619 research outputs found

    Globular Cluster Systems in Brightest Cluster Galaxies. III: Beyond Bimodality

    Full text link
    We present new deep photometry of the rich globular cluster (GC) systems around the Brightest Cluster Galaxies UGC 9799 (Abell 2052) and UGC 10143 (Abell 2147), obtained with the HST ACS and WFC3 cameras. For comparison, we also present new reductions of similar HST/ACS data for the Coma supergiants NGC 4874 and 4889. All four of these galaxies have huge cluster populations (to the radial limits of our data, comprising from 12000 to 23000 clusters per galaxy). The metallicity distribution functions (MDFs) of the GCs can still be matched by a bimodal-Gaussian form where the metal-rich and metal-poor modes are separated by ~0.8 dex, but the internal dispersions of each mode are so large that the total MDF becomes very broad and nearly continuous from [Fe/H] = -2.4 to Solar. There are, however, significant differences between galaxies in the relative numbers of \emph{metal-rich} clusters, suggesting that they underwent significantly different histories of mergers with massive, gas-rich halos. Lastly, the proportion of metal-poor GCs rises especially rapidly outside projected radii R > 4 R_eff, suggesting the importance of accreted dwarf satellites in the outer halo. Comprehensive models for the formation of GCs as part of the hierarchical formation of their parent galaxies will be needed to trace the systematic change in structure of the MDF with galaxy mass, from the distinctly bimodal form in smaller galaxies up to the broad continuum that we see in the very largest systems.Comment: In press for Astrophysical Journa

    A New Technique for Finding Needles in Haystacks: A Geometric Approach to Distinguishing Between a New Source and Random Fluctuations

    Full text link
    We propose a new test statistic based on a score process for determining the statistical significance of a putative signal that may be a small perturbation to a noisy experimental background. We derive the reference distribution for this score test statistic; it has an elegant geometrical interpretation as well as broad applicability. We illustrate the technique in the context of a model problem from high-energy particle physics. Monte Carlo experimental results confirm that the score test results in a significantly improved rate of signal detection.Comment: 5 pages, 4 figure

    Direct CP violation for Bˉs0K0π+π\bar{B}_{s}^{0}\to K^{0}\pi^{+}\pi^{-} decay in QCD factorization

    Full text link
    In the framework of QCD factorization, based on the first order of isospin violation, we study direct CP violation in the decay of Bˉs0K0ρ0(ω)K0π+π\bar{B}_{s}^{0} \to K^{0}\rho^{0}(\omega)\to K^{0}\pi^{+}\pi^{-} including the effect of ρω\rho-\omega mixing. We find that the CP violating asymmetry is large via ρω\rho-\omega mixing mechanism when the invariant mass of the π+π\pi^{+}\pi^{-} pair is in the vicinity of the ω\omega resonance. For the decay of Bˉs0K0ρ0(ω)K0π+π\bar{B}_{s}^{0} \to K^{0}\rho^{0}(\omega)\to K^{0}\pi^{+}\pi^{-}, the maximum CP violating asymmetries can reach about 46%. We also discuss the possibility to observe the predicted CP violating asymmetries at the LHC

    Statistical Mechanics of the Quantum K-Satisfiability problem

    Full text link
    We study the quantum version of the random KK-Satisfiability problem in the presence of the external magnetic field Γ\Gamma applied in the transverse direction. We derive the replica-symmetric free energy functional within static approximation and the saddle-point equation for the order parameter: the distribution P[h(m)]P[h(m)] of functions of magnetizations. The order parameter is interpreted as the histogram of probability distributions of individual magnetizations. In the limit of zero temperature and small transverse fields, to leading order in Γ\Gamma magnetizations m0m \approx 0 become relevant in addition to purely classical values of m±1m \approx \pm 1. Self-consistency equations for the order parameter are solved numerically using Quasi Monte Carlo method for K=3. It is shown that for an arbitrarily small Γ\Gamma quantum fluctuations destroy the phase transition present in the classical limit Γ=0\Gamma=0, replacing it with a smooth crossover transition. The implications of this result with respect to the expected performance of quantum optimization algorithms via adiabatic evolution are discussed. The replica-symmetric solution of the classical random KK-Satisfiability problem is briefly revisited. It is shown that the phase transition at T=0 predicted by the replica-symmetric theory is of continuous type with atypical critical exponents.Comment: 35 pages, 23 figures; changed abstract, improved discussion in the introduction, added references, corrected typo

    Search for Narrow NNpi Resonances in Exclusive p p -> p p pi+ pi- Measurements

    Get PDF
    Narrow structures in the range of a few MeV have been searched for in p p pi+ and p p pi- invariant mass spectra obtained from exclusive measurements of the p p -> p p pi+ pi- reaction at Tp = 725, 750 and 775 MeV using the PROMICE/WASA detector at CELSIUS. The selected reaction is particularily well suited for the search for NN and / or N Delta decoupled dibaryon resonances. Except for a possible fluctuation at 2087 MeV/c^2 in Mpppi- no narrow structures could be identified neither in Mpppi+ nor in Mpppi- on the 3 sigma level of statistical significance, giving an upper limit (95% C.L.) for dibaryon production in this reaction of sigma < 20 nb for 2020 MeV/c^2 < m(dibaryon) < 2085 MeV/c^2Comment: 3 pages, 4 figure

    Recent AEM Case Study Examples of a Full Waveform Time-Domain System for Near-Surface and Groundwater Applications

    Get PDF
    Early time or high frequency airborne electromagnetic data (AEM) are desirable for shallow sounding or mapping of resistive areas but this poses difficulties due to a variety of issues, such as system bandwidth, system calibration and parasitic loop capacitance. In an effort to address this issue, a continued system design strategy, aimed at improving its early-channel VTEM data, has achieved fully calibrated, quantitative measurements closer to the transmitter current turn-off, while maintaining reasonably optimal deep penetration characteristics. The new design implementation, known as “Full Waveform” VTEM was previously described by Legault et al. (2012). This paper presents some case-study examples of a Full Waveform helicopter time-domain EM system for near-surface application

    Lake Erie hypoxia prompts Canada‐U.S. study

    Full text link
    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95631/1/eost15589.pd
    corecore