiveness of using RAYMOND for cosmological simulations, it is shown that a significant enhancement of the velocity field is likely an unavoidable consequence of the gravitational modification implemented in MOND, and may represent a clear observational signature of such a modification. It is further suggested that such a signal may be clearest in intermediate-density regions such as cluster outskirts and filaments.

  6. Cosmological measurements with general relativistic galaxy correlations

    Science.gov (United States)

    Raccanelli, Alvise; Montanari, Francesco; Bertacca, Daniele; Doré, Olivier; Durrer, Ruth

    2016-05-01

    We investigate the cosmological dependence and the constraining power of large-scale galaxy correlations, including all redshift-distortions, wide-angle, lensing and gravitational potential effects on linear scales. We analyze the cosmological information present in the lensing convergence and in the gravitational potential terms describing the so-called ``relativistic effects'', and we find that, while smaller than the information contained in intrinsic galaxy clustering, it is not negligible. We investigate how neglecting them does bias cosmological measurements performed by future spectroscopic and photometric large-scale surveys such as SKA and Euclid. We perform a Fisher analysis using the CLASS code, modified to include scale-dependent galaxy bias and redshift-dependent magnification and evolution bias. Our results show that neglecting relativistic terms, especially lensing convergence, introduces an error in the forecasted precision in measuring cosmological parameters of the order of a few tens of percent, in particular when measuring the matter content of the Universe and primordial non-Gaussianity parameters. The analysis suggests a possible substantial systematic error in cosmological parameter constraints. Therefore, we argue that radial correlations and integrated relativistic terms need to be taken into account when forecasting the constraining power of future large-scale number counts of galaxy surveys.

  7. Chandra Captures Flare From Brown Dwarf

    Science.gov (United States)

    2000-07-01

    The first flare ever seen from a brown dwarf, or failed star, was detected by NASA's Chandra X-ray Observatory. The bright X-ray flare has implications for understanding the explosive activity and origin of magnetic fields of extremely low mass stars. Chandra detected no X-rays at all from LP 944-20 for the first nine hours of a twelve hour observation, then the source flared dramatically before it faded away over the next two hours. "We were shocked," said Dr. Robert Rutledge of the California Institute of Technology in Pasadena, the lead author on the discovery paper to appear in the July 20 issue of Astrophysical Journal Letters. "We didn't expect to see flaring from such a lightweight object. This is really the 'mouse that roared.'" Chandra LP 944-20 X-ray Image Press Image and Caption The energy emitted in the brown dwarf flare was comparable to a small solar flare, and was a billion times greater than observed X-ray flares from Jupiter. The flaring energy is believed to come from a twisted magnetic field. "This is the strongest evidence yet that brown dwarfs and possibly young giant planets have magnetic fields, and that a large amount of energy can be released in a flare," said Dr. Eduardo Martin, also of Caltech and a member of the team. Professor Gibor Basri of the University of California, Berkeley, the principal investigator for this observation, speculated that the flare "could have its origin in the turbulent magnetized hot material beneath the surface of the brown dwarf. A sub-surface flare could heat the atmosphere, allowing currents to flow and give rise to the X-ray flare -- like a stroke of lightning." LP 944-20 is about 500 million years old and has a mass that is about 60 times that of Jupiter, or 6 percent that of the Sun. Its diameter is about one-tenth that of the Sun and it has a rotation period of less than five hours. Located in the constellation Fornax in the southern skies, LP 944-20 is one of the best studied brown dwarfs because it is

  8. BMS in Cosmology

    CERN Document Server

    Kehagias, Alex

    2016-01-01

    Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to both scalar and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic d...

  9. Cosmology and particle physics

    Science.gov (United States)

    Turner, Michael S.

    1988-01-01

    The interplay between cosmology and elementary particle physics is discussed. The standard cosmology is reviewed, concentrating on primordial nucleosynthesis and discussing how the standard cosmology has been used to place constraints on the properties of various particles. Baryogenesis is discussed, showing how a scenario in which the B-, C-, and CP-violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and for the present baryon-to-photon ratio. It is shown how the very early dynamical evolution of a very weakly coupled scalar field which is initially displaced from the minimum of its potential may explain a handful of very fundamental cosmological facts which are not explained by the standard cosmology.

  10. Introduction to cosmology

    CERN Document Server

    Ryden, Barbara

    2002-01-01

    Introduction to Cosmology provides a rare combination of a solid foundation of the core physical concepts of cosmology and the most recent astronomical observations. The book is designed for advanced undergraduates or beginning graduate students and assumes no prior knowledge of general relativity. An emphasis is placed on developing the readers' physical insight rather than losing them with complex math. An approachable writing style and wealth of fresh and imaginative analogies from "everyday" physics are used to make the concepts of cosmology more accessible. The book is unique in that it not only includes recent major developments in cosmology, like the cosmological constant and accelerating universe, but also anticipates key developments expected in the next few years, such as detailed results on the cosmic microwave background.

  11. A Taste of Cosmology

    CERN Document Server

    Verde, L

    2013-01-01

    This is the summary of two lectures that aim to give an overview of cosmology. I will not try to be too rigorous in derivations, nor to give a full historical overview. The idea is to provide a "taste" of cosmology and some of the interesting topics it covers. The standard cosmological model is presented and I highlight the successes of cosmology over the past decade or so. Keys to the development of the standard cosmological model are observations of the cosmic microwave background and of large-scale structure, which are introduced. Inflation and dark energy and the outlook for the future are also discussed. Slides from the lectures are available from the school website: physicschool.web.cern.ch/PhysicSchool/CLASHEP/CLASHEP2011/.

  12. Preferred axis in cosmology

    CERN Document Server

    Zhao, Wen

    2016-01-01

    The foundation of modern cosmology relies on the so-called cosmological principle which states an homogeneous and isotropic distribution of matter in the universe on large scales. However, recent observations, such as the temperature anisotropy of the cosmic microwave background (CMB) radiation, the motion of galaxies in the universe, the polarization of quasars and the acceleration of the cosmic expansion, indicate preferred directions in the sky. If these directions have a cosmological origin, the cosmological principle would be violated, and modern cosmology should be reconsidered. In this paper, by considering the preferred axis in the CMB parity violation, we find that it coincides with the preferred axes in CMB quadrupole and CMB octopole, and they all align with the direction of the CMB kinematic dipole. In addition, the preferred directions in the velocity flows, quasar alignment, anisotropy of the cosmic acceleration, the handedness of spiral galaxies, and the angular distribution of the fine-structu...

  13. Ram Pressure Stripping of Hot Coronal Gas from Group and Cluster Galaxies and the Detectability of Surviving X-ray Coronae

    CERN Document Server

    Vijayaraghavan, Rukmani

    2015-01-01

    Ram pressure stripping can remove hot and cold gas from galaxies in the intracluster medium (ICM), as shown by observations of X-ray and HI galaxy wakes in nearby clusters of galaxies. However, ram pressure stripping, including pre-processing in group environments, does not remove all the hot coronal gas from cluster galaxies. Recent high-resolution Chandra observations have shown that $\\sim 1 - 4$ kpc extended, hot galactic coronae are ubiquitous in group and cluster galaxies. To better understand this result, we simulate ram pressure stripping of a cosmologically motivated population of galaxies in isolated group and cluster environments. The galaxies and the host group and cluster are composed of collisionless dark matter and hot gas initially in hydrostatic equilibrium with the galaxy and host potentials. We show that the rate at which gas is lost depends on the galactic and host halo mass. Using synthetic X-ray observations, we evaluate the detectability of stripped galactic coronae in real observations ...

  14. Testing cosmological models with the Integrated Sachs-Wolfe effect

    Energy Technology Data Exchange (ETDEWEB)

    Raccanelli, Alvise, E-mail: alvise.raccanelli@port.ac.uk [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom)

    2011-02-01

    The cross correlation between the Cosmic Microwave Background and the Large Scale Structure of the Universe is a powerful probe to test our cosmological models. This correlation can be used to detect the Integrated Sachs-Wolfe effect, and it depends on both the geometry of the Universe and the properties of the clustering and evolution of structures; for this reason it can be used to test and constrain cosmological models and parameters as well as theories of gravity. In this proceeding we briefly introduce the ISW effect and present some of the recent cosmological tests done using it.

  15. Galaxy Bias in Quintessence Cosmological Models

    CERN Document Server

    Basilakos, S

    2003-01-01

    We derive the evolution of the linear bias factor, $b(z)$, in cosmological models driven by an exotic fluid with an equation of state: $p_{x}=w\\rho_{x}$, where $-1\\le w<0$ (quintessence). Our aim is to put constrains on different cosmological and biasing models by combining the recent observational clustering results of optical ({\\em 2dF}) galaxies (Hawkings et al.) with those predicted by the models. We find that our bias model when fitted to the {\\em 2dF} clustering results predicts different bias evolution for different values of $w$. The models that provide the weak biasing ($b_{\\circ} \\sim 1.1$) of optical galaxies found in many recent observational studies are flat, $\\Omega_{\\rm m}=0.3$ with $w\\le -0.9$. These models however, predict a weak redshift evolution of $b(z)$, not corroborated by N-body simulations.

  16. Chandra data archive operations: lessons learned

    Science.gov (United States)

    McCollough, Michael L.; Rots, Arnold H.; Winkelman, Sherry L.

    2006-06-01

    We present a discussion of the lessons learned from establishing and operating the Chandra Data Archive (CDA). We offer an overview of the archive, what preparations were done before launch, the transition to operations, actual operations, and some of the unexpected developments that had to be addressed in running the archive. From this experience we highlight some of the important issues that need to be addressed in the creation and running of an archive for a major project. Among these are the importance of data format standards; the integration of the archive with the rest of the mission; requirements throughout all phases of the mission; operational requirements; what to expect at launch; the user interfaces; how to anticipate new tasks; and overall importance of team management and organization.

  17. The BMW-Chandra Serendipitous Source Catalogue

    Science.gov (United States)

    Romano, P.; Campana, S.; Mignani, R. P.; Moretti, A.; Panzera, M. R.; Tagliaferri, G.

