-
[show abstract]
[hide abstract]
ABSTRACT: We find that the viability of a cosmological model that incorporates 2
sterile neutrinos with masses around 1 eV each, as favored by global neutrino
oscillation analyses including short baseline results, is significantly
dependent on the choice of datasets included in the analysis and the ability to
control the systematic uncertainties associated with these datasets. Our
analysis includes a variety of cosmological probes including the cosmic
microwave background (WMAP7+SPT), Hubble constant (HST), galaxy power spectrum
(SDSS-DR7), and supernova distances (SDSS and Union2 compilations). In the
joint observational analysis, our sterile neutrino model is equally favored as
a LCDM model when using the MLCS light curve fitter for the supernova
measurements, and strongly disfavored by the data at \Delta\chi^2 ~ 18 when
using the SALT2 fitter. When excluding the supernova measurements, the sterile
neutrino model is disfavored by the other datasets at \Delta\chi^2 ~ 12, and at
best becomes mildly disfavored at \Delta\chi^2 ~ 3 when allowing for curvature,
evolving dark energy, additional relativistic species, running of the spectral
index, and freedom in the primordial helium abundance. No single additional
parameter accounts for most of this effect. Therefore, if laboratory
experiments continue to favor a scenario with roughly eV mass sterile
neutrinos, and if this becomes decisively disfavored by cosmology, then a more
exotic cosmological model than explored here may become necessary.
08/2012;
-
Shahab Joudaki
[show abstract]
[hide abstract]
ABSTRACT: From a combination of probes including the cosmic microwave background
(WMAP7+SPT), Hubble constant (HST), baryon acoustic oscillations (SDSS+2dFGRS),
and supernova distances (Union2), we have explored the extent to which the
constraints on the effective number of neutrinos and sum of neutrino masses are
affected by our ignorance of other cosmological parameters, including the
curvature of the universe, running of the spectral index, primordial helium
abundance, evolving late-time dark energy, and early dark energy. In a combined
analysis of the effective number of neutrinos and sum of neutrino masses, we
find mild (2.2 sigma) preference for additional light degrees of freedom.
However, the effective number of neutrinos is consistent with the canonical
expectation of 3 massive neutrinos and no extra relativistic species to within
1 sigma when allowing for evolving dark energy and relaxing the strong
inflation prior on the curvature and running. The agreement improves with the
possibility of an early dark energy component, itself constrained to be less
than 5% of the critical density (95% CL) in our expanded parameter space. In
extensions of the standard cosmological model, the derived amplitude of linear
matter fluctuations sigma_8 is found to closely agree with low-redshift cluster
abundance measurements. The sum of neutrino masses is robust to assumptions of
the effective number of neutrinos, late-time dark energy, curvature, and
running at the level of 1.2 eV (95% CL). The upper bound degrades to 2.0 eV
(95% CL) when further including the early dark energy density and primordial
helium abundance as additional free parameters. Even in extended cosmological
parameter spaces, Planck alone could determine the possible existence of extra
relativistic species at 4 sigma confidence and constrain the sum of neutrino
masses to 0.2 eV (68% CL).
01/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: At high angular frequencies, beyond the damping tail of the primary cosmic microwave background (CMB) power spectrum, the thermal Sunyaev–Zel’dovich (tSZ) effect constitutes the dominant signal in the CMB sky. The tSZ effect is caused by large-scale pressure fluctuations in the baryonic distribution in the universe, such that its statistical properties provide estimates of corresponding properties of the projected 3D pressure fluctuations. The power spectrum of the tSZ is a sensitive probe of the amplitude of density fluctuations, and the bispectrum can be used to separate the bias associated with the pressure. The bispectrum is typically probed with its one-point real-space analogue, the skewness. In addition to the ordinary skewness the morphological properties, as probed by the well-known Minkowski functionals, also require the generalized one-point statistics, which at the lowest order are identical to the generalized skewness parameters. The concept of generalized skewness parameters can be further extended to define a set of three associated generalized skew-spectra. We use these skew-spectra to probe the morphology of the tSZ sky or the y-sky. We show how these power spectra can be recovered from the data in the presence of an arbitrary mask and noise templates using the well known pseudo-Cl approach for arbitrary beam shape. We also employ an approach based on the halo model to compute the tSZ bispectrum. The bispectrum from each of these models is then used to construct the generalized skew-spectra. We consider the performance of an all-sky survey with Planck-type noise and compare the results against a noise-free ideal experiment using a range of smoothing angles. We find that the skew-spectra can be estimated with very high signal-to-noise ratio from future frequency-cleaned tSZ maps that will be available from experiments such as Planck. This will allow their mode-by-mode estimation for a wide range of angular frequencies l and will help us distinguish them from other sources of non-Gaussianity.
