304 research outputs found
A Large Sky Simulation of the Gravitational Lensing of the Cosmic Microwave Background
Large scale structure deflects cosmic microwave background (CMB) photons.
Since large angular scales in the large scale structure contribute
significantly to the gravitational lensing effect, a realistic simulation of
CMB lensing requires a sufficiently large sky area. We describe simulations
that include these effects, and present both effective and multiple plane
ray-tracing versions of the algorithm, which employs spherical harmonic space
and does not use the flat sky approximation. We simulate lensed CMB maps with
an angular resolution of ~0.9 arcmin. The angular power spectrum of the
simulated sky agrees well with analytical predictions. Maps generated in this
manner are a useful tool for the analysis and interpretation of upcoming CMB
experiments such as PLANCK and ACT.Comment: 14 pages, 12 figures, replaced with version accepted for publication
by the AP
Precision cosmology with a combination of wide and deep Sunyaev-Zeldovich cluster surveys
We show the advantages of a wedding cake design for Sunyaev-Zel'dovich
cluster surveys. We show that by dividing up a cluster survey into a wide and a
deep survey, one can essentially recover the cosmological information that
would be diluted in a single survey of the same duration due to the
uncertainties in our understanding of cluster physics. The parameter degeneracy
directions of the deep and wide surveys are slightly different, and combining
them breaks these degeneracies effectively. A variable depth survey with a few
thousand clusters is as effective at constraining cosmological parameters as a
single depth survey with a much larger cluster sample.Comment: 4 figures, 1 table; revised versio
Constraints on neutrino and dark radiation interactions using cosmological observations
Observations of the cosmic microwave background (CMB) and large-scale
structure (LSS) provide a unique opportunity to explore the fundamental
properties of the constituents that compose the cosmic dark radiation
background (CDRB), of which the three standard neutrinos are thought to be the
dominant component. We report on the first constraint to the CDRB rest-frame
sound speed, ceff^2, using the most recent CMB and LSS data. Additionally, we
report improved constraints to the CDRB viscosity parameter, cvis^2. For a
non-interacting species, these parameters both equal 1/3. Using current data we
find that a standard CDRB, composed entirely of three non-interacting neutrino
species, is ruled out at the 99% confidence level (C.L.) with ceff^2 = 0.30
+0.027 -0.026 and cvis^2 = 0.44 +0.27 -0.21 (95% C.L.). We also discuss how
constraints to these parameters from current and future observations (such as
the Planck satellite) allow us to explore the fundamental properties of any
anomalous radiative energy density beyond the standard three neutrinos.Comment: 6 pages, 3 figures, comments welcome; v2: updated with SPT data,
corrected minor typos; v3: version accepted for publication in PR
CMB Lensing and the WMAP Cold Spot
Cosmologists have suggested a number of intriguing hypotheses for the origin
of the "WMAP cold spot", the coldest extended region seen in the CMB sky,
including a very large void and a collapsing texture. Either hypothesis
predicts a distinctive CMB lensing signal. We show that the upcoming generation
of high resolution CMB experiments such as ACT and SPT should be able to detect
the signatures of either textures or large voids. If either signal is detected,
it would have profound implications for cosmology.Comment: 5 pages, 2 figures, a bug in Fig.2 fixe
- …