    We present the BMW-Chandra Source Catalogue drawn from all Chandra ACIS-I pointed observations with an exposure time in excess of 10 ks public as of March 2003 (136 observations). Using the wavelet detection algorithm developed by \\citep{Lazzatiea99} and \\citep{Campanaea99}, which can characterize point-like as well as extended sources, we identified 21325 sources which were visually inspected and verified. Among them, 16758 are not associated with the targets of the pointings and are considered certain; they have a 0.5-10 keV absorption corrected flux distribution median of ˜ 7 × 10-15 erg cm-2 s-1. The catalogue consists of source positions, count rates, extensions and relative errors in three energy bands (total, 0.5-7 keV; soft, 0.5-2 keV; and hard band, 2-7 keV), as well as the additional information drawn from the headers of the original files. We also extracted source counts in four additional energy bands, (0.5-1.0 keV, 1.0-2.0 keV, 2.0-4.0 keV and 4.0-7.0 keV). We compute the sky coverage in the soft and hard bands. The complete catalogue provides a sky coverage in the soft band (0.5-2 keV, S/N =3) of ˜ 8 deg2 at a limiting flux of ˜ 10-13 erg cm-2 s-1, and ˜ 2 deg2 at a limiting flux of ˜ 10-15 erg cm-2 s-1. http://www.merate.mi.astro.it/~xanadu/BMC/bmc_home.html

  18. Gravitational Renormalization Group Flow, Astrophysics and Cosmology

    CERN Document Server

    Moffat, J W

    2015-01-01

    A modified gravitational theory is developed in which the gravitational coupling constants $G$ and $Q$ and the effective mass $m_\\phi$ of a repulsive vector field run with momentum scale $k$ or length scale $\\ell =1/k$, according to a renormalization group flow. The theory can explain cosmological early universe data with a dark hidden photon and late time galaxy and cluster dynamics without dark matter. The theory agrees with solar system and binary pulsar observations.

  19. Using supercluster geometry as a cosmological probe

    CERN Document Server

    Basilakos, S; Plionis, M

    2001-01-01

    We study the properties of superclusters detected in the Abell/ACO cluster catalogue. We identify the superclusters utilizing the `friend-of-friend' procedure, and then determine supercluster shapes by using the differential geometry approach. We find that the dominant supercluster morphological feature is filamentariness. We compare our Abell/ACO supercluster results with the corresponding ones generated from two different CDM cosmological models in order to investigate statistically which of the latter models best reproduces the observational results.

  20. BMS in cosmology

    Science.gov (United States)

    Kehagias, A.; Riotto, A.

    2016-05-01

    Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to scalar, vector and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic data. Therefore, BMS transformations generate physically inequivalent vacua as they populate the universe at null infinity with these physical degrees of freedom. We also discuss the gravitational memory effect when cosmological expansion is taken into account. In this case, there are extra contribution to the gravitational memory due to the tail of the retarded Green functions which are supported not only on the light-cone, but also in its interior. The gravitational memory effect can be understood also from an asymptotic point of view as a transition among cosmological BMS-related vacua.

  1. Unimodular-mimetic cosmology

    Science.gov (United States)

    Nojiri, S.; Odintsov, S. D.; Oikonomou, V. K.

    2016-06-01

    We combine the unimodular gravity and mimetic gravity theories into a unified theoretical framework, which is proposed to provide a suggestive proposal for a framework that may assist in the discussion and search for a solution to the cosmological constant problem and the dark matter issue. After providing the formulation of the unimodular mimetic gravity and investigating all the new features that the vacuum unimodular gravity implies, by using the underlying reconstruction method, we realize some well known cosmological evolutions, with some of these being exotic for the ordinary Einstein-Hilbert gravity. Specifically we provide the vacuum unimodular mimetic gravity description of the de Sitter cosmology and of the perfect fluid with constant equation of state cosmology. As we demonstrate, these cosmologies can be realized by vacuum mimetic unimodular gravity, without the existence of any matter fluid source. Moreover, we investigate how cosmologically viable cosmologies, which are compatible with the recent observational data, can be realized by the vacuum unimodular mimetic gravity. Since in some cases, a graceful exit from inflation problem might exist, we provide a qualitative description of the mechanism that can potentially generate the graceful exit from inflation in these theories, by searching for the unstable de Sitter solutions in the context of unimodular mimetic theories of gravity.

  2. Magnetogenesis in bouncing cosmology

    CERN Document Server

    Qian, Peng; Easson, Damien A; Guo, Zong-Kuan

    2016-01-01

    We consider the process of magnetogenesis in the context of nonsingular bounce cosmology. We show that large primordial magnetic fields can be generated during contraction without encountering strong coupling and backreaction issues. The fields may seed large-scale magnetic fields with observationally interesting strengths. This result leads to a theoretical constraint on the relation of the energy scale of the bounce cosmology to the number of effective e-folding of the contracting phase in the case of scale invariance for the power spectrum of primordial magnetic fields. We show that this constraint can be satisfied in a sizable region of the parameter space for the nonsingular bounce cosmology.

  3. Neutrino properties from cosmology

    DEFF Research Database (Denmark)

    Hannestad, S.

    2013-01-01

    In recent years precision cosmology has become an increasingly powerful probe of particle physics. Perhaps the prime example of this is the very stringent cosmological upper bound on the neutrino mass. However, other aspects of neutrino physics, such as their decoupling history and possible non......-standard interactions, can also be probed using observations of cosmic structure. Here, I review the current status of cosmological bounds on neutrino properties and discuss the potential of future observations, for example by the recently approved EUCLID mission, to precisely measure neutrino properties....

  4. Consistency of Hitomi, XMM-Newton and Chandra 3.5 keV data from Perseus

    OpenAIRE

    Conlon, Joseph P; Day, Francesca; Jennings , Nicholas; Krippendorf, Sven; Rummel, Markus

    2016-01-01

    Hitomi observations of Perseus with the Soft X-ray Spectrometer (SXS) provide a high-resolution look at the 3.5 keV feature reported by multiple groups in the Perseus cluster. The Hitomi spectrum -- which involves the sum of diffuse cluster emission and the point-like central Active Galactic Nucleus (AGN) -- does not show any excess at $E \\sim 3.5 {\\rm keV}$, giving an apparent inconsistency with previous observations of excess diffuse emission. We point out that 2009 Chandra data reveals a s...

  5. Weak Gravitational Lensing and its Cosmological Applications

    CERN Document Server

    Hoekstra, Henk

    2008-01-01

    Weak gravitational lensing is a unique probe of the dark side of the universe: it provides a direct way to map the distribution of dark matter around galaxies, clusters of galaxies and on cosmological scales. Furthermore, the measurement of lensing induced distortions of the shapes of distant galaxies is a powerful probe of dark energy. In this review we describe how lensing measurements are made and interpreted. We discuss various systematic effects that can hamper progress and how they may be overcome. We review some of the recent results in weak lensing by galaxies, galaxy clusters and cosmic shear and discuss the prospects for dark energy measurements from planned surveys.

  6. Do Relaxed Clusters of Galaxies Exist?

    Science.gov (United States)

    Motl, Patrick M.; Burns, Jack O.; Norman, Michael L.

    2004-05-01

    Clusters of galaxies lacking observational signatures of mergers and other complications are popular targets as cosmological probes. However, the assumptions of structural simplicity must be approximations that are valid to only a certain level. Especially in the new era of precision cosmology where efforts are underway to investigate the nature and evolution of dark energy, it is crucial to calibrate the approximations used to reduce cluster observations to cosmological measurements. We use high-resolution simulations of clusters of galaxies, evolved within their cosmological environment, to study the process of reducing X-ray and/or Sunyaev-Zeldovich data to cluster observables such as the gravitating mass and Hubble constant. This allows us to measure the impact of structure formation on these observables and quantify the approximations used in interpreting cluster observations.

  7. Six Years of Chandra Observations of Supernova Remnants

    OpenAIRE

    Weisskopf, Martin C.; Hughes, John P.

    2005-01-01

    We present a review of the first six years of Chandra X-ray Observatory observations of supernova remnants. From the official "first-light" observation of Cassiopeia A that revealed for the first time the compact remnant of the explosion, to the recent million-second spectrally-resolved observation that revealed new details of the stellar composition and dynamics of the original explosion, Chandra observations have provided new insights into the supernova phenomenon. We present an admittedly ...

  8. Virial mass in DGP cosmology

    CERN Document Server

    Shahidi, Shahab

    2012-01-01

    In this proposal we study the problem of the virial mass discrepancy in the context of DGP brane gravity. DGP model is a kind of brane-world model such that the corrections to the usual gravity occurred in the large distance limit relative to the distance scale of the model defined as a ratio of the brane Planck scale to the bulk Planck scale. The extra dimension of this model is noncompact. This model is composed with an Einstein-Hilbert action in 5 dimensions plus an induced 4D action guarantees the existence of gravity on the brane. The importance of this model is that it can explain the self-acceleration of our universe without use of any type of dark energy. The virial mass discrepancy is an important problem in cosmology and it can be explained by dark matter. This is due to our various ways in measurement of the mass of the galaxy clusters. One of the ways we can measure the mass of a cluster of galaxies is to measure the galaxy masses and then add them up to obtain the cluster mass. Another way is to ...

  9. Inhomogeneous Anisotropic Cosmology

    CERN Document Server

    Kleban, Matthew

    2016-01-01

    In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that ${\\it arbitrarily}$ inhomogeneous and anisotropic cosmologies with "flat" (including toroidal) and "open" (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potenti...

  10. Baryogenesis and cosmological antimatter

    CERN Document Server

    Dolgov, A D

    2009-01-01

    Possible mechanisms of baryogenesis are reviewed. Special attention is payed to those which allow for creation of astronomically significant domains or objects consisting of antimatter. Observational manifestations of cosmological antimatter are discussed.