Monthly Notices of the Royal Astronomical Society 12/2011; 419(1):138 - 152. · 4.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present novel statistical tools to cross-correlate frequency cleaned
thermal Sunyaev-Zel'dovich (tSZ) maps and tomographic weak lensing (wl)
convergence maps. Moving beyond the lowest order cross-correlation, we
introduce a hierarchy of mixed higher-order statistics, the cumulants and
cumulant correlators, to analyze non-Gaussianity in real space, as well as
corresponding polyspectra in the harmonic domain. Using these moments, we
derive analytical expressions for the joint two-point probability distribution
function (2PDF) for smoothed tSZ (y_s) and convergence (\kappa_s) maps. The
presence of tomographic information allows us to study the evolution of higher
order {\em mixed} tSZ-weak lensing statistics with redshift. We express the
joint PDFs p_{\kappa y}(\kappa_s,y_s) in terms of individual one-point PDFs
(p_{\kappa}(\kappa_s), p_y(y_s)) and the relevant bias functions
(b_{\kappa}(\kappa_s), b_y(y_s)). Analytical results for two different regimes
are presented that correspond to the small and large angular smoothing scales.
Results are also obtained for corresponding {\em hot spots} in the tSZ and
convergence maps. In addition to results based on hierarchical techniques and
perturbative methods, we present results of calculations based on the lognormal
approximation. The analytical expressions derived here are generic and
applicable to cross-correlation studies of arbitrary tracers of large scale
structure including e.g. that of tSZ and soft X-ray background.
11/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: Primordial non-Gaussianity is a crucial test of inflationary cosmology. We consider the impact of non-Gaussianity on the ionization power spectrum from 21 cm emission at the epoch of reionization. We focus on the power spectrum on large scales at redshifts of 7 to 8 and explore the expected constraint on the local non-Gaussianity parameter f(NL) for current and next-generation 21 cm experiments. We show that experiments such as SKA and MWA could measure f(NL) values of order 10. This can be improved by an order of magnitude with a fast-Fourier transform telescope like Omniscope.
Physical Review Letters 09/2011; 107(13):131304. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: At high angular frequencies, beyond the damping tail of the primary power
spectrum, the dominant contribution to the power spectrum of cosmic microwave
background (CMB) temperature fluctuations is the thermal Sunyaev-Zel'dovich
(tSZ) effect. We investigate various important statistical properties of the
Sunyaev-Zel'dovich maps, using well-motivated models for dark matter clustering
to construct statistical descriptions of the tSZ effect to all orders enabling
us to determine the entire probability distribution function (PDF). Any generic
deterministic biasing scheme can be incorporated in our analysis and the
effects of projection, biasing and the underlying density distribution can be
analysed separately and transparently in this approach. We introduce the
cumulant correlators as tools to analyse tSZ catalogs and relate them to
corresponding statistical descriptors of the underlying density distribution.
The statistics of hot spots in frequency-cleaned tSZ maps are also developed in
a self-consistent way to an arbitrary order, to obtain results complementary to
those found using the halo model. We also consider different beam sizes, to
check the extent to which the PDF can be extracted from various observational
configurations. The formalism is presented with two specific models for
underlying matter clustering: (1) the hierarchical ansatz; and (2) the
lognormal distribution. We find both models to be in very good agreement with
the simulation results, though the lognormal model has an edge over the
hierarchical model.
06/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: We forecast the expected cosmological constraints from a combination of
probes of both the universal expansion rate and matter perturbation growth, in
the form of weak lensing tomography, galaxy tomography, supernovae, and the
cosmic microwave background incorporating all cross-correlations between the
observables for an extensive cosmological parameter set. We allow for non-zero
curvature and parameterize our ignorance of the early universe by allowing for
a non-negligible fraction of dark energy (DE) at high redshifts. We find that
early DE density can be constrained to 0.2% of the critical density of the
universe with Planck combined with a ground-based LSST-like survey, while
curvature can be constrained to 0.06%. However, these additional degrees of
freedom degrade our ability to measure late-time dark energy and the sum of
neutrino masses. We find that the combination of cosmological probes can break
degeneracies and constrain the sum of neutrino masses to 0.04 eV, present DE
density also to 0.2% of the critical density, and the equation of state to 0.01
- roughly a factor of two degradation in the constraints overall compared to
the case without allowing for early DE. The constraints for a space-based
mission are similar. Even a modest 1% dark energy fraction of the critical
density at high redshift, if not accounted for in future analyses, biases the
cosmological parameters by up to 2 sigma. Our analysis suggests that throwing
out nonlinear scales (multipoles > 1000) may not result in significant
degradation in future parameter measurements when multiple cosmological probes
are combined. We find that including cross-correlations between the different
probes can result in improved constraints by up to a factor of 2 for the sum of
neutrino masses and early dark energy density.
