4,451 research outputs found
Lensing Studies with Diffuse Backgrounds
The current weak lensing measurements of the large scale structure are mostly
related to statistical study of background galaxy ellipticities. We consider a
possibility to extend lensing studies with intrinsically unresolved sources and
suggest that spatial fluctuations in the integrated diffuse emission from these
sources can be used for a lensing reconstruction. Examples of upcoming
possibilities include the diffuse background generated by dusty starburst
galaxies at far-infrared wavelengths, first stars and galaxies in near-infrared
wavelengths, and the background related to 21 cm emission by neutral gas in the
general intergalactic medium prior to reionization. While methods developed to
extract lensing information from cosmic microwave background (CMB) temperature
and polarization data can be easily modified to study lensing properties using
diffuse backgrounds at other wavelengths, we suggest that the lensing
extraction from these backgrounds using higher order non-Gaussian clustering
information alone may not be the best approach. In contrast to CMB
anisotropies, reasons for this include the lack of features in the clustering
power spectrum such that the resulting lensing modification to the angular
power spectrum of low-redshift diffuse backgrounds, at arcminute angular
scales, is insignificant. While the use of low redshift backgrounds for lensing
studies will be challenging, due to confusing foregrounds among other reasons,
the use of suggested backgrounds will extend the reconstruction of the
integrated matter power spectrum out to redshifts of 15 to 30, and will bridge
the gap between current and upcoming galaxy lensing studies out to, at most, a
redshift of a few and planned weak lensing studies with CMB out to the last
scattering surface at a redshift of 1100.Comment: 25 pages, 4 figure
Squared temperature-temperature power spectrum as a probe of the CMB bispectrum
It is now well known that mode-coupling effects associated with certain
secondary effects generate higher order correlations in cosmic microwave
background (CMB) temperature anisotropies, beyond the two-point function. In
order to extract the non-Gaussian signal at the three-point level, we suggest a
two-point statistic in the form of an angular power spectrum involving
correlations between squared temperature and temperature anisotropies. This
power spectrum contains compressed information from the bispectrum and can be
easily measured in data with the same techniques that have been considered for
the measurement of the usual temperature-temperature anisotropy power spectrum.
We study the proposed power spectrum resulting from the non-Gaussian signal
generated by correlations involved with gravitational lensing angular
deflections in CMB and the Sunyave-Zel'dovich (SZ) effect due to large scale
pressure fluctuations. Using the Planck frequency cleaned CMB and SZ maps, the
CMB^2-SZ power spectrum provides a direct estimate of the cross-power between
lensing angular deflections and the SZ effect. Through an optimal filter
applied to the squared CMB map, the proposed statistic allows one to obtain all
information from the lensing-SZ bispectrum. The observational measurement of
the lensing-SZ cross-correlation is useful to understand the relation between
large scale structure pressure and dark matter fluctuations.Comment: 9 PRD Pages, 5 figures; Submitted to Phys. Rev.
Non-Gaussian Aspects of Thermal and Kinetic Sunyaev-Zel'dovich Effects
We discuss non-Gaussian effects associated with the local large-scale
structure contributions to the Cosmic Microwave Background (CMB) anisotropies
through the thermal Sunyaev-Zel'dovich (SZ) effect. The non-Gaussianities
associated with the SZ effect arise from the existence of a significant
four-point correlation function in large scale pressure fluctuations. Using the
full covariance matrix of the SZ thermal power spectrum, we study astrophysical
uses of the SZ effect and discuss the extent to which gas properties can be
derived from a measurement of the SZ power spectrum. With the SZ thermal effect
separated in temperature fluctuations using its frequency information, the
kinetic SZ effect is expected to dominate the CMB temperature fluctuations at
small angular scales. The presence of the SZ kinetic effect can be determined
through a cross-correlation between the SZ thermal and a CMB map at small
scales. We suggest a statistic that can be used to study the correlation
between pressure traced by the SZ thermal effect and the baryons traced by the
SZ kinetic effect involving the cross-power spectrum constructed through
squared temperatures instead of the usual temperature itself. Through a
signal-to-noise calculation, we show that future small angular scale
multi-frequency CMB experiments, sensitive to multipoles of a few thousand,
will be able to measure the cross-correlation of SZ thermal and SZ kinetic
effect through a temperature squared power spectrum (abridged).Comment: 27 PRD Pages, 15 figures; Submitted to Phys. Rev.
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