  11. Erice lectures on cosmology

    International Nuclear Information System (INIS)

    This chapter presents lectures on big-bang cosmology; contents of the universe (especially neutrinos); matterantimatter asymmetry; and mysteries in the sky. Discusses dynamic equations of cosmology; the relation to Hubble parameters; simple solutions; the global structure of the universe (fixed cosmic time); global structure (dynamics); red-shift; observational handles on closure questions; notable events in universal history; neutrino decoupling; density of the neutrino gas; the mass limit on cosmologically stable neutrinos; nucleosynthesis; neutrino stability; neutrino mass and galaxy formation; evidence for asymmetry; requirements for a theory of asymmetry; a simple scenario (drift and decay); microscopics; thermalization; horizons; background radiation; a large entropy; monopoles; and a cosmological constant. Presents discussions featuring D'Hoker, Wilczek, Teller and others

  12. Cosmological Probes for Supersymmetry

    Directory of Open Access Journals (Sweden)

    Maxim Khlopov

    2015-05-01

    Full Text Available The multi-parameter character of supersymmetric dark-matter models implies the combination of their experimental studies with astrophysical and cosmological probes. The physics of the early Universe provides nontrivial effects of non-equilibrium particles and primordial cosmological structures. Primordial black holes (PBHs are a profound signature of such structures that may arise as a cosmological consequence of supersymmetric (SUSY models. SUSY-based mechanisms of baryosynthesis can lead to the possibility of antimatter domains in a baryon asymmetric Universe. In the context of cosmoparticle physics, which studies the fundamental relationship of the micro- and macro-worlds, the development of SUSY illustrates the main principles of this approach, as the physical basis of the modern cosmology provides cross-disciplinary tests in physical and astronomical studies.

  13. Cosmology Beyond Einstein

    CERN Document Server

    Solomon, Adam R

    2015-01-01

    The accelerating expansion of the Universe poses a major challenge to our understanding of fundamental physics. One promising avenue is to modify general relativity and obtain a new description of the gravitational force. Because gravitation dominates the other forces mostly on large scales, cosmological probes provide an ideal testing ground for theories of gravity. In this thesis, we describe two complementary approaches to the problem of testing gravity using cosmology. In the first part, we discuss the cosmological solutions of massive gravity and its generalisation to a bimetric theory. These theories describe a graviton with a small mass, and can potentially explain the late-time acceleration in a technically-natural way. We describe these self-accelerating solutions and investigate the cosmological perturbations in depth, beginning with an investigation of their linear stability, followed by the construction of a method for solving these perturbations in the quasistatic limit. This allows the predictio...

  14. Building Cosmological Frozen Stars

    CERN Document Server

    Kastor, David

    2016-01-01

    Janis-Newman-Winicour (JNW) spacetimes generalize the Schwarzschild solution to include a massless scalar field. Although suffering from naked singularities, they share the `frozen star' features of Schwarzschild black holes. Cosmological versions of the JNW spacetimes were discovered some time ago by Husain, Martinez and Nunez and by Fonarev. Unlike Schwarzschild-deSitter black holes, these solutions are dynamical, and the scarcity of exact solutions for dynamical black holes in cosmological backgrounds motivates their further study. Here we show how the cosmological JNW spacetimes can be built, starting from simpler, static, higher dimensional, vacuum `JNW brane' solutions via two different generalized dimensional reduction schemes that together cover the full range of JNW parameter space. Cosmological versions of a BPS limit of charged dilaton black holes are also known. JNW spacetimes represent a different limiting case of the charged, dilaton black hole family. We expect that understanding this second da...

  15. Cosmological Ontology and Epistemology

    CERN Document Server

    Page, Don N

    2014-01-01

    In cosmology, we would like to explain our observations and predict future observations from theories of the entire universe. Such cosmological theories make ontological assumptions of what entities exist and what their properties and relationships are. One must also make epistemological assumptions or metatheories of how one can test cosmological theories. Here I shall propose a Bayesian analysis in which the likelihood of a complete theory is given by the normalized measure it assigns to the observation used to test the theory. In this context, a discussion is given of the trade-off between prior probabilities and likelihoods, of the measure problem of cosmology, of the death of Born's rule, of the Boltzmann brain problem, of whether there is a better principle for prior probabilities than mathematical simplicity, and of an Optimal Argument for the Existence of God.

  16. Testing Fractional Action Cosmology

    CERN Document Server

    Shchigolev, V K

    2015-01-01

    The present work deals with a combined test of the so-called Fractional Action Cosmology (FAC) on the example of a specific model obtained by the author earlier. In this model, the effective cosmological term is proportional to the Hubble parameter squared through the so-called kinematic induction. The reason of studying this cosmological model could be explained by its ability to describe two periods of accelerated expansion, that is in agreement with the recent observations and the cosmological inflation paradigm. First of all, we put our model through the theoretical tests that gives a general conception of the influence of the model parameters on its behavior. Then, we obtain some restrictions on the principal parameters of the model, including the fractional index, by means of the observational data. Finally, the cosmography parameters and the observational data compared to the theoretical predictions are presented both analytically and graphically.

  17. Cosmology: macro and micro

    CERN Document Server

    Holland, Jonathan

    2014-01-01

    A new approach to cosmology and space-time is developed, which emphasizes the description of the matter degrees of freedom of Einstein's theory of gravity by a family of K\\"ahler-Einstein Fano manifolds.

  18. Cosmological Probes for Supersymmetry

    CERN Document Server

    Khlopov, Maxim

    2015-01-01

    The multi-parameter character of supersymmetric dark-matter models implies the combination of their experimental studies with astrophysical and cosmological probes. The physics of the early Universe provides nontrivial effects of non-equilibrium particles and primordial cosmological structures. Primordial black holes (PBHs) are a profound signature of such structures that may arise as a cosmological consequence of supersymmetric (SUSY) models. SUSY-based mechanisms of baryosynthesis can lead to the possibility of antimatter domains in a baryon asymmetric Universe. In the context of cosmoparticle physics, which studies the fundamental relationship of the micro- and macro-worlds, the development of SUSY illustrates the main principles of this approach, as the physical basis of the modern cosmology provides cross-disciplinary tests in physical and astronomical studies.

  19. Cosmology as geodesic motion

    Energy Technology Data Exchange (ETDEWEB)

    Townsend, Paul K [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Wohlfarth, Mattias N R [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

    2004-12-07

    For gravity coupled to N scalar fields, with arbitrary potential V, it is shown that all flat (homogeneous and isotropic) cosmologies correspond to geodesics in an (N + 1)-dimensional 'augmented' target space of Lorentzian signature (1, N), timelike if V > 0, null if V = 0 and spacelike if V < 0. Accelerating cosmologies correspond to timelike geodesics that lie within an 'acceleration subcone' of the 'lightcone'. Non-flat (k = {+-}1) cosmologies are shown to evolve as projections of geodesic motion in a space of dimension N + 2, of signature (1, N + 1) for k = -1 and signature (2, N) for k = +1. This formalism is illustrated by cosmological solutions of models with an exponential potential, which are comprehensively analysed; the late-time behaviour for other potentials of current interest is deduced by comparison.

  20. Testing fractional action cosmology

    Science.gov (United States)

    Shchigolev, V. K.

    2016-08-01

    The present work deals with a combined test of the so-called Fractional Action Cosmology (FAC) on the example of a specific model obtained by the author earlier. In this model, the effective cosmological term is proportional to the Hubble parameter squared through the so-called kinematic induction. The reason of studying this cosmological model could be explained by its ability to describe two periods of accelerated expansion, that is in agreement with the recent observations and the cosmological inflation paradigm. First of all, we put our model through the theoretical tests, which gives a general conception of the influence of the model parameters on its behavior. Then, we obtain some restrictions on the principal parameters of the model, including the fractional index, by means of the observational data. Finally, the cosmography parameters and the observational data compared to the theoretical predictions are presented both analytically and graphically.

  1. Tensors, relativity, and cosmology

    CERN Document Server

    Dalarsson, Mirjana

    2015-01-01

    Tensors, Relativity, and Cosmology, Second Edition, combines relativity, astrophysics, and cosmology in a single volume, providing a simplified introduction to each subject that is followed by detailed mathematical derivations. The book includes a section on general relativity that gives the case for a curved space-time, presents the mathematical background (tensor calculus, Riemannian geometry), discusses the Einstein equation and its solutions (including black holes and Penrose processes), and considers the energy-momentum tensor for various solutions. In addition, a section on relativistic astrophysics discusses stellar contraction and collapse, neutron stars and their equations of state, black holes, and accretion onto collapsed objects, with a final section on cosmology discussing cosmological models, observational tests, and scenarios for the early universe. This fully revised and updated second edition includes new material on relativistic effects, such as the behavior of clocks and measuring rods in m...

  2. Cosmological acceleration. Dark energy or modified gravity?

    Energy Technology Data Exchange (ETDEWEB)

    Bludman, S.

    2006-05-15

    We review the evidence for recently accelerating cosmological expansion or ''dark energy'', either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any constituent Dark Energy. If constituent Dark Energy does not exist, so that our universe is now dominated by pressure-free matter, Einstein gravity must be modified at low curvature. The vacuum symmetry of any Robertson-Walker universe then characterizes Dark Gravity as low- or high-curvature modifications of Einstein gravity. The dynamics of either kind of ''dark energy'' cannot be derived from the homogeneous expansion history alone, but requires also observing the growth of inhomogeneities. Present and projected observations are all consistent with a small fine tuned cosmological constant, but also allow nearly static Dark Energy or gravity modified at cosmological scales. The growth of cosmological fluctuations will potentially distinguish between static and ''dynamic'' ''dark energy''. But, cosmologically distinguishing the Concordance Model {lambda}CDM from modified gravity will require a weak lensing shear survey more ambitious than any now projected. Dvali-Gabadadze-Porrati low-curvature modifications of Einstein gravity may also be detected in refined observations in the solar system (Lue and Starkman) or at the intermediate Vainstein scale (Iorio) in isolated galaxy clusters. Dark Energy's epicyclic character, failure to explain the original Cosmic Coincidence (''Why so small now?'') without fine tuning, inaccessibility to laboratory or solar system tests, along with braneworld theories, now motivate future precision solar system, Vainstein-scale and cosmological-scale studies of Dark Gravity. (Orig.)

