Cluster Cosmology

h1. Paper pool 2

Interesting papers that are off-topic, controversial or for other reasons not suitable for journal club. We can still discuss them over coffee!

h2. Cosmology and clusters

h3. Excess ellipticity of hot and cold spots in the WMAP data?

Eirik Berntsen, Frode K. Hansen

(Submitted on 22 Nov 2012)

We investigate claims of excess ellipticity of hot and cold spots in the WMAP data (Gurzadyan et al. 2005, 2007). Using the cosmic microwave background data from 7 years of observations by the WMAP satellite, we find, contrary to previous claims of a 10 sigma detection of excess ellipticity in the 3-year data, that the ellipticity of hot and cold spots are perfectly consistent with simulated CMB maps based on the concordance cosmology. We further test for excess obliquity and excess skewness/kurtosis of ellipticity and obliquity and find the WMAP7 data consistent with Gaussian simulated maps.

http://arxiv.org/abs/1211.5275

h2. General interest: Astrophysics

h3. The imminent detection of gravitational waves from massive black-hole binaries with pulsar timing arrays

Sean T. McWilliams, Jeremiah P. Ostriker, Frans Pretorius

(Submitted on 19 Nov 2012)

Recent observations of massive galaxies indicate that they double in mass and quintuple in size between redshift z = 1 and the present, despite undergoing very little star formation, suggesting that galaxy mergers drive the evolution. Since these galaxies will contain supermassive black holes, this suggests a larger black hole merger rate, and therefore a larger gravitational-wave signal, than previously expected. We calculate the merger-driven evolution of the mass function, and find that merger rates are 10 to 30 times higher and gravitational waves are 3 to 5 times stronger than previously estimated, so that the gravitational-wave signal may already be detectable with existing data from pulsar timing arrays. We also provide an explanation for the disagreement with past estimates that were based on dark matter halo simulations.

http://arxiv.org/abs/1211.4590

h2. General interest: Physics

h2. Other