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Research Highlights 2013-14

Includes Planck Satellite science with polarization; black hole simulations; galaxy surveys, dark energy and dark matter; and galaxy formation and evolution

COSMOS consortium researchers have been exploiting the DiRAC HPC Facilities to make progress towards ambitious milestones in five key inter-related areas: (i) extreme universe, (ii) cosmic microwave sky, (iii) dark energy and (iv) galaxy formation and (v) black holes.

Planck Satellite Science with Polarization: The COSMOS Consortium flagship project to analyse and interpret data from ESA’s Planck Satellite has gone forward, building on the success of the 2013 First Data Release, to analyse the Planck Full Mission data with CMB polarisation in results announced in December 2014.  DiRAC resources were used to derive accurate estimates for cosmological parameters, showing interesting deviations from earlier WMAP results, checking consistency with temperature using the polarization data. Planck data was used impose world-leading limits on cosmic non-Gaussianity that substantially constrain inflationary Universe paradigms. The three-point correlator (bispectrum) was evaluated to high precision for the first time in both temperature and polarization (and mixed bispectra) with a wide-ranging model survey undertaken, which yielded tight constraints on standard local, equilateral and orthogonal non-Gaussianity, as well as a measurement of the lensing bispectrum.

CMB combined

CMB temperature (left) and E-mode polarization (right) bispectrum reconstruction obtained from the Planck Full Mission Planck data using the MODAL estimator on COSMOS. Isosurfaces are shown both positive (red) and negative (blue).

Extreme Universe – Black holes: Consortium members continue with world-leading black hole simulations, developing new methods to study black-hole collisions, events so violent their output eclipses the entire electromagnetic universe. Our simulations on Cosmos demonstrate that up to 50% of the total energy can be converted into gravitational waves in such collisions supporting present assumptions in the analysis of collision search experiments at the LHC. We have also been preparing gravitational wave templates for the Advanced LIGO experiment which will begin operating in 2015.  In addition, we have developed and tested a numerical relativity code GRChombo, the first full adaptive mesh refinement code for GR which can be used to simulate black hole collisions and gravitational wave generation in early universe cosmology.

Galaxy surveys, dark energy and dark matter: Consortium resources have been deployed to analyse galaxy surveys through N-body simulations to better understanding the properties of the universe and its perturbations. Much of the focus has been preparing for DES, as well as ambitious future surveys with DESI, Euclid and SKA. Power spectrum measurements from Baryon Oscillation Spectroscopic Survey (BOSS) data and mock catalogues corresponding to the Data Releases 10-12 samples were performed using COSMOS. This usage was acknowledged in three papers: one detailing the mock catalogues (Manera et al, 2014), one looking at the effect of covariance matrix errors (Percival et al, 2014), and the key paper presenting the primary BAO measurements (Anderson et al, 2014). Bayesian analysis of clusters: Planck follow-up has resulted in 99 AMI detections (Ade et al, 2013).

Galaxy formation and evolution: An important uncertainty associated with galaxy modelling is uncertainty about how energy from massive stars and supernovae couples to the surrounding interstellar medium. Identifying powerful new constraints on this uncertain, yet critical, physical process has underpinned recent efforts, work which came to fruition with the realisation that the metal distribution within cosmological simulations, compared with high-redshift observations, provides exactly the constraint that had been missing previously. We have isolated feedback efficiency as the critical controlling factor and demonstrated that highly efficient feedback schemes struggle to explain steep metallicity gradients at high-redshift.