  3. Chandra Observation of the Interaction of the Radio Source and Cooling Core in Abell 2063

    CERN Document Server

    Kanov, K N; Hicks, A K; Kanov, Kalin N.; Sarazin, Craig L.; Hicks, Amalia K.

    2006-01-01

    We present the results of a Chandra observation of the cooling core cluster Abell 2063. Spectral analysis shows that there is cool gas (2 keV) associated with the cluster core, which is more than a factor of 2 cooler than the outer cluster gas (4.1 keV). There also is spectral evidence for a weak cooling flow, Mdot ~ 20 Msun/yr. The cluster exhibits a complex structure in the center that consists of several bright knots of emission, a depression in the emission to the north of the center of the cluster, and a shell of emission surrounding it. The depression in the X-ray emission is coincident with the position of the north-eastern radio lobe of the radio source associated with the cluster-central galaxy. The shell surrounding this region appears to be hotter, which may be the result of a shock that has been driven into the gas by the radio source. The power output of the radio source appears to be sufficient to offset the cooling flow, and heating of the gas through shocks is a possible explanation of how the...

  4. Chandra Studies of the X-ray gas properties of fossil systems

    Science.gov (United States)

    Qin, Zhen-Zhen

    2016-03-01

    We study ten galaxy groups and clusters suggested in the literature to be “fossil systems (FSs)” based on Chandra observations. According to the M500 - T and LX - T relations, the gas properties of FSs are not physically distinct from ordinary galaxy groups or clusters. We also first study the fgas, 2500 - T relation and find that the FSs exhibit the same trend as ordinary systems. The gas densities of FSs within 0.1r200 are ˜ 10-3 cm-3, which is the same order of magnitude as galaxy clusters. The entropies within 01r200 (S0.1r200) of FSs are systematically lower than those inordinary galaxy groups, which is consistent with previous reports, but we find their S0.1r200 - T relation is more similar to galaxy clusters. The derived mass profiles of FSs are consistent with the Navarro, Frenk and White model in (0.1 - 1)r200, and the relation between scale radius rs and characteristic mass density δc indicates self-similarity of dark matter halos of FSs. The ranges of rs and δc for FSs are also close to those of galaxy clusters. Therefore, FSs share more common characteristics with galaxy clusters. The special birth place of the FS makes it a distinct type of galaxy system.

  5. Cosmology from supernova magnification maps

    CERN Document Server

    Cooray, A R; Huterer, D; Cooray, Asantha; Holz, Daniel

    2006-01-01

    High-z Type Ia supernovae are expected to be gravitationally lensed by the foreground distribution of large-scale structure. The resulting magnification of supernovae is statistically measurable, and the angular correlation of the magnification pattern directly probes the integrated mass density along the line of sight. Measurements of cosmic magnification of supernovae therefore complements galaxy shear measurements in providing a direct measure of clustering of the dark matter. As the number of supernovae is typically much smaller than the number of sheared galaxies, the two-point correlation function of lensed Type Ia supernovae suffers from significantly increased shot noise. Neverthless, we find that the magnification map of a large sample of supernovae, such as that expected from next generation dedicated searches, will be easily measurable and provide an important cosmological tool. For example, a search over 20 sq. deg. over five years leading to a sample of ~ 10,000 supernovae would measure the angul...

  6. Dark matter and cosmological nucleosynthesis

    Science.gov (United States)

    Schramm, D. N.

    1986-01-01

    Existing dark matter problems, i.e., dynamics, galaxy formation and inflation, are considered, along with a model which proposes dark baryons as the bulk of missing matter in a fractal universe. It is shown that no combination of dark, nonbaryonic matter can either provide a cosmological density parameter value near unity or, as in the case of high energy neutrinos, allow formation of condensed matter at epochs when quasars already existed. The possibility that correlations among galactic clusters are scale-free is discussed. Such a distribution of matter would yield a fractal of 1.2, close to a one-dimensional universe. Biasing, cosmic superstrings, and percolated explosions and hot dark matter are theoretical approaches that would satisfy the D = 1.2 fractal model of the large-scale structure of the universe and which would also allow sufficient dark matter in halos to close the universe.

  7. Statistical Inference in Cosmology

    OpenAIRE

    Sellentin, Elena

    2016-01-01

    Analysis of cosmic data is the only way to determine whether General Relativity is the law of gravity also on the largest scales in our Universe. The current standard model of cosmology, ΛCDM, is based on General Relativity, and fits all currently available data flawlessly. However, theoretical dissatisfaction with ΛCDM exists: cosmological data probe gravitational interactions, and ΛCDM fits the data only because it introduces two components of startling gravitional behavio...

  8. Magnetohydrodynamics and Plasma Cosmology

    CERN Document Server

    Kleidis, K; Papadopoulos, D B; Vlahos, L

    2005-01-01

    We study the linear magnetohydrodynamic (MHD) equations, both in the Newtonian and the general-relativistic limit, as regards a viscous magnetized fluid of finite conductivity and discuss instability criteria. In addition, we explore the excitation of cosmological perturbations in anisotropic spacetimes, in the presence of an ambient magnetic field. Acoustic, electromagnetic (e/m) and fast-magnetosonic modes, propagating normal to the magnetic field, can be excited, resulting in several implications of cosmological significance.

  9. Testing cosmological supersymmetry breaking

    CERN Document Server

    Kabat, D; Kabat, Daniel; Rajaraman, Arvind

    2001-01-01

    Banks has proposed a relation between the scale of supersymmetry breaking and the cosmological constant in de Sitter space. His proposal has a natural extension to a general FRW cosmology, in which the supersymmetry breaking scale is related to the Hubble parameter. We study one consequence of such a relation, namely that coupling constants change as the universe evolves. We find that the most straightforward extension of Banks' proposal is disfavored by experimental bounds on variation of the fine structure constant.

  10. Accelerating Cosmologies from Compactification

    CERN Document Server

    Townsend, P K; Townsend, Paul K.; Wohlfarth, Mattias N.R.

    2003-01-01

    A solution of the (4+n)-dimensional vacuum Einstein equations is found for which spacetime is compactified on a compact hyperbolic manifold of time-varying volume to a flat four-dimensional FLRW cosmology undergoing accelerated expansion in Einstein conformal frame. This shows that the `no-go' theorem forbidding acceleration in `standard' (time-independent) compactifications of string/M-theory does not apply to `cosmological' (time-dependent) hyperbolic compactifications.

  11. Cosmological phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Kolb, E.W. [Fermi National Accelerator Lab., Batavia, IL (United States)]|[Chicago Univ., IL (United States)

    1993-10-01

    If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions.

  12. A Planck Vacuum Cosmology

    Directory of Open Access Journals (Sweden)

    Daywitt W. C.

    2009-04-01

    Full Text Available Both the big-bang and the quasi-steady-state cosmologies originate in some type of Planck state. This paper presents a new cosmological theory based on the Planck- vacuum negative-energy state, a state consisting of a degenerate collection of negative- energy Planck particles. A heuristic look at the Einstein field equation provides a con- vincing argument that such a vacuum state could provide a theoretical explanation for the visible universe.

  13. Relativistic Fractal Cosmologies

    OpenAIRE

    Ribeiro, Marcelo B.

    2009-01-01

    This article reviews an approach for constructing a simple relativistic fractal cosmology whose main aim is to model the observed inhomogeneities of the distribution of galaxies by means of the Lemaitre-Tolman solution of Einstein's field equations for spherically symmetric dust in comoving coordinates. This model is based on earlier works developed by L. Pietronero and J.R. Wertz on Newtonian cosmology, whose main points are discussed. Observational relations in this spacetime are presented,...

  14. In Brief: Chandra Observatory marks 10 years in space

    Science.gov (United States)

    Showstack, Randy

    2009-08-01

    NASA's Chandra X-ray Observatory, originally envisioned as a 5-year mission, was deployed into an elliptical orbit around Earth 10 years ago, on 23 July 1999. The most powerful X-ray telescope yet, Chandra has provided a peak into the high-energy universe and has independently confirmed the existence of dark energy. Martin Weisskopf, Chandra project scientist at NASA's Marshall Space Flight Center, Huntsville, Ala., said discoveries made possible by the observatory “have made dramatic changes to our understanding of the universe and its constituents.” “The Great Observatories program—of which Chandra is a major part—shows how astronomers need as many tools as possible to tackle the big questions out there,” said Ed Weiler, associate administrator of NASA's Science Mission Directorate at NASA Headquarters in Washington. The Hubble Space Telescope, Compton Gamma Ray Observatory, and Spitzer Space Telescope are NASA's other Great Observatories. For more information, visit http://chandra.harvard.edu/ten/ and http://chandra.nasa.gov.

  15. Cosmological Models and Stability

    Science.gov (United States)

    Andersson, Lars

    Principles in the form of heuristic guidelines or generally accepted dogma play an important role in the development of physical theories. In particular, philosophical considerations and principles figure prominently in the work of Albert Einstein. As mentioned in the talk by Jiří Bičák at this conference, Einstein formulated the equivalence principle, an essential step on the road to general relativity, during his time in Prague 1911-1912. In this talk, I would like to discuss some aspects of cosmological models. As cosmology is an area of physics where "principles" such as the "cosmological principle" or the "Copernican principle" play a prominent role in motivating the class of models which form part of the current standard model, I will start by comparing the role of the equivalence principle to that of the principles used in cosmology. I will then briefly describe the standard model of cosmology to give a perspective on some mathematical problems and conjectures on cosmological models, which are discussed in the later part of this paper.

