47 research outputs found
A critical analysis of high-redshift, massive galaxy clusters: I
We critically investigate current statistical tests applied to high redshift
clusters of galaxies in order to test the standard cosmological model and
describe their range of validity. We carefully compare a sample of
high-redshift, massive, galaxy clusters with realistic Poisson sample
simulations of the theoretical mass function, which include the effect of
Eddington bias. We compare the observations and simulations using the following
statistical tests: the distributions of ensemble and individual existence
probabilities (in the >M,>z sense), the redshift distributions, and the 2d
Kolmogorov-Smirnov test. Using seemingly rare clusters from Hoyle et al.
(2011), and Jee et al. (2011) and assuming the same survey geometry as in Jee
et al. (2011, which is less conservative than Hoyle et al. 2011), we find that
the (>M,>z) existence probabilities of all clusters are fully consistent with
LCDM. However assuming the same survey geometry, we use the 2d K-S test
probability to show that the observed clusters are not consistent with being
the least probable clusters from simulations at >95% confidence, and are also
not consistent with being a random selection of clusters, which may be caused
by the non-trivial selection function and survey geometry. Tension can be
removed if we examine only a X-ray selected sub sample, with simulations
performed assuming a modified survey geometry.Comment: 20 pages, 6 figures, 2 tables, modified to match accepted version
(JCAP); title changed, main analysis unchanged, additional analysi
Feeding your Inflaton: Non-Gaussian Signatures of Interaction Structure
Primordial non-Gaussianity is generated by interactions of the inflaton
field, either self-interactions or couplings to other sectors. These two
physically different mechanisms can lead to nearly indistinguishable bispectra
of the equilateral type, but generate distinct patterns in the relative scaling
of higher order moments. We illustrate these classes in a simple effective
field theory framework where the flatness of the inflaton potential is
protected by a softly broken shift symmetry. Since the distinctive difference
between the two classes of interactions is the scaling of the moments, we
investigate the implications for observables that depend on the series of
moments. We obtain analytic expressions for the Minkowski functionals and the
halo mass function for an arbitrary structure of moments, and use these to
demonstrate how different classes of interactions might be distinguished
observationally. Our analysis casts light on a number of theoretical issues, in
particular we clarify the difference between the physics that keeps the
distribution of fluctuations nearly Gaussian, and the physics that keeps the
calculation under control.Comment: 33 pages (plus appendices), 3 figures. V2: references added, some
minor clarifications. Accepted for publication in JCA