Astrophysics

A modified version of PQCD considered in previous works is further investigated in the case of a vanishing gluon condensate, by retaining only the quark one. In this case the Green functions generating functional is expressed in a simple form in which Dirac’s delta functions are now absent from the free propagators. The new expansion implements the dimensional transmutation effect through a single interaction vertex in addition to the standard ones in mass less QCD. The results of an ongoing two loop evaluation of the vacuum energy will be presented. The potential is parameterized as a function of the quark mass (defined by the pole of the first corrections to the quark propagator), the assumed finite zero momentum limit of the coupling constant g and the dimensional regularization parameter. The first condensate dependent corrections to the gluon and quark self-energies and propagators are evaluated. Assuming the possibility of fixing a minimum of the potential at the experimental value of the top quark mass =173 GeV, we evaluate the pole of the simplest correction to the propagator of the composite operator describing the quark condensate. Then, alter adopting the idea from the former top condensate models, in which the Higgs field corresponds to the quark condensate, the obtained pole gave a first rough estimate for the Higgs mass =168.2 GeV. Although being inside of the recently experimentally excluded region: 160-170 GeV, this mass value has the chance of being modified by a better approximation being currently considered for the gluon propagator entering its evaluation.

Sunyaev-Zel'dovich Effect (SZE) experiments such as the South Pole Telescope (SPT) are currently surveying a large area of sky searching for clusters via their imprint on the CMB. In order to use the resulting cluster catalogues for cosmology, it is necessary to know the mass- and redshift-dependent cluster selection function. I will describe ongoing work to understand and characterize the current SPT cluster yield, using synthetic SZ sky maps constructed from cosmological simulations and noise models calibrated against SPT data.

The APEX Sunyaev Zel'dovich experiment will be described and its performance since first light in 2006 summarized. Recent results will be presented together with plans for future observations/analysis.

Extracting compact sources from maps contaminated with noise and unwanted astrophysical signals is a well-studied problem. In anticipation of the now-current generation of large-scale SZ surveys, many authors arrived at the conclusion that a simple multi-scale spatial/spectral filter would be the optimal way to find galaxy clusters in data from these surveys. I will briefly present the basics of the spatial/spectral optimal filter and then show in some detail how this has been implemented in one real-world case, namely in data from the South Pole Telescope (SPT) survey.

New high-resolution, cosmological-scale simulations of the microwave sky have been created based on the most recent observational data. Currently these imulations are in use by the ACT team to test their data analysis pipeline. These simulations are also flexible enough to be of use to SPT and Planck. We discuss the various components of the simulations, their construction, and comparison to observational data.

A detailed understanding of galaxy clusters is essential in limiting the potential for systematic effects in the use of galaxy clusters for cosmological measurements. I will synthesize our current work on understanding the stellar components of galaxy clusters, including the intergalactic stellar populations and the structural relationship between stellar populations in galaxies and clusters. Ultimately, the characterization of the relationship between dark matter halos and the stellar populations within them will play a key role in unraveling what clusters tell us about the Universe.

The Red-Sequence Cluster Survey (RCS2) is a 1000-square-degree, multi-color imaging survey carried out using MegaCam on the 3.6m CFHT which is optimized for the search of galaxy clusters with 0.15

The largest structures in the Universe -- Superclusters of Galaxies -- range in size from a few Mpc to the 'Great Walls' scale of hundreds of Mpc. What is the shape of these large structures -- are they filamentary in nature or are they flattened two-dimensional 'pancakes'? How do they form and evolve? Superclusters are typically dominated by clusters of galaxies, systems that serve as one of the most powerful tools in cosmology. What is the shape of clusters -- are they spherically symmetric or are they elongated? Are they aligned with each other on large scales? I present results that answer these fundamental questions, revealing the predicted shape and evolution of the large-scale structure in the Universe in the current popular cosmology. We show that the shape of clusters provides an interesting new tool in constraining cosmology, as well as provides clues to the formation and evolution of large-scale structure.