  16. [High energy physics and cosmology

    International Nuclear Information System (INIS)

    This research will focus on the implications of recent theories and experiments in high energy physics for the evolution of the early Universe, and on the constraints that cosmological considerations can place on such theories. Several problems are under investigation, including the development of constraints on the inflationary predictions of scale-free primordial fluctuations in a universe at critical closure density by studying their linear and non-linear evolution after they re-enter the particle horizon. We will examine the observable imprint of primordial density fluctuations on the cosmic microwave background radiation in curved cosmological models. Most astronomical evidence points to an open universe: one of our goals is to reconcile this conclusion with the particle physics input. We will investigate the response of the matter distribution to a network of cosmic strings produced during an early symmetry--breaking transition, and compute the resulting cosmic microwave background anisotropies. We will simulate the formation of large--scale structures whose dynamics are dominated by weakly interacting particles such as axions massive neutrinos or photinos in order to model the formation of galaxies, galaxy clusters and superclusters. We will study the distortions in the microwave background radiation, both spectral and angular, that are produced by ionized gas associated with forming clusters and groups of galaxies. We will also study constraints on exotic cooling mechanisms involving axions and majorons set by stellar evolution and the energy input into low mass stars by cold dark matter annihilation in galactic nuclei. We will compute the detailed gamma ray spectrum predicted by various cold dark matter candidates undergoing annihilation in the galactic halo and bulge

  17. High energy physics and cosmology

    International Nuclear Information System (INIS)

    This research will focus on the implications of recent theories and experiments in high energy physics for the evolution of the early Universe, and on the constraints that cosmological considerations can place on such theories. Several problems are under investigation, including the development of constraints on the inflationary predictions of scale--free primordial fluctuations in a universe at critical closure density by studying their linear and non-linear evolution after they re-enter the particle horizon. We will examine the observable imprint of primordial density fluctuations on the cosmic microwave background radiation curved cosmological models. Most astronomical evidence points to an open universe: one of our goals is to reconcile this conclusion with the particle physics input. We will investigate the response of the matter distribution to a network of cosmic strings produced during an early symmetry-breaking transition, and compute the resulting cosmic microwave background anisotropies. We will simulate the formation of large-scale structures whose dynamics are dominated by weakly interacting particles such as axions, massive neutrinos or photinos in order to model the formation of galaxies, galaxy clusters and superclusters. We will study of the distortions in the microwave background radiation, both spectral and angular, that are produced by ionized gas associated with forming clusters and groups of galaxies. We will also study constraints on exotic cooling mechanisms involving axions and majorons set by stellar evolution and the energy input into low mass stars by cold dark matter annihilation galactic nuclei. We will compute the detailed gamma ray spectrum predicted by various cold dark matter candidates undergoing annihilation in the galactic halo and bulge

  18. String cosmology versus standard and inflationary cosmology

    CERN Document Server

    Gasperini, M

    2000-01-01

    This paper presents a review of the basic, model-independent differences between the pre-big bang scenario, arising naturally in a string cosmology context, and the standard inflationary scenario. We use an unconventional approach in which the introduction of technical details is avoided as much as possible, trying to focus the reader's attention on the main conceptual aspects of both scenarios. The aim of the paper is not to conclude in favour either of one or of the other scenario, but to raise questions that are left to the reader's meditation. Warnings: the paper does not contain equations, and is not intended as a complete review of all aspects of string cosmology.

  19. The Tarantula -- Revealed by X-rays (T-ReX): A Definitive Chandra Investigation of 30 Doradus

    Science.gov (United States)

    Townsley, Leisa

    2013-09-01

    30 Doradus is the most important star-forming complex in the Local Group, offering a microscope on starburst astrophysics. At its heart is R136, the most massive resolved stellar cluster, containing the most massive stars known. Across 30 Dor's 250-pc extent, stellar winds and supernovae have carved its ISM into an amazing display of arcs, pillars, and bubbles. So far, Chandra has devoted only 114 ks to this iconic target, limiting our studies just to the most massive stars and large-scale diffuse phenomena. This deep observation will finally exploit Chandra's fine spatial resolution to study ISM interfaces on 1--10 pc scales, the full complement of massive stars, and the brightest pre-main sequence stars that trace 25 Myrs of star formation in this incomparable nearby starburst.

  20. Exploring Bouncing Cosmologies with Cosmological Surveys

    CERN Document Server

    Cai, Yi-Fu

    2014-01-01

    In light of the recent observational data coming from the sky we have two significant directions in the field of theoretical cosmology recently. First, we are now able to make use of present observations, such as the Planck and BICEP2 data, to examine theoretical predictions from the standard inflationary $\\Lambda$CDM which were made decades of years ago. Second, we can search for new cosmological signatures as a way to explore physics beyond the standard cosmic paradigm. In particular, a subset of early universe models admit a nonsingular bouncing solution that attempts to address the issue of the big bang singularity. These models have achieved a series of considerable developments in recent years, in particular in their perturbative frameworks, which made brand-new predictions of cosmological signatures that could be visible in current and forthcoming observations. In this article we present two representative paradigms of very early universe physics. The first is the so-called new matter (or matter-ekpyro...

  1. The Sunyaev-Zeldovich effect and the MITO experiment, a project for cosmological parameters determination

    CERN Document Server

    D'Alba, L; De Petris, M; Orlando, A E; Lamagna, L; Rephaeli, Y; Colafrancesco, Sergio; Signore, M; Kreysa, E; Alba, Livia D'; Melchiorri, Francesco; Petris, Marco De; Orlando, Angiola; Lamagna, Luca; Rephaeli, Yoel; Colafrancesco, Sergio; Signore, Monique; Kreysa, Ernst

    2000-01-01

    Compton scattering of the cosmic microwave background radiation by electrons in the hot gas in clusters of galaxies - the Sunyaev-Zeldovich effect - has long been recognized as a uniquely important feature, rich in cosmological and astrophysical information. Here, we briefly report a theoretical description of this effect. Moreover we discuss the importance to have high-quality clusters X-maps in order to yield an accurate value of the Hubble constant and of other cosmological parameters, strongly preferring nearby clusters observations. Finally we present the MITO experiment, devoted to the observation of the richest nearby cluster, the Coma cluster (A1656).

  2. A giant Ly$\\alpha$ nebula in the core of an X-ray cluster at $z=1.99$: implications for early energy injection

    CERN Document Server

    Valentino, F; Finoguenov, A; Strazzullo, V; Brun, A M C Le; Vignali, C; Bournaud, F; Dickinson, M; Renzini, A; Béthermin, M; Zanella, A; Gobat, R; Cimatti, A; Elbaz, D; Onodera, M; Pannella, M; Sargent, M T; Arimoto, N; Carollo, M; Starck, J-L

    2016-01-01

    We present the discovery of a giant $\\gtrsim$100 kpc Ly$\\alpha$ nebula detected in the core of the X-ray emitting cluster CL J1449+0856 at $z=1.99$ through Keck/LRIS narrow-band imaging. This detection extends the known relation between Ly$\\alpha$ nebulae and overdense regions of the Universe to the dense core of a $5-7\\times10^{13}$ M$_{\\odot}$ cluster. The most plausible candidates to power the nebula are two Chandra-detected AGN host cluster members. Given the physical conditions of the Ly$\\alpha$-emitting gas and the possible interplay with the X-ray phase, we argue that the Ly$\\alpha$ nebula would be short-lived ($\\lesssim10$ Myr) if not continuously replenished with cold gas at a rate of $\\gtrsim1000$ Myr. Cooling from the X-ray phase is disfavored as the replenishing mechanism, primarily because of the high Ly$\\alpha$ to X-ray luminosity ratio ($L_{\\mathrm{Ly\\alpha}}/L_{\\mathrm{X}} \\approx0.3$), $\\gtrsim10-1000\\times$ higher than in local cool-core clusters. Cosmological cold flows are disfavored by cu...

  3. Witnessing galaxy clusters: from maturity to childhood

    CERN Document Server

    Ascaso, Begoña

    2012-01-01

    Galaxy clusters are the largest structures in Universe. They are very important as both cosmological probes and astrophysical laboratories. Several methods have been developed to detect galaxy clusters with different techniques (optical, X-rays, Weak Lensing and Sunyaev-Zeldovich effect) providing cluster samples with a well-characterized purity and completeness rates up to moderate redshift (z$$1.5-2) ever detected. In this talk, I introduce these techniques and review some of the cluster samples obtained including particular striking cases. I discuss their relevance in terms of cosmological and galaxy evolution constraints and finally, I briefly refer to the cluster science predictions for the next generation surveys.

  4. A new multi-scale structure finding algorithm to identify cosmological structure

    Energy Technology Data Exchange (ETDEWEB)

    Snedden, Ali, E-mail: asnedden@nd.edu; Phillips, Lara Arielle; Mathews, Grant J.; Coughlin, Jared; Suh, In-Saeng; Bhattacharya, Aparna

    2015-10-15

    We introduce a new structure finding algorithm that self-consistently parses large scale cosmological structure into clusters, filaments and voids. This structure finding algorithm probes the structure at multiple scales and classifies the appropriate regions with the most probable structure type and size. We show that it can identify the baryon fraction of intercluster medium and cosmological voids.

  5. Chandra Observations of QSO 2237+0305

    CERN Document Server

    Dai, X; Agol, E; Bautz, M W; Garmire, G P

    2003-01-01

    We present the observations of the gravitationally lensed system QSO 2237+0305 performed with the Chandra X-ray Observatory on 2000 Sept. 6, and on 2001 Dec. 8 for 30.3 ks and 9.5 ks, respectively. Imaging analysis resolves the four X-ray images of the Einstein Cross. A possible fifth image is detected; however, this detection less certain. Fits to the combined spectrum of all images of the Einstein Cross assuming a simple power law with Galactic and intervening absorption at the lensing galaxy yield a photon index of 1.90(+0.05,-0.05). For the first observation, this spectral model yields a 0.4-8.0 keV X-ray flux of 4.6e-13 erg cm-2 s-1 and a 0.4-8.0 keV lensed luminosity of 1.0e46 erg s-1. The source exhibits variability both over long and short time scales. The X-ray flux has dropped by 20% between the two observations, and the K-S test showed that image A is variable at the 97% confidence level within the first observation. Furthermore, a possible time-delay of 2.7(+0.5,-0.9) hours between images A and B ...

