Abstract. It has recently been suggested by Luminet et al. (2003) that the WMAP data are better matched by a geometry in which the topology is that of a Poincaré dodecahedral model and the curvature is "slightly" spherical, rather than by an (effectively) infinite flat model. A general back-to-back matched circles analysis by Cornish et al. (2004) for angular radii in the range 25−90• , using a correlation statistic for signal detection, failed to support this. In this paper, a matched circles analysis specifically designed to detect dodecahedral patterns of matched circles is performed over angular radii in the range 1−40• on the oneyear WMAP data. Signal detection is attempted via a correlation statistic and an rms difference statistic. Extreme value distributions of these statistics are calculated for one orientation of the 36• "screw motion" (Clifford translation) when matching circles, for the opposite screw motion, and for a zero (unphysical) rotation. The most correlated circles appear for circle radii of α = 11 ± 1• , for the left-handed screw motion, but not for the right-handed one, nor for the zero rotation. The favoured six dodecahedral face centres in galactic coordinates are (l• ) and their opposites. The six pairs of circles independently each favour a circle angular radius of 11 ± 1• . The temperature fluctuations along the matched circles are plotted and are clearly highly correlated. Whether or not these six circle pairs centred on dodecahedral faces match via a 36• rotation only due to unexpected statistical properties of the WMAP ILC map, or whether they match due to global geometry, it is clear that the WMAP ILC map has some unusual statistical properties which mimic a potentially interesting cosmological signal.

It has been suggested by Roukema and coworkers (hereafter R04) that the topology of the Universe as probed by the "matched circles" method using the first year release of the WMAP CMB data, might be that of the Poincaré dodecahedral space (PDS) model. An excess in the correlation of the "identified circles" was reported by R04, for circles of angular radius of ∼11• for a relative phase twist −36• , hinting that this could be due to a Clifford translation, if the hypothesized model were true. R04 did not however specify the statistical significance of the correlation signal. We investigate the statistical significance of the signal using Monte Carlo CMB simulations in a simply connected Universe, and present an updated analysis using the three-year WMAP data. We find that our analyses of the first and three year WMAP data provide results that are consistent with the simply connected space at a confidence level as low as 68%.

We re-examine the evidence of hemispherical power asymmetry, detected in the cosmic microwave background (CMB) WMAP (Wilkinson Microwave Anisotropy Probe) data using a new method. We use a data filtering, preprocessing , and a statistical approach different from those used previously, and pursue an independent method of parameter estimation. First, we analyze the hemispherical variance ratios and compare these with simulated distributions. Secondly, working within a previously proposed CMB bipolar modulation model, we constrain the model parameters: the amplitude and the orientation of the modulation field as a function of various multipole bins. Finally, we select three ranges of multipoles leading to the most anomalous signals, and we process corresponding 100 Gaussian, random field (GRF) simulations, treated as observational data, to further test the statistical significance and robustness of the hemispherical power asymmetry. For our analysis we use the Internally-Linearly-Coadded (ILC) full sky map, and the KQ75 cut sky V channel foregrounds reduced map of the WMAP five year data (V5). We constrain the modulation parameters using a generic maximum a posteriori method.In particular, we find differences in hemispherical power distribution, which when described in terms of a model with bipolar modulation field, exclude the field amplitude value of the isotropic model A = 0 at confidence level of ∼ 99.5% ( ∼ 99.4%) in the multipole range ℓ ∈ [7, 19] (ℓ ∈ [7, 79]) in the V5 data, and at the confidence level ∼ 99.9% in the multipole range ℓ ∈ [7, 39] in the ILC5 data, with the best fit (modal PDF) values in these particular multipole ranges of A = 0.21 (A = 0.21) and A = 0.15 respectively.However, we also point out that similar or larger significances (in terms of rejecting the isotropic model), and large best-fit modulation amplitudes are obtained in GRF simulations as well, which reduces the overall significance of the CMB power asymmetry down to only about 94% (95%) in the V5 data, in the range ℓ ∈ [7, 19] (ℓ ∈ [7, 79]).

We introduce and analyze a method for testing statistical isotropy and Gaussianity and apply it to the Wilkinson Microwave Anisotropy Probe (WMAP) cosmic microwave background (CMB) foreground reduced temperature maps. We also test cross-channel difference maps to constrain levels of residual foreground contamination and systematic uncertainties. We divide the sky into regions of varying size and shape and measure the first four moments of the one-point distribution within these regions, and using their simulated spatial distributions we test the statistical isotropy and Gaussianity hypotheses. By randomly varying orientations of these regions, we sample the underlying CMB field in a new manner, that offers a richer exploration of the data content, and avoids possible biasing due to a single choice of sky division. In our analysis we account for all two-point correlations between different regions and also show the impact on the results when these correlations are neglected. The statistical significance is assessed via comparison with realistic Monte Carlo simulations. We find the three-year WMAP maps to agree well with the isotropic, Gaussian random field simulations as probed by regions corresponding to the angular scales ranging from 6° to 30° at 68% confidence level (CL). We report a strong, anomalous (99.8% CL) dipole ‘excess’ in the V band of the three-year WMAP data and also in the V band of the WMAP five-year data (99.3% CL). Using our statistics, we notice large scale hemispherical power asymmetry, and find that it is not highly statistically significant in the WMAP three-year data () at scales . The significance is even smaller if multipoles up to are considered (∼90% CL). We give constraints on the amplitude of the previously proposed CMB dipole modulation field parameter. We find some hints of foreground contamination in the form of a locally strong, anomalous kurtosis excess in the Q+V +W co-added map, which however is not significant globally. We easily detect the residual foregrounds in cross-band difference maps at rms level (at scales ) and limit the systematical uncertainties to (at scales ).

