It is now common practice to constrain cosmological parameters using supernovae (SNe) catalogues constructed from several different surveys. Before performing such a joint analysis, however, one ...should check that parameter constraints derived from the individual SNe surveys that make up the catalogue are mutually consistent. We describe a statistically-robust mutual consistency test, which we calibrate using simulations, and apply it to each pairwise combination of the large surveys making up, respectively, the UNION2 catalogue and the very recent JLA (joint light-curve analysis) compilation by Betoule et al. We find no inconsistencies in the latter case, but conclusive evidence for inconsistency between some survey pairs in the UNION2 catalogue.
The form of the primordial power spectrum has the potential to differentiate strongly between competing models of perturbation generation in the early universe and so is of considerable importance. ...The recent release of five years of Wilkinson Microwave Anisotropy Probe observations have confirmed the general picture of the primordial power spectrum as deviating slightly from scale invariance with a spectral tilt parameter of ns∼ 0.96. None the less, many attempts have been made to isolate further features such as breaks and cut-offs using a variety of methods, some employing more than ∼10 varying parameters. In this paper, we apply the robust technique of the Bayesian model selection to reconstruct the optimal degree of structure in the spectrum. We model the spectrum simply and generically as piecewise linear in ln k between ‘nodes’ in k space whose amplitudes are allowed to vary. The number of nodes and their k-space positions are chosen by the Bayesian evidence so that we can identify both the complexity and location of any detected features. Our optimal reconstruction contains, perhaps, surprisingly few features, the data preferring just three nodes. This reconstruction allows for a degree of scale dependence of the tilt with the ‘turn-over’ scale occurring around k∼ 0.016 Mpc−1. More structure is penalized by the evidence as overfitting the data, so there is currently little point in attempting reconstructions that are more complex.
Weak lensing by triaxial galaxy clusters Feroz, F; Hobson, M. P
Monthly notices of the Royal Astronomical Society,
February 2012, Letnik:
420, Številka:
1
Journal Article
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Weak gravitational lensing studies of galaxy clusters often assume a spherical cluster model to simplify the analysis, but some recent studies have suggested this simplifying assumption may result in ...large biases in estimated cluster masses and concentration values, since clusters are expected to exhibit triaxiality. Several such analyses have, however, quoted expressions for the spatial derivatives of the lensing potential in triaxial models, which are open to misinterpretation. In this paper, we give a clear description of weak lensing by triaxial Navarro-Frenk-White (NFW) galaxy clusters and also present an efficient and robust method to model these clusters and obtain parameter estimates. By considering four highly triaxial NFW galaxy clusters, we re-examine the impact of the simplifying assumption of sphericity and find that while the concentration estimates are largely unbiased, except in one of our triaxial NFW simulated clusters, the masses are significantly biased, by up to 40 per cent, for all the clusters we analysed. Moreover, we find that erroneously assuming spherical symmetry can lead to the mistaken conclusion that some substructure is present in the galaxy clusters or, even worse, that multiple galaxy clusters are present in the field. Our cluster fitting method also allows one to answer the question of whether a given cluster exhibits triaxiality or a simple spherical model is good enough.
The oil and gas industry is one of the world’s largest conglomerates, involving the production of complicated and critical methods for refining. This indicates the high necessity for a secure and ...reliable system, such as the Wireless Sensor Network (WSN), which provides auspicious and flexible solutions for the industry. It is one of the most excellent and trendy solutions to the crisis existing within the oil and gas industry, especially in the midstream pipeline. In this application, the nodes were arranged in a linear architecture, to cover a long distance of the pipe. The factors causing the degradation of the overall network performance with increasing density were also identified, due to the increment of the load causing clogging and inhabiting the packet queue. This subsequently led to packet loss, throughput unfairness, higher power consumption, and passive nodes’ presence in the network. The proposed routing protocol (AODVEO) was also reactive based on the AODV reducing the instabilities by splitting the traffic into even and odd paths. Additionally, the performances of AODV and DSDV were used to benchmark the efficacy of the proposed routing protocol.
A hierarchical Bayesian method is applied to the analysis of Type Ia supernovae (SNIa) observations to constrain the properties of the dark matter haloes of galaxies along the SNIa lines of sight via ...their gravitational lensing effect. The full joint posterior distribution of the dark matter halo parameters is explored using the nested sampling algorithm MultiNest, which also efficiently calculates the Bayesian evidence, thereby facilitating robust model comparison. We first demonstrate the capabilities of the method by applying it to realistic simulated SNIa data, based on the real 3-year data release from the Supernova Legacy Survey (SNLS3). Assuming typical values for the parameters in a truncated singular isothermal sphere (SIS) halo model, we find that a catalogue analogous to the existing SNLS3 data set is typically incapable of detecting the lensing signal, but a catalogue containing approximately three times as many SNIa can produce robust and accurate parameter constraints and lead to a clear preference for the SIS halo model over a model that assumes no lensing. In the analysis of the real SNLS3 data, contrary to previous studies, we obtain only a very marginal detection of a lensing signal and weak constraints on the halo parameters for the truncated SIS model, although these constraints are tighter than those typically obtained from equivalent simulated SNIa data sets. This difference is driven by a preferred value of η 1 in the assumed scaling law σ ∝ L
η between velocity dispersion and luminosity, which is somewhat higher than the canonical values of η = ¼ and η = ⅓ for early and late-type galaxies, respectively.