  6. Deep Chandra observations of Pictor A

    CERN Document Server

    Hardcastle, M J; Birkinshaw, M; Croston, J H; Goodger, J L; Marshall, H L; Perlman, E S; Siemiginowska, A; Stawarz, L; Worrall, D M

    2015-01-01

    We report on deep Chandra observations of the nearby broad-line radio galaxy Pictor A, which we combine with new Australia Telescope Compact Array (ATCA) observations. The new X-ray data have a factor 4 more exposure than observations previously presented and span a 15-year time baseline, allowing a detailed study of the spatial, temporal and spectral properties of the AGN, jet, hotspot and lobes. We present evidence for further time variation of the jet, though the flare that we reported in previous work remains the most significantly detected time-varying feature. We also confirm previous tentative evidence for a faint counterjet. Based on the radio through X-ray spectrum of the jet and its detailed spatial structure, and on the properties of the counterjet, we argue that inverse-Compton models can be conclusively rejected, and propose that the X-ray emission from the jet is synchrotron emission from particles accelerated in the boundary layer of a relativistic jet. For the first time, we find evidence that...

  7. Chandra observations of Cygnus OB2

    CERN Document Server

    Wright, Nicholas J; Drew, Janet E; Vink, Jorick S

    2011-01-01

    Cygnus OB2 is the nearest example of a massive star forming region, containing over 50 O-type stars and hundreds of B-type stars. We have analyzed two Chandra pointings in Cyg OB2, detecting ~1700 X-ray sources, of which ~1450 are thought to be members of the association. Optical and near-IR photometry has been obtained for ~90% of these sources from recent deep Galactic plane surveys. We have performed isochrone fits to the near-IR color-magnitude diagram, deriving ages of 3.5(+0.75,-1.0) and 5.25(+1.5,-1.0) Myrs for sources in the two fields, both with considerable spreads around the pre-MS isochrones. The presence of a second population in the region, somewhat older than the present-day O-type stars, has been suggested by other authors and fits with the ages derived here. The fraction of sources with inner circumstellar disks (as traced by the K-band excess) is found to be very low, but appropriate for a population of age ~5 Myrs. We measure the stellar mass functions and find a power-law slope of Gamma = ...

  8. BOOK REVIEW: Observational Cosmology Observational Cosmology

    Science.gov (United States)

    Howell, Dale Andrew

    2013-04-01

    Observational Cosmology by Stephen Serjeant fills a niche that was underserved in the textbook market: an up-to-date, thorough cosmology textbook focused on observations, aimed at advanced undergraduates. Not everything about the book is perfect - some subjects get short shrift, in some cases jargon dominates, and there are too few exercises. Still, on the whole, the book is a welcome addition. For decades, the classic textbooks of cosmology have focused on theory. But for every Sunyaev-Zel'dovich effect there is a Butcher-Oemler effect; there are as many cosmological phenomena established by observations, and only explained later by theory, as there were predicted by theory and confirmed by observations. In fact, in the last decade, there has been an explosion of new cosmological findings driven by observations. Some are so new that you won't find them mentioned in books just a few years old. So it is not just refreshing to see a book that reflects the new realities of cosmology, it is vital, if students are to truly stay up on a field that has widened in scope considerably. Observational Cosmology is filled with full-color images, and graphs from the latest experiments. How exciting it is that we live in an era where satellites and large experiments have gathered so much data to reveal astounding details about the origin of the universe and its evolution. To have all the latest data gathered together and explained in one book will be a revelation to students. In fact, at times it was to me. I've picked up modern cosmological knowledge through a patchwork of reading papers, going to colloquia, and serving on grant and telescope allocation panels. To go back and see them explained from square one, and summarized succinctly, filled in quite a few gaps in my own knowledge and corrected a few misconceptions I'd acquired along the way. To make room for all these graphs and observational details, a few things had to be left out. For one, there are few derivations

  9. Modern Cosmology: Assumptions and Limits

    Science.gov (United States)

    Hwang, Jai-Chan

    2012-06-01

    Physical cosmology tries to understand the Universe at large with its origin and evolution. Observational and experimental situations in cosmology do not allow us to proceed purely based on the empirical means. We examine in which sense our cosmological assumptions in fact have shaped our current cosmological worldview with consequent inevitable limits. Cosmology, as other branches of science and knowledge, is a construct of human imagination reflecting the popular belief system of the era. The question at issue deserves further philosophic discussions. In Whitehead's words, ``philosophy, in one of its functions, is the critic of cosmologies.'' (Whitehead 1925).

  10. Brightest Cluster Galaxy Identification

    Science.gov (United States)

    Leisman, Luke; Haarsma, D. B.; Sebald, D. A.; ACCEPT Team

    2011-01-01

    Brightest cluster galaxies (BCGs) play an important role in several fields of astronomical research. The literature includes many different methods and criteria for identifying the BCG in the cluster, such as choosing the brightest galaxy, the galaxy nearest the X-ray peak, or the galaxy with the most extended profile. Here we examine a sample of 75 clusters from the Archive of Chandra Cluster Entropy Profile Tables (ACCEPT) and the Sloan Digital Sky Survey (SDSS), measuring masked magnitudes and profiles for BCG candidates in each cluster. We first identified galaxies by hand; in 15% of clusters at least one team member selected a different galaxy than the others.We also applied 6 other identification methods to the ACCEPT sample; in 30% of clusters at least one of these methods selected a different galaxy than the other methods. We then developed an algorithm that weighs brightness, profile, and proximity to the X-ray peak and centroid. This algorithm incorporates the advantages of by-hand identification (weighing multiple properties) and automated selection (repeatable and consistent). The BCG population chosen by the algorithm is more uniform in its properties than populations selected by other methods, particularly in the relation between absolute magnitude (a proxy for galaxy mass) and average gas temperature (a proxy for cluster mass). This work supported by a Barry M. Goldwater Scholarship and a Sid Jansma Summer Research Fellowship.

  11. A Full Year's Chandra Exposure on SDSS Quasars from the Chandra Multiwavelength Project

    CERN Document Server

    Green, Paul J; Richards, G T; Barkhouse, W A; Constantin, A; Haggard, D; Karovska, M; Kim, D -W; Kim, M; Vikhlinin, A; Mossman, A; Silverman, J D; Anderson, S F; Kashyap, V; Wilkes, B J; Tananbaum, H

    2008-01-01

    We study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey (SDSS) that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project (ChaMP). Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.23 QSOs detected, we find no evidence for evolution out to z~5 for either the X-ray photon index Gamma or for the ratio of optical/UV to X-ray flux alpha_ox. About 10% of detected QSOs are obscured (Nh>1E22), but the fraction might reach ~1/3 if most non-detections are absorbed. We confirm a significant correlation between alpha_ox and optical luminosity, but it flattens or disappears for fainter AGN alone. Gamma hardens significantly both towards higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in non-thermal X-ray emission, and our findings thereby strengthen analogies between Galactic black hole binaries and ...

  12. BOOK REVIEW: Cosmology

    Science.gov (United States)

    Silk, Joseph

    2008-11-01

    The field of cosmology has been transformed since the glorious decades of the 1920's and 1930's when theory and observation converged to develop the current model of the expanding universe. It was a triumph of the theory of general relativity and astronomy. The first revolution came when the nuclear physicists entered the fray. This marked the debut of the hot big bang, in which the light elements were synthesized in the first three minutes. It was soon realised that elements like carbon and iron were synthesized in exploding stars. However helium, as well as deuterium and lithium, remain as George Gamow envisaged, the detritus of the big bang. The climax arrived with one of the most remarkable discoveries of the twentieth century, the cosmic microwave background radiation, in 1964. The fossil glow turned out to have the spectrum of an ideal black body. One could not imagine a stronger confirmation of the hot and dense origin of the universe. This discovery set the scene for the next major advance. It was now the turn of the particle physicists, who realized that the energies attained near the beginning of the universe, and unachievable in any conceivable terrestrial accelerator, provided a unique testing ground for theories of grand unification of the fundamental forces. This led Alan Guth and Andrei Linde in 1980 to propose the theory of inflation, which solved outstanding puzzles of the big bang. One could now understand why the universe is so large and homogeneous, and the origin of the seed fluctuations that gave rise to large-scale structure. A key prediction was that the universe should have Euclidean geometry, now verified to a precision of a few percent. Modern cosmology is firmly embedded in particle physics. It merits a text written by a particle physicist who can however appreciate the contributions of astronomy that provide the foundation and infrastructure for the theory of the expanding universe. There are now several such texts available. The most

  13. Thermal Tachyacoustic Cosmology

    CERN Document Server

    Agarwal, Abhineet

    2014-01-01

    An intriguing possibility that can address pathologies in both early universe cosmology (i.e. the horizon problem) and quantum gravity (i.e. non-renormalizability), is that particles at very high energies and/or temperatures could propagate arbitrarily fast. A concrete realization of this possibility for the early universe is the Tachyacoustic (or Speedy Sound) cosmology, which could also produce a scale-invariant spectrum for scalar cosmological perturbations. Here, we study Thermal Tachyacoustic Cosmology (TTC), i.e. this scenario with thermal initial conditions. We find that a phase transition in the early universe, around the scale of Grand Unified Theories (GUT scale; $T\\sim 10^{15}$ GeV), during which the speed of sound drops by $25$ orders of magnitude within a Hubble time, can fit current CMB observations. We further discuss how production of primordial black holes constrains the cosmological acoustic history, while coupling TTC to Horava-Lifshitz gravity leads to a lower limit on the amplitude of ten...

  14. Inhomogeneous anisotropic cosmology

    Science.gov (United States)

    Kleban, Matthew; Senatore, Leonardo

    2016-10-01

    In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.

  15. Evolving Horava Cosmological Horizons

    CERN Document Server

    Fathi, Mohsen

    2016-01-01

    Several sets of radially propagating null congruence generators are exploited in order to form 3-dimensional marginally trapped surfaces, referred to as black hole and cosmological apparent horizons in a Horava universe. Based on this method, we deal with the characteristics of the 2-dimensional space-like spheres of symmetry and the peculiarities of having trapping horizons. Moreover, we apply this method in standard expanding and contracting FLRW cosmological models of a Horava universe to investigate the conditions under which the extra parameters of the theory may lead to trapped/anti-trapped surfaces both in the future and in the past. We also include the cases of negative time, referred to as the finite past, and discuss the formation of anti-trapped surfaces inside the cosmological apparent horizons.

