12 research outputs found
Time-Delay Effect on the cOsmic Background Radiation by Static Gravitational Potential of Clusters
We present a quantitative analysis of the time-delay effect on the cosmic
background radiation (CBR) by static gravitational potential of galaxy
clusters. This is primarily motivated by growing observational evidence that
clusters have essentially experienced no-evolution since redshift ,
indicating that the contribution of a time-dependent potential to CBR
anisotropy discussed in literature could be rather small for the
dynamically-relaxed clusters. Using the softened isothermal sphere model and
the universal density profile for the mass distribution of rich clusters, we
calculate the CBR anisotropy by the time-delay effect and compare it with those
generated by the thermal and kinematic S-Z effects as well as by the transverse
motion of clusters. While it is unlikely that the time-delay effect is
detectable in the current S-Z measurement because of its small amplitude of
- and its achromaticity, it nevertheless leads to an
uncertainty of in the measurement of the kinematic S-Z effect of
clusters. Future cosmological application of the peculiar velocity of clusters
to be measured through the S-Z effect should therefore take this uncertainty
into account.Comment: 15pages,1figures,accepted by Astrophysical Journa
Contributions to the Power Spectrum of Cosmic Microwave Background from Fluctuations Caused by Clusters of Galaxies
We estimate the contributions to the cosmic microwave background radiation
(CMBR) power spectrum from the static and kinematic Sunyaev-Zel'dovich (SZ)
effects, and from the moving cluster of galaxies (MCG) effect. We conclude, in
agreement with other studies, that at sufficiently small scales secondary
fluctuations caused by clusters provide important contributions to the CMBR. At
, these secondary fluctuations become important relative to
lensed primordial fluctuations. Gravitational lensing at small angular scales
has been proposed as a way to break the ``geometric degeneracy'' in determining
fundamental cosmological parameters. We show that this method requires the
separation of the static SZ effect, but the kinematic SZ effect and the MCG
effect are less important. The power spectrum of secondary fluctuations caused
by clusters of galaxies, if separated from the spectrum of lensed primordial
fluctuations, might provide an independent constraint on several important
cosmological parameters.Comment: LateX, 41 pages and 10 figures. Accepted for publication in the
Astrophysical Journa
Extragalactic Foregrounds of the Cosmic Microwave Background: Prospects for the MAP Mission
(Abridged) While the major contribution to the Cosmic Microwave Background
(CMB) anisotropies are the sought-after primordial fluctuations produced at the
surface of last scattering, other effects produce secondary fluctuations at
lower redshifts. Here, we study the extragalactic foregrounds of the CMB in the
context of the upcoming MAP mission. We first survey the major extragalactic
foregrounds and show that discrete sources, the Sunyaev-Zel'dovich (SZ) effect,
and gravitational lensing are the most dominant ones for MAP. We then show that
MAP will detect (>5 sigma) about 46 discrete sources and 10 SZ clusters
directly with 94 GHz fluxes above 2 Jy. The mean SZ fluxes of fainter clusters
can be probed by cross-correlating MAP with cluster positions extracted from
existing catalogs. For instance, a MAP-XBACs cross-correlation will be
sensitive to clusters with S(94GHz)>200mJy, and will thus provide a test of
their virialization state and a measurement of their gas fraction. Finally, we
consider probing the hot gas on supercluster scales by cross-correlating the
CMB with galaxy catalogs. Assuming that galaxies trace the gas, we show that a
cross-correlation between MAP and the APM catalog should yield a marginal
detection, or at least a four-fold improvement on the COBE upper limits for the
rms Compton y-parameter.Comment: 27 LaTeX pages, including 5 ps figures and 2 tables. To appear in
ApJ. Minor revisions to match accepted version. Color figures and further
links available at http://www.astro.princeton.edu/~refreg
Cosmic Microwave Background anisotropies from second order gravitational perturbations
This paper presents a complete analysis of the effects of second order
gravitational perturbations on Cosmic Microwave Background anisotropies, taking
explicitly into account scalar, vector and tensor modes. We also consider the
second order perturbations of the metric itself obtaining them, for a universe
dominated by a collision-less fluid, in the Poisson gauge, by transforming the
known results in the synchronous gauge. We discuss the resulting second order
anisotropies in the Poisson gauge, and analyse the possible relevance of the
different terms. We expect that, in the simplest scenarios for structure
formation, the main effect comes from the gravitational lensing by scalar
perturbations, that is known to give a few percent contribution to the
anisotropies at small angular scales.Comment: 15 pages, revtex, no figures. Version to be published in Phys. Rev.