We use a Bayesian software package to analyse CARMA-8 data towards 19 unconfirmed Planck Sunyaev-Zel'dovich-cluster candidates from Rodriguez-Gonzalvez et al. that are associated with significant ...overdensities in WISE. We use two cluster parameterizations, one based on a (fixed shape) generalized-NFW (gNFW) pressure profile and another on a ... gas density profile (with varying shape parameters) to obtain parameter estimates from the CARMA-8 data for the nine CARMA-8-detected clusters. Results from the ... model show that our cluster candidates exhibit a heterogeneous set of brightness-temperature profiles. Comparison of Planck and CARMA-8 measurements show good agreement in Y sub( 500) and an absence of obvious biases. Applying a Planck prior in Y sub( 500) to the CARMA-8 gNFW results reduces uncertainties in Y sub( 500) and ... dramatically (by a factor >4), relative to the independent Planck or CARMA-8 measurements. From this combined analysis, we find that our sample is comprised of massive (Y sub( 500) ranging from 3.3... to 10... x 10 super( -4) arcmin super( 2), sd = 2.2 x 10 super( -4)), relatively compact (... ranging from 2.1... to 5.5... arcmin, sd = 1.0) systems. Spectroscopic Keck/MOSFIRE data confirmed a galaxy member of one of our cluster candidates at z = 0.565. At the preferred photometric redshift of 0.5, we estimate the cluster mass M sub( 500) ... 0.8 plus or minus 0.2 x 10 super( 15) M... We here demonstrate a powerful technique to find massive clusters at intermediate (z ... 0.5) redshifts using a cross-correlation between Planck and WISE data, with high-resolution CARMA-8 follow-up. We also use the combined capabilities of Planck and CARMA-8 to obtain a dramatic reduction, by a factor of several, in parameter uncertainties. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
We present results of a Bayesian analysis of radial velocity data for the star HIP 5158, confirming the presence of two companions and also constraining their orbital parameters. Assuming ...Keplerian orbits, the two-companion model is found to be e48 times more probable than the one-planet model, although the orbital parameters of the second companion are only weakly constrained. The derived orbital periods are 345.6 ± 2.0 and 9017.8 ± 3180.7 d, respectively, and the corresponding eccentricities are 0.54 ± 0.04 and 0.14 ± 0.10. The limits on planetary mass (m sin i) and semimajor axis are (1.44 ± 0.14M
J, 0.89 ± 0.01 au) and (15.04 ± 10.55M
J, 7.70 ± 1.88 au), respectively. Owing to the large uncertainty on the mass of the second companion, we are unable to determine whether it is a planet or a brown dwarf. The remaining ‘noise’ (stellar jitter) unaccounted for by the model is 2.28 ± 0.31 m s−1. We also analysed a three-companion model, but found it to be e8 times less probable than the two-companion model.
Oil and gas industry is one of the largest corporations in the world. The process and machinery involved for the petroleum product to be extracted, refined and transported are usually critical and ...complex. Hence, it is crucial to have a stable and reliable system to control, monitor and manage the security the industrial assets. Since Wireless Sensor Network (WSN) can sense, process and communicate, it is one of the best and popular solution to the problem existed in the oil and gas industry. In this paper, a detailed performance analysis of AODV, DSDV and FIXRT with 32 and 128 packet size is presented by using linear topology in accordance with IEEE 802.11 standards by using ns2.35 simulator. The results showed that FIXRT protocol increases the overall performance of the network by almost 30%.
In the past few decades, sensed data such as wind, vibration, temperature, and humidity were sent through the costly wire cable. With recent advancement and innovation in the wireless field, wireless ...sensor network (WSN) has emerged to benefit many industries in different aspects primarily in term of cost. WSN has been widely used in various applications due to its wide coverage area, particularly in oil and gas facility monitoring. Hence, the usage of grid WSN fits the wide coverage area mainly in the pipeline of downstream of oil and gas process. The main objective of this paper is to give a better understanding of the impact of different packet sizes, routing protocols, and the number of nodes towards a grid WSN as well as to provide open research issues in this field. Two types of routing protocols have been presented in this paper; reactive (AODV) and proactive (DSDV) with different packet sizes using a grid node arrangement. The simulated results have shown that with the increasing size of the network, more performance degradation occurred regardless of the packet size used. This issue can be seen through the packet loss and throughput loss in the network prominently after the deployment of 80 nodes and above. Apart from that, DSDV has shown a better delivery ratio, less number of passive nodes existence and less routing overhead produced in the network as compared to the AODV routing protocol.
We examine the case of neutralino dark matter in the focus point region of the MSSM, in which the scalar sparticles are too heavy to be produced at the LHC. Whilst it has been previously asserted ...that the LHC alone would fail to constrain the properties of the lightest neutralino for such a scenario, we find that one can obtain good predictions of astrophysical quantities such as the relic density, annihilation cross-section and direct search cross-sections by using the shape of the dilepton invariant mass spectrum to constrain neutralino mixing. We demonstrate our technique using a Bayesian analysis of the 24 parameter MSSM model space, and in the process introduce a novel way of improving the LHC results even without assumptions on which new sparticles are responsible for the kinematic features in the dilepton invariant mass distribution. Finally, we consider the interplay between direct search experiments and the LHC, and find that, even with a realistic estimate of the relevant astrophysical uncertainties, one could also combine current direct search exclusion limits with LHC data to constrain neutralino mixing and improve the predicition of other astrophysical quantities.
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