  16. Perfect Quantum Cosmological Bounce

    Science.gov (United States)

    Gielen, Steffen; Turok, Neil

    2016-07-01

    We study quantum cosmology with conformal matter comprising a perfect radiation fluid and a number of conformally coupled scalar fields. Focusing initially on the collective coordinates (minisuperspace) associated with homogeneous, isotropic backgrounds, we are able to perform the quantum gravity path integral exactly. The evolution describes a "perfect bounce", in which the Universe passes smoothly through the singularity. We extend the analysis to spatially flat, anisotropic universes, treated exactly, and to generic inhomogeneous, anisotropic perturbations treated at linear and nonlinear order. This picture provides a natural, unitary description of quantum mechanical evolution across a cosmological bounce. We provide evidence for a semiclassical description in which all fields pass "around" the cosmological singularity along complex classical paths.

  17. Supernovae as cosmological probes

    CERN Document Server

    Nielsen, Jeppe Trost

    2015-01-01

    The cosmological standard model at present is widely accepted as containing mainly things we do not understand. In particular the appearance of a Cosmological Constant, or dark energy, is puzzling. This was first inferred from the Hubble diagram of a low number of Type Ia supernovae, and later corroborated by complementary cosmological probes. Today, a much larger collection of supernovae is available, and here I perform a rigorous statistical analysis of this dataset. Taking into account how the supernovae are calibrated to be standard candles, we run into some subtleties in the analysis. To our surprise, this new dataset - about an order of bigger than the size of the original dataset - shows, under standard assumptions, only mild evidence of an accelerated universe.

  18. General relativity and cosmology

    CERN Document Server

    Bucher, Martin

    2015-01-01

    This year marks the hundredth anniversary of Einstein's 1915 landmark paper "Die Feldgleichungen der Gravitation" in which the field equations of general relativity were correctly formulated for the first time, thus rendering general relativity a complete theory. Over the subsequent hundred years physicists and astronomers have struggled with uncovering the consequences and applications of these equations. This contribution, which was written as an introduction to six chapters dealing with the connection between general relativity and cosmology that will appear in the two-volume book "One Hundred Years of General Relativity: From Genesis and Empirical Foundations to Gravitational Waves, Cosmology and Quantum Gravity," endeavors to provide a historical overview of the connection between general relativity and cosmology, two areas whose development has been closely intertwined.

  19. Cosmology as Geodesic Motion

    CERN Document Server

    Townsend, P K; Townsend, Paul K.; Wohlfarth, Mattias N.R.

    2004-01-01

    For gravity coupled to N scalar fields with arbitrary potential V, it is shown that all flat (homogeneous and isotropic) cosmologies correspond to geodesics in an (N+1)-dimensional `extended target space' of Lorentzian signature (1,N), timelike if V>0 and spacelike if V<0. Accelerating cosmologies correspond to timelike geodesics that lie within an `acceleration subcone' of the `lightcone'. Non-flat (k=-1,+1) cosmologies are shown to evolve as projections of geodesic motion in a space of dimension N+2, of signature (1,N+1) for k=-1 and signature (2,N) for k=+1. We illustrate these results for various potentials of current interest, including exponential and inverse power potentials.

  20. Cosmological Perturbations in Antigravity

    CERN Document Server

    Oltean, Marius

    2014-01-01

    We compute the evolution of cosmological perturbations in a recently proposed Weyl-symmetric theory of two scalar fields with oppositely-signed conformal couplings to Einstein gravity. It is motivated from the minimal conformal extension of the Standard Model, such that one of these scalar fields is the Higgs while the other is a new particle, the dilaton, introduced to make the Higgs mass conformally symmetric. At the background level, the theory admits novel geodesically-complete cyclic cosmological solutions characterized by a brief period of repulsive gravity, or "antigravity", during each successive transition from a Big Crunch to a Big Bang. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, its cosmological solutions are stable at the perturbative level.

  1. The strained state cosmology

    CERN Document Server

    Tartaglia, Angelo

    2015-01-01

    Starting from some relevant facts concerning the behaviour of the universe over large scale and time span, the analogy between the geometric approach of General Relativ- ity and the classical description of an elastic strained material continuum is discussed. Extending the elastic deformation approach to four dimensions it is shown that the accelerated expansion of the universe is recovered. The strain field of space-time repro- duces properties similar to the ones ascribed to the dark energy currently called in to explain the accelerated expansion. The strain field in the primordial universe behaves as radiation, but asymptotically it reproduces the cosmological constant. Subjecting the theory to a number of cosmological tests confirms the soundness of the approach and gives an optimal value for the one parameter of the model, i.e. the bulk modulus of the space-time continuum. Finally various aspects of the Strained State Cosmology (SSC) are discussed and contrasted with some non-linear massive gravity theor...

  2. Deep Chandra observations of Pictor A

    Science.gov (United States)

    Hardcastle, M. J.; Lenc, E.; Birkinshaw, M.; Croston, J. H.; Goodger, J. L.; Marshall, H. L.; Perlman, E. S.; Siemiginowska, A.; Stawarz, Ł.; Worrall, D. M.

    2016-02-01

    We report on deep Chandra observations of the nearby broad-line radio galaxy Pictor A, which we combine with new Australia Telescope Compact Array (ATCA) observations. The new X-ray data have a factor of 4 more exposure than observations previously presented and span a 15 yr time baseline, allowing a detailed study of the spatial, temporal and spectral properties of the AGN, jet, hotspot and lobes. We present evidence for further time variation of the jet, though the flare that we reported in previous work remains the most significantly detected time-varying feature. We also confirm previous tentative evidence for a faint counterjet. Based on the radio through X-ray spectrum of the jet and its detailed spatial structure, and on the properties of the counterjet, we argue that inverse-Compton models can be conclusively rejected, and propose that the X-ray emission from the jet is synchrotron emission from particles accelerated in the boundary layer of a relativistic jet. For the first time, we find evidence that the bright western hotspot is also time-varying in X-rays, and we connect this to the small-scale structure in the hotspot seen in high-resolution radio observations. The new data allow us to confirm that the spectrum of the lobes is in good agreement with the predictions of an inverse-Compton model and we show that the data favour models in which the filaments seen in the radio images are predominantly the result of spatial variation of magnetic fields in the presence of a relatively uniform electron distribution.

  3. Holographic Theory of Gravity and Cosmology

    CERN Document Server

    Ng, Y Jack

    2016-01-01

    According to the holographic principle, the maximum amount of information stored in a region of space scales as the area of its two-dimensional surface, like a hologram. We show that the holographic principle can be understood heuristically as originated from quantum fluctuations of spacetime. Applied to cosmology, this consideration leads to a dynamical cosmological constant $\\Lambda$ of the observed magnitude, in agreement with the result obtained for the present and recent cosmic eras, by using unimodular gravity and causal-set theory. By generalizing the concept of entropic gravity, we find a critical acceleration parameter related to $\\Lambda$ in galactic dynamics, and we construct a phenomenological model of dark matter which we call "modified dark matter" (MDM). We provide successful observational tests of MDM at both the galactic and cluster scales. We also discuss the possibility that the quanta of both dark energy and dark matter obey the quantum Boltzmann statistics or infinite statistics as descri...

  4. Some Dynamical Effects of the Cosmological Constant

    Science.gov (United States)

    Axenides, M.; Floratos, E. G.; Perivolaropoulos, L.

    Newton's law gets modified in the presence of a cosmological constant by a small repulsive term (antigravity) that is proportional to the distance. Assuming a value of the cosmological constant consistent with the recent SnIa data (Λ~=10-52 m-2), we investigate the significance of this term on various astrophysical scales. We find that on galactic scales or smaller (less than a few tens of kpc), the dynamical effects of the vacuum energy are negligible by several orders of magnitude. On scales of 1 Mpc or larger however we find that the vacuum energy can significantly affect the dynamics. For example we show that the velocity data in the local group of galaxies correspond to galactic masses increased by 35% in the presence of vacuum energy. The effect is even more important on larger low density systems like clusters of galaxies or superclusters.

  5. THE SZ EFFECT IN THE PLANCK ERA: ASTROPHYSICAL AND COSMOLOGICAL IMPACT

    Directory of Open Access Journals (Sweden)

    Sergio Colafrancesco

    2013-12-01

    Full Text Available The Sunyaev–Zel’dovich effect (SZE is a relevant probe for cosmology and particle astrophysics. The Planck Era marks a definite step forward in the use of this probe for astrophysics and cosmology. Astrophysical applications to galaxy clusters, galaxies, radiogalaxies and large-scale structures are discussed. Cosmological relevance for the Dark Energy equation of state, modified Gravity scenarios, Dark Matter search, cosmic magnetism and other cosmological applications is also reviewed. Future directions for the study of the SZE and its polarization are finally outlined.

  6. Testing Foundations of Modern Cosmology

    Institute of Scientific and Technical Information of China (English)

    ZHANG Pengjie

    2011-01-01

    1. Introduction Our understanding of the universe has been greatly advanced over the last two decades and a standard cosmology paradigm is now well established. Standard cosmology is based upon the cosmological principle that our universe is statistically homogeneous and isotropic. It is also based upon general relativity with a non-zero cosmological constant. In such a framework, our universe is composed of about 4% ordinary matter (baryonic matter),

  7. Brane cosmology in teleparallel gravity

    CERN Document Server

    Atazadeh, K

    2014-01-01

    We consider cosmology of brane-world scenario in the frame work of teleparallel gravity in that way matter is localized on the brane. We show that the cosmology of such branes is different from the standard cosmology in teleparallelism. In particular, we obtain a class of new solutions with a constant five-dimensional radius and cosmologically evolving brane in the context of constant torsion $f(T)$ gravity.

  8. Relativistic Cosmology Revisited

    Directory of Open Access Journals (Sweden)

    Crothers S. J.