We present 30-GHz Sunyaev-Zel'dovich (SZ) observations of a statistically complete sample of galaxy clusters with the One Centimetre Receiver Array-prototype (OCRA-p). The clusters are the 18 most X-ray luminous clusters at z > 0.2 in the ROSAT Brightest Cluster Sample. We correct for contaminant radio sources via supplementary observations with the Green Bank Telescope, also at 30 GHz, and remove a cluster that is contaminated by an unresolved X-ray source. All 17 remaining clusters have central SZ effects with Comptonization parameter y 0 exceeding 1.9 × 10 −4 , and 13 are detected at significance ≥3σ . We use our data to examine scalings between y 0 and X-ray temperature, X-ray luminosity and the X-ray mass proxy Y X , and find good agreement with predictions from self-similar models of cluster formation, with an intrinsic scatter in y 0 of about 25 per cent. We also comment on the success of the observations in the face of the contaminant source population, and the implications for upcoming cm-wave surveys.

We investigate the effectiveness of blind surveys for radio sources and galaxy cluster thermal Sunyaev-Zel'dovich effects (TSZEs) using the four-pair, beam-switched OCRA-f radiometer on the 32-m radio telescope in Poland. The predictions are based on mock maps that include the cosmic microwave background, TSZEs from hydrodynamical simulations of large scale structure formation, and unresolved radio sources. We validate the mock maps against observational data, and examine the limitations imposed by simplified physics. We estimate the effects of source clustering towards galaxy clusters from NVSS source counts around Planck-selected cluster candidates, and include appropriate correlations in our mock maps. The study allows us to quantify the effects of halo line-of-sight alignments, source confusion, and telescope angular resolution on the detections of TSZEs.We perform a similar analysis for the planned 100-m Hevelius radio telescope (RTH) equipped with a 49beam radio camera and operating at frequencies up to 22 GHz.We find that RT32/OCRA-f will be suitable for small-field blind radio source surveys, and will detect 33 +17 −11 new radio sources brighter than 0.87 mJy at 30 GHz in a 1 deg 2 field at > 5σ CL during a one-year, noncontinuous, observing campaign, taking account of Polish weather conditions. It is unlikely that any galaxy cluster will be detected at 3σ CL in such a survey. A 60-deg 2 survey, with field coverage of 2 2 beams per pixel, at 15 GHz with the RTH, would find < 1.5 galaxy clusters per year brighter than 60 µJy (at 3σ CL), and would detect about 3.4 × 10 4 point sources brighter than 1 mJy at 5σ CL, with confusion causing flux density errors 2% (20%) in 68% (95%) of the detected sources. A primary goal of the planned RTH will be a wide-area (π sr) radio source survey at 15 GHz. This survey will detect nearly 3 × 10 5 radio sources at 5σ CL down to 1.3 mJy, and tens of galaxy clusters, in one year of operation with typical weather conditions. Confusion will affect the measured flux densities by 1.5% (16%) for 68% (95%) of the point sources. We also gauge the impact of the RTH by investigating its performance if equipped with the existing RT32 receivers, and the performance of the RT32 equipped with the RTH radio camera.

Over the last few years a number of software and hardware improvements have been implemented to the 32-m Cassegrain radio telescope located near Toruń. The 19-bit angle encoders have been upgraded to 29-bit in azimuth and elevation axes. The control system has been substantially improved, in order to account for a number of previously-neglected, astrometric effects that are relevant for milli-degree pointing. In the summer 2015, as a result of maintenance works, the orientation of the secondary mirror has been slightly altered, which resulted in worsening of the pointing precision, much below the nominal telescope capabilities. In preparation for observations at the highest available frequency of 30-GHz, we use One Centimeter Receiver Array (OCRA), to take the most accurate pointing data ever collected with the telescope, and we analyze it in order to improve the pointing precision. We introduce a new generalized pointing model that, for the first time, accounts for the rail irregularities, and we show that the telescope can have root mean square pointing accuracy at the level <8 and <12 in azimuth and elevation respectively. Finally, we discuss the implemented pointing improvements in the light of effects that may influence their long-term stability.

We utilise ground-based, balloon-borne and satellite climatology data to reconstruct site and season-dependent vertical profiles of precipitable water vapour (PWV). We use these profiles to solve radiative transfer through the atmosphere, and derive atmospheric brightness temperature (T atm ) and optical depth (τ ) at centimetre wavelengths.We validate the reconstruction by comparing the model column PWV with photometric measurements of PWV, performed in clear sky conditions pointed towards the Sun. Based on the measurements, we devise a selection criteria to filter the climatology data to match the PWV levels to the expectations of the clear sky conditions.We apply the reconstruction to the location of a Polish 32-metre radio telescope, and characterise T atm and τ year-round, at selected frequencies. We also derive the zenith distance dependence for these parameters, and discuss the shortcomings of using planar, single-layer, and optically thin atmospheric models in continuum radio-source flux-density measurement calibrations.We obtain PWV-T atm and PWV-τ scaling relations in clear sky conditions, and constrain limits to which the actual T atm and τ can deviate from those derived solely from the climatological data.Finally, we suggest a statistical method to detect clear sky that involves groundlevel measurements of relative humidity. Accuracy is tested using local climatological data. The method may be useful to constrain cloud cover in cases when no other (and more robust) climatological data are available.