06/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: The temperature fluctuations and polarization of the Cosmic Microwave
Background (CMB) are now a well-known probe of the Universe at an infant age of
400,000 years. During the transit to us from the surface of last scattering,
the CMB photons are expected to undergo modifications induced by the
intervening large-scale structure. Among the expected secondary effects is the
weak gravitational lensing of the CMB by the foreground dark matter
distribution. We derive a quadratic estimator that uses the non-Gaussianities
generated by the lensing effect at the four-point function level to extract the
power spectrum of lensing potential fluctuations integrated out to z ~ 1100
with peak contributions from potential fluctuations at z of 2 to 3. Using WMAP
7-year temperature maps, we report the first direct constraints of this lensing
potential power spectrum and find that it has an amplitude of A_L = 0.96 +/-
0.60, 1.06 +/- 0.69 and 0.97 +/- 0.47 using the W, V and W+V bands,
respectively.
12/2010;
-
Asantha Cooray,
Steve Eales,
Scott Chapman,
David L. Clements,
Olivier Dore,
Duncan Farrah,
Matt J. Jarvis,
Manoj Kaplinghat,
Mattia Negrello,
Alessandro Melchiorri, [......],
Licia Verde,
Aprajita Verma,
Patricio Vielva,
Marco P. Viero,
Baltasar Vila Vilaro,
Julie Wardlow,
Grant Wilson,
Edward L. Wright,
C. Kevin Xu,
Min S. Yun
[show abstract]
[hide abstract]
ABSTRACT: A large sub-mm survey with Herschel will enable many exciting science opportunities, especially in an era of wide-field optical and radio surveys and high resolution cosmic microwave background experiments. The Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron, respectively, in the southern hemisphere (3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which have extensive multi-wavelength coverage and are easily accessible from ALMA. Two thirds of the of the sources are expected to be at z > 1, one third at z > 2 and about a 1000 at z > 5. (b) Remove point source confusion in secondary anisotropy studies with Planck and ground-based CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources leading to a 2% test of general relativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an unbiased study of the environmental dependence of star formation. (e) Perform an unbiased survey for star formation and dust at high Galactic latitude and make a census of debris disks and dust around AGB stars and white dwarfs. Comment: White paper supplement to the proposal submitted by the HSLS science team to ESA for Herschel open-time programs
07/2010;
-
Asantha Cooray,
Steve Eales,
Scott Chapman,
David L. Clements,
Olivier Dore,
Duncan Farrah,
Matt J. Jarvis,
Manoj Kaplinghat,
Mattia Negrello,
Alessandro Melchiorri, [......],
Licia Verde,
Aprajita Verma,
Patricio Vielva,
Marco P. Viero,
Baltasar Vila Vilaro,
Julie Wardlow,
Grant Wilson,
Edward L. Wright,
C. Kevin Xu,
Min S. Yun
[show abstract]
[hide abstract]
ABSTRACT: A large sub-mm survey with Herschel will enable many exciting science
opportunities, especially in an era of wide-field optical and radio
surveys and high resolution cosmic microwave background experiments. The
Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000
sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a)
produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy
(50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron,
respectively, in the southern hemisphere (3000 sq. degrees) and in an
equatorial strip (1000 sq. degrees), areas which have extensive
multi-wavelength coverage and are easily accessible from ALMA. Two
thirds of the of the sources are expected to be at z > 1, one third
at z > 2 and about a 1000 at z > 5. (b) Remove point source
confusion in secondary anisotropy studies with Planck and ground-based
CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources
leading to a 2% test of general relativity. (d) Identify 200
proto-cluster regions at z of 2 and perform an unbiased study of the
environmental dependence of star formation. (e) Perform an unbiased
survey for star formation and dust at high Galactic latitude and make a
census of debris disks and dust around AGB stars and white dwarfs.