    2007-04-01

    Full Text Available In a previous paper the writer treated of particular classes of cosmological solutions for certain Einstein spaces and claimed that no such solutions exist in relation thereto. In that paper the assumption that the proper radius is zero when the line-element is singular was generally applied. This general assumption is unjustified and must be dropped. Consequently, solutions do exist in relation to the aforementioned types, and are explored herein. The concept of the Big Bang cosmology is found to be inconsistent with General Relativity

  9. Horizons of cosmology

    CERN Document Server

    Silk, Joseph

    2011-01-01

    Horizons of Cosmology: Exploring Worlds Seen and Unseen is the fourth title published in the Templeton Science and Religion Series, in which scientists from a wide range of fields distill their experience and knowledge into brief tours of their respective specialties. In this volume, highly esteemed astrophysicist Joseph Silk explores the vast mysteries and speculations of the field of cosmology in a way that balances an accessible style for the general reader and enough technical detail for advanced students and professionals. Indeed, while the p

  10. The Cosmological Mass Function

    CERN Document Server

    Monaco, P

    1997-01-01

    This thesis aims to review the cosmological mass function problem, both from the theoretical and the observational point of view, and to present a new mass function theory, based on realistic approximations for the dynamics of gravitational collapse. Chapter 1 gives a general introduction on gravitational dynamics in cosmological models. Chapter 2 gives a complete review of the mass function theory. Chapters 3 and 4 present the ``dynamical'' mass function theory, based on truncated Lagrangian dynamics and on the excursion set approach. Chapter 5 reviews the observational state-of-the-art and the main applications of the mass function theories described before. Finally, Chapter 6 gives conclusions and future prospects.

  11. Advances in modern cosmology

    CERN Document Server

    2011-01-01

    The twentieth century elevated our understanding of the Universe from its early stages to what it is today and what is to become of it. Cosmology is the weapon that utilizes all the scientific tools that we have created to feel less lost in the immensity of our Universe. The standard model is the theory that explains the best what we observe. Even with all the successes that this theory had, two main questions are still to be answered: What is the nature of dark matter and dark energy? This book attempts to understand these questions while giving some of the most promising advances in modern cosmology.

  12. Non equilibrium relativistic cosmology

    International Nuclear Information System (INIS)

    A certain systematization through the discussion of results already known on cosmology and the presentation of new ones is given. In section 2 a brief review of the necessary mathematical background is also given. The theory of perturbation of Friedmann-like Universes is presented in section 3. The reduction of Einstein's equations for homogeneous Universes to an autonomous planar system of differential equations is done in section 4. Finally in section 5 the alternative gravitational non-minimal coupling and its consequences to cosmology are discussed. (Author)

  13. Adventures in cosmology

    CERN Document Server

    2012-01-01

    This volume tells of the quest for cosmology as seen by some of the finest cosmologists in the world. It starts with "Galaxy Formation from Start to Finish" and ends with "The First Supermassive Black Holes in the Universe," exploring in between the grand themes of galaxies, the early universe, expansion of the universe, dark matter and dark energy. This up-to-date collection of review articles offers a general introduction to cosmology and is intended for all probing into the profound questions on where we came from and where we are going.

  14. Fourth-rank cosmology

    International Nuclear Information System (INIS)

    Some cosmological implications of the recently proposed fourth-rank theory of gravitation are studied. The model exhibits the possibility of being free from the horizon and flatness problems at the price of introducing a negative pressure. The field equations we obtain are compatible with kobs=0 and Ωobstclas approx. 1020tPlanck approx. 10-23s. When interpreted at the light of General Relativity the treatment is shown to be almost equivalent to that of the standard model of cosmology combined with the inflationary scenario. Hence, an interpretation of the negative pressure hypothesis is provided. (author). 8 refs

  15. Measuring Neutrinos with Cosmology

    Science.gov (United States)

    Knox, Lloyd

    2016-03-01

    Along with a thermal distribution of photons, we expect a thermal distribution of neutrinos to have been produced in the big bang. Although direct detection of the cosmic neutrino background (CNB) is extremely difficult, if not impossible, there is much we are learning indirectly about the CNB from its gravitational influences. I will review constraints from cosmic microwave background observations on the energy density in the CNB, present a recent detection of supersonic evolution of density perturbations in the CNB, and discuss constraints on neutrino masses from cosmological observables. I will also look toward what we can expect from future cosmological surveys, such as CMB-S4.

  16. Observations of the core of the Pleiades with the Chandra X-ray Observatory

    CERN Document Server

    Krishnamurthi, A; Linsky, J L; Martin, E; Gagna, M; Krishnamurthi, Anita; Reynolds, Christopher S; Linsky, Jeffrey L.; Martin, Eduardo; Gagna, Marc

    2001-01-01

    We present results from a 36-ksec observation of the core of the Pleiades open cluster using ACIS-I on the Chandra X-ray Observatory. We have detected 57 sources, most of which do not have previously known optical counterparts. Follow-up photometry indicates that many of the detections are likely to be AGNs, in accordance with extragalactic source counts, but some of the sources may be previously undiscovered low-mass members of the Pleiades. We discuss our dataset and our findings about X-ray emission from early-type stars as well as very late type stars. In particular, the large X-ray fluxes, lack of variability, and hardness ratios of the four Pleiades B6 IV -- F4 V stars suggest a tentative conclusion that Pleiades stars in this spectral type range are intrinsic X-ray sources rather than previously unknown binaries in which the X-ray emission is from a late-type companion. Also the sensitivity of Chandra allowed us to detect nonflare X-ray emission from late-M stars.

  17. Chandra observations of the hyper-luminous infrared galaxy IRAS F15307+3252

    CERN Document Server

    Hlavacek-Larrondo, J; Hogan, M T; Gendron-Marsolais, M -L; Edge, A C; Fabian, A C; Russell, H R; Iwasawa, K; Mezcua, M

    2016-01-01

    Hyper-luminous infrared galaxies (HyLIRGs) lie at the extreme luminosity end of the IR galaxy population with L_IR>10^13L_sun. They are thought to be closer counterparts of the more distant sub-mm galaxies, and should therefore be optimal targets to study the most massive systems in formation. We present deep Chandra observations of IRAS F15307+3252 (100 ks), a classical HyLIRG located at z=0.93, hosting a radio-loud AGN (L_1.4GHz=3.5*10^25 W/Hz). The Chandra X-ray images reveal extended, asymmetric X-ray emission in the soft 0.3-2.0 keV band, extending to 160 kpc in the southern direction. VLA observations at 1.4 GHz and 8.4 GHz reveal no radio counterpart to this extended X-ray emission. The emission is therefore most likely of thermal origin originating from a hot intragroup or intracluster medium virializing in the potential. The temperature (2 keV) and bolometric X-ray luminosity (3*10^43 erg/s) of the gas follow the expected L_X-ray-T correlation for groups and clusters of galaxies. We also find that th...

  18. HDE 245059: A Weak-Lined T Tauri Binary Revealed by Chandra and Keck

    CERN Document Server

    Saavedra, C Baldovin; Duchêne, G; Güdel, M; Skinner, S L; Paerels, F B S; Ghez, A; McCabe, C

    2009-01-01

    We present the Chandra High Energy Transmission Grating Spectrometer (HETGS) and Keck observations of HDE 245059, a young weak-lined T Tauri star (WTTS), member of the pre-main sequence group in the Lambda Orionis Cluster. Our high spatial resolution, near-infrared observations with Keck reveal that HDE 245059 a binary separated by 0.87". Based on this new information we have obtained an estimate of the masses of the binary components; 3M_{sun} and 2.5M_{sun} for the north and south components, respectively. We have estimated the age of the system to be ~2-3 Myr. We detect both components of the binary in the zeroth order Chandra image and in the grating spectra. Our fits to the spectrum of the binary have shown that the emission is dominated by a plasma between 8 and 15 MK, a soft component at 4 MK and a hard component at 50 MK are also detected. The value of the hydrogen column density was low, 8 x 10^{19} cm^{-2}, likely due to the clearing of the inner region of the Lambda Orionis cloud. The abundance pat...

  19. The XBootes Chandra Survey Paper II: The X-ray Source Catalog

    CERN Document Server

    Kenter, A; Forman, W R; Jones, C; Green, P; Kochanek, C S; Vikhlinin, A; Fabricant, D; Fazio, G; Brand, K; Brown, M J I; Dey, A; Jannuzi, B T; Najita, J; McNamara, B; Shields, J; Rieke, M; Kenter, Almus; Murray, Stephen S.; Forman, William R.; Jones, Christine; Green, Paul; Kochanek, Christopher S.; Vikhlinin, Alexey; Fabricant, Daniel; Fazio, Giovani; Brand, Katherine; Brown, Michael J. I.; Dey, Arjun; Jannuzi, Buell T.; Najita, Joan; Namara, Brian Mc; Shields, Joseph; Rieke, Marcia

    2005-01-01

    We present results from a Chandra survey of the nine square degree Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists of 126 separate contiguous ACIS-I observations each of approximately 5000 seconds in duration. These unique Chandra observations allow us to search for large scale structure and to calculate X-ray source statistics o ver a wide, contiguous field of view with arcsecond angular resolution and uniform coverage. Optical spectroscopic follow-up observations and the rich NDWFS data set will allow us to identify and classify these X-ray selected sources. Using wavelet decomposition, we detect 4642 point sources with n $\\ge$ 2 counts. In order to keep our detections ~99% reliable, we limit our list to sources with n $\\ge$ 4 counts. The full 0.5--7 keV band n $\\ge$ 4 count list has 3293 point sources. In addition to the point sources, 43 extended sources have been detected consistent, with the depth of these observations and the number counts of clusters. We present h...

  20. 75 FR 7471 - Chandra Coffee and Rabun Boatworks, Complainants v. Georgia Power Company, Respondent; Notice of...

    Science.gov (United States)

    2010-02-19

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Chandra Coffee and Rabun Boatworks, Complainants v. Georgia Power Company... January 8, 2010, Chandra Coffee and Rabun Boatworks (Complainants) filed with the Federal...