The Effect of Weak Gravitational Lensing on the Cosmic Microwave Background Anisotropy: Flat versus Open Universes
We have studied the effect of gravitational lensing on the Cosmic Microwave
Background (CMB) anisotropy in flat and open universes. We develop a formalism
to calculate the changes on the radiation power spectrum induced by lensing in
the Newtonian and synchronous-comoving gauges. The previously considered
negligible contribution to the CMB radiation power spectrum of the anisotropic
term of the lensing correlation is shown to be appreciable. However,
considering the nonlinear evolution of the matter power spectrum produces only
slight differences on the results based on linear evolution. The general
conclusion for flat as well as open universes is that lensing slightly smoothes
the radiation power spectrum. For a given range of multipoles the effect of
lensing increases with Omega but for the same acoustic peak it decreases with
. The maximum contribution of lensing to the radiation power spectrum
for is 5% for values in the range 0.1-1.Comment: latex file in ApJ style, 17 pages, 3 ps figure
Non-linear Integrated Sachs-Wolfe Effect
We discuss the non-linear extension to the integrated Sachs-Wolfe effect
(ISW) resulting from the divergence of the large scale structure momentum
density field. The non-linear ISW effect leads to an increase in the total ISW
contribution by roughly two orders of magnitude at l ~ 1000. This increase,
however, is still below the cosmic variance limit of the primary anisotropies;
at further small angular scales, secondary effects such as gravitational
lensing and the kinetic Sunyaev-Zel'dovich (SZ) effect dominates the non-linear
ISW power spectrum. We show this second-order non-linear ISW contribution is
effectively same as the contribution previously described as a lensing effect
due to the transverse motion of gravitational lenses and well known as the
Kaiser-Stebbins effect under the context of cosmic strings. Due to geometrical
considerations, there is no significant three point correlation function, or a
bispectrum, between the linear ISW effects and its non-linear extension. The
non-linear ISW contribution can be potentially used as a probe of the
transverse velocity of dark matter halos such as galaxy clusters. Due to the
small contribution to temperature fluctuations, of order few tenths of micro
Kelvin, however, extrating useful measurements on velocities will be
challenging.Comment: 12 pages, 8 figures; submitted to Phys. Rev.
The integrated Sachs-Wolfe Effect -- Large Scale Structure Correlation
We discuss the correlation between late-time integrated Sachs-Wolfe (ISW)
effect in the cosmic microwave background (CMB) temperature anisotropies and
the large scale structure of the local universe. This correlation has been
proposed and studied in the literature as a probe of the dark energy and its
physical properties. We consider a variety of large scale structure tracers
suitable for a detection of the ISW effect via a cross-correlation. In addition
to luminous sources, we suggest the use of tracers such as dark matter halos or
galaxy clusters. A suitable catalog of mass selected halos for this purpose can
be constructed with upcoming wide-field lensing and Sunyaev-Zel'dovich (SZ)
effect surveys. With multifrequency data, the presence of the ISW-large scale
structure correlation can also be investigated through a cross-correlation of
the frequency cleaned SZ and CMB maps. While convergence maps constructed from
lensing surveys of the large scale structure via galaxy ellipticities are less
correlated with the ISW effect, lensing potentials that deflect CMB photons are
strongly correlated and allow, probably, the best mechanism to study the
ISW-large scale structure correlation with CMB data alone.Comment: 10 Pages, PRD submitte
Higher-Order Gravitational Perturbations of the Cosmic Microwave Background
We study the behavior of light rays in perturbed Robertson-Walker
cosmologies, calculating the redshift between an observer and the surface of
last scattering to second order in the metric perturbation. At first order we
recover the classic results of Sachs and Wolfe, and at second order we
delineate the various new effects which appear; there is no {\it a priori}
guarantee that these effects are significantly smaller than those at first
order, since there are large length scales in the problem which could lead to
sizable prefactors. We find that second order terms of potential observational
interest may be interpreted as transverse and longitudinal lensing by
foreground density perturbations, and a correction to the integrated
Sachs-Wolfe effect.Comment: 21 pages, one figure; minor corrections, new reference