06/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: The Sunyaev-Zel'dovich (SZ) effect has a distinct spectral signature that
allows its separation from fluctuations in the cosmic microwave background
(CMB) and foregrounds. Using CMB anisotropies measured in Wilkinson Microwave
Anisotropy Probe's five-year maps, we constrain the SZ fluctuations at large,
degree angular scales corresponding to multipoles in the range from 10 to 400.
We provide upper bounds on SZ fluctuations at multipoles greater than 50, and
find evidence for a hemispherically asymmetric signal at ten degrees angular
scales. The amplitude of the detected signal cannot be easily explained with
the allowed number density and temperature of electrons in the Galactic halo.
We have failed to explain the excess signal as a residual from known Galactic
foregrounds or instrumental uncertainties such as 1/f-noise.
02/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: We consider corrections to the underlying cosmology due to secondary contributions from weak gravitational lensing, the integrated Sachs-Wolfe effect, and the Sunyaev-Zel'dovich effect contained in the trispectrum. We incorporate these additional contributions to the covariance of a binned angular power spectrum of temperature anisotropies in the analysis of current and prospective data sets. Although recent experiments such as ACBAR and CBI are not particularly sensitive to these additional non-Gaussian effects, the interpretation of Planck and CMBPol anisotropy spectra will require an accounting of non-Gaussian covariance leading to a degradation in cosmological parameter estimates by up to 20% and 30%, respectively. Comment: 9 pages. Fixed some typos
09/2009;
-
[show abstract]
[hide abstract]
ABSTRACT: We examine the influence of percent-level dark energy corrections to the nonlinear matter power spectrum on constraints of the dark energy equation of state from future weak lensing probes. We explicitly show that a poor approximation (off by > 10%) to the nonlinear corrections causes a > 1 sigma bias on the determination of the dark energy equation of state. Future weak lensing surveys must therefore incorporate dark energy modifications to the nonlinear matter power spectrum accurate to the percent-level, to avoid introducing significant bias in their measurements. For the WMAP5 cosmology, the more accurate power spectrum is more sensitive to dark energy properties, resulting in a factor of two improvement in dark energy equation of state constraints. We explore the complementary constraints on dark energy from future weak lensing and supernova surveys. A space-based, JDEM-like survey measures the equation of state in five independent redshift bins to ~10%, while this improves to ~5% for a wide-field ground-based survey like LSST. These constraints are contingent upon our ability to control weak lensing systematic uncertainties to the sub-percent level. Comment: 12 pages, 12 figures. Typo in Eqn 8 corrected
04/2009;
-
[show abstract]
[hide abstract]
ABSTRACT: Our ignorance of dark energy is generally described by a two-parameter equation of state. In these approaches, a particular ad hoc functional form is assumed, and only two independent parameters are incorporated. We propose a model-independent, multiparameter approach to fitting dark energy and show that next-generation surveys will constrain the equation of state in three or more independent redshift bins to better than 10%. Future knowledge of dark energy will surpass two numbers (e.g., [w{0},w{1}] or [w{0},w{a}]), and we propose a more flexible approach to the analysis of present and future data.
Physical Review Letters 06/2008; 100(24):241302. · 7.37 Impact Factor
-
Asantha Cooray,
Steve Eales,
Scott Chapman,
David L Clements,
Olivier Dore,
Duncan Farrah,
Matt J Jarvis,
Manoj Kaplinghat,
Mattia Negrello,
Alessandro Melchiorri, [......],
Licia Verde,
Aprajita Verma,
Patricio Vielva,
Marco P Viero,
Baltasar Vila Vilaro,
Julie Wardlow,
Grant Wilson,
Edward L Wright,
Kevin C Xu,
Min S Yun
[show abstract]
[hide abstract]
ABSTRACT: A large sub-mm survey with Herschel will enable many exciting science opportunities, especially in an era of wide-field optical and radio surveys and high resolution cosmic microwave background experiments. The Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron, respectively, in the southern hemisphere (3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which have extensive multi-wavelength coverage and are easily accessible from ALMA. Two thirds of the of the sources are expected to be at z ensuremath> 1, one third at z ensuremath> 2 and about a 1000 at z ensuremath> 5. (b) Remove point source confusion in secondary anisotropy studies with Planck and ground-based CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources leading to a 2% test of general relativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an unbiased study of the environmental dependence of star formation. (e) Perform an unbiased survey for star formation and dust at high Galactic latitude and make a census of debris disks and dust around AGB stars and white dwarfs.
