CMB Anisotropies, Large-Scale Structure and the Future

We are now beginning to learn detailed information about cosmological parameters from the shapes of the matter and radiation power spectra, together with their relative normalization. As more high quality data are gathered from galaxy surveys and from microwave anisotropies, the range of allowed models is expected to get incrementally smaller. The amount of information potentially available from a high-resolution satellite experiment should allow a determination of essentially {\it all} currently discussed cosmological parameters to less than ~10%.Comment: 9 pages, including 4 figures in a uuencoded self-unpacking shell script. To appear in Proceedings of the ASP Symposium: Clusters, Lensing and the Future, edited by Virginia Trimbl

Using SCUBA to place upper limits on arcsecond scale CMB anisotropies at 850 microns

The SCUBA instrument on the James Clerk Maxwell Telescope has already had an impact on cosmology by detecting relatively large numbers of dusty galaxies at high redshift. Apart from identifying well-detected sources, such data can also be mined for information about fainter sources and their correlations, as revealed through low level fluctuations in SCUBA maps. As a first step in this direction we analyse a small SCUBA data-set as if it were obtained from a Cosmic Microwave Background (CMB) differencing experiment. This enables us to place limits on CMB anisotropy at 850 microns. Expressed as Q_{flat}, the quadrupole expectation value for a flat power spectrum, the limit is 152 microKelvin at 95 per cent confidence, corresponding to C_0^{1/2} < 355 microKelvin for a Gaussian autocorrelation function, with a coherence angle of about 20--25 arcsec; These results could easily be reinterpretted in terms of any other fluctuating sky signal. This is currently the best limit for these scales at high frequency, and comparable to limits at similar angular scales in the radio. Even with such a modest data-set, it is possible to put a constraint on the slope of the SCUBA counts at the faint end, since even randomly distributed sources would lead to fluctuations. Future analysis of sky correlations in more extensive data-sets ought to yield detections, and hence additional information on source counts and clustering.Comment: 12 pages, 9 postscript figures, uses mn.st

Morphing the CMB: a technique for interpolating power spectra

The confrontation of the Cosmic Microwave Background (CMB) theoretical angular power spectrum with available data often requires the calculation of large numbers of power spectra. The standard practice is to use a fast code to compute the CMB power spectra over some large parameter space, in order to estimate likelihoods and constrain these parameters. But as the dimensionality of the space under study increases, then even with relatively fast anisotropy codes, the computation can become prohibitive. This paper describes the employment of a "morphing" strategy to interpolate new power spectra based on previously calculated ones. We simply present the basic idea here, and illustrate with a few examples; optimization of interpolation schemes will depend on the specific application. In addition to facilitating the exploration of large parameter spaces, this morphing technique may be helpful for Fisher matrix calculations involving derivatives.Comment: 18 pages, including 6 figures, uses elsart.cls, accepted for publication in New Astronomy, changes to match published versio