Density and Velocity Fields from the PSCz Survey

We present the results for the predicted density and peculiar velocity fields and the dipole from the PSCz survey of 15,000 IRAS galaxies over 84% of the sky. We find a significant component to the dipole arising between 6000 and 15,000 km/s, but no significant component from greater distances. The misalignment with the CMB is 20 degrees. The most remarkable feature of the PSCz model velocity field is a coherent large-scale flow along the baseline connecting Perseus-Pisces, the Local Supercluster, Great Attractor and the Shapley Concentration. We have measured the parameter beta using the amplitude of the dipole, bulk flow and point by point comparisons between the individual velocities of galaxies in the MarkIII and SFI datasets, and the large-scale clustering distortion in redshift space.All our results are consistent with beta = 0.6 +- 0.1.Comment: 8 pages, 8 figures. To appear in 'Towards an Understanding of Cosmic Flows', Victoria, July 1999, eds Courteau,S., Strauss,M., Willick,J. PAS

Cosmological Parameter Estimation from the CMB

this paper. The modes are optimised for fi, and only the best 320 modes are used. We see that the conditional error in the fi direction is not much worse than the full set, but the likelihood declines slowly along the ridge, and the marginal errors on both fi and \Delta have increased substantially. In the panel bottom left, the SVD procedure has been applied to the union of modes optimised for fi and \Delta, keeping the best 320 modes. The procedure does reasonably well, but in this case the error along the ridge has increased. The bottom right graph shows the result of diagonalizing the Fisher matrix and optimising for the eigenvalue along the ridge. We see excellent behaviour for the best 320 modes, with almost no loss of information compared with the full set. This illustrative example shows how data compression may be achieved with good results by application of a combination of rigorous optimisation and a helping of common sense. 5 Conclusion

Cosmological Parameter Estimation from the CMB

We discuss the problems of applying Maximum Likelihood methods to the CMB and how one can make it both efficient and optimal. The solution is a generalised eigenvalue problem that allows virtually no loss of information about the parameter being estimated, but can allow a substantial compression of the data set. We discuss the more difficult question of simultaneous estimation of many parameters, and propose solutions. A much fuller account of most of this work is available (Tegmark et al. 1997, hereafter TTH). 1 Likelihood Analysis The standard method for extracting cosmological parameters from the CMB is through the use of Maximum Likelihood methods. In general the likelihood function, L, for a set of parameters, θ, is given by a hypothesis, Hx, for the distribution function of the data set. In the case of uniform prior, and assuming a multivariate Gaussian distributed data set consistent with Inflationary models, the a posteriori probability distribution for the parameters is L(θ|x,Hx) = (2π) −n/2 |C(θ) | −1/2 [ exp − 1 2 x † C(θ) −1] x, (1) where θ = (Q,h,Ω0,ΩΛ,Ωb,...) are the usual cosmological parameters we would like to determine. Examples of data are x = ∆T or aℓ,m and the statistics of the n data are fully parametrised by the data covariance matrix, C(θ) = 〈xx † 〉. For simplicity here we assume the data have zero means. 2 Problems with the likelihood method Two important questions we would like to settle about likelihood analysis are (a) is the method optimal in the sense that we get the minimum variance (smallest error bars) for a given amount of data? and (b) is the method efficient – can we realistically find the best-fitting parameters? As an example of this last point, if we have n data points (pixels, harmonic coefficients, etc), and m parameters to estimate with a sampling rate of 1/q, we find that the calculation time scales as τ ∝ q m ×n

Managing personality disorders: the slide to pragmatism

No description supplie

The Cambridge History of Welsh Literature

This is the first comprehensive, single-volume history of the literature of Wales. The volume contains chapters covering the whole range of Welsh literature, from post-Roman Britain to post-devolution Wales, with many of the later chapters providing holistic accounts of literature in Welsh and literature in English within a single genre or a single period of literary production