333 research outputs found
Can inflationary models of cosmic perturbations evade the secondary oscillation test?
We consider the consequences of an observed Cosmic Microwave Background (CMB)
temperature anisotropy spectrum containing no secondary oscillations. While
such a spectrum is generally considered to be a robust signature of active
structure formation, we show that such a spectrum {\em can} be produced by
(very unusual) inflationary models or other passive evolution models. However,
we show that for all these passive models the characteristic oscillations would
show up in other observable spectra. Our work shows that when CMB polarization
and matter power spectra are taken into account secondary oscillations are
indeed a signature of even these very exotic passive models. We construct a
measure of the observability of secondary oscillations in a given experiment,
and show that even with foregrounds both the MAP and \pk satellites should be
able to distinguish between models with and without oscillations. Thus we
conclude that inflationary and other passive models can {\em not} evade the
secondary oscillation test.Comment: Final version accepted for publication in PRD. Minor improvements
have been made to the discussion and new data has been included. The
conclusions are unchagne
CMBfit: Rapid WMAP likelihood calculations with normal parameters
We present a method for ultra-fast confrontation of the WMAP cosmic microwave
background observations with theoretical models, implemented as a publicly
available software package called CMBfit, useful for anyone wishing to measure
cosmological parameters by combining WMAP with other observations. The method
takes advantage of the underlying physics by transforming into a set of
parameters where the WMAP likelihood surface is accurately fit by the
exponential of a quartic or sextic polynomial. Building on previous physics
based approximations by Hu et.al., Kosowsky et.al. and Chu et.al., it combines
their speed with precision cosmology grade accuracy. A Fortran code for
computing the WMAP likelihood for a given set of parameters is provided,
pre-calibrated against CMBfast, accurate to Delta lnL ~ 0.05 over the entire
2sigma region of the parameter space for 6 parameter ``vanilla'' Lambda CDM
models. We also provide 7-parameter fits including spatial curvature,
gravitational waves and a running spectral index.Comment: 14 pages, 8 figures, References added, accepted for publication in
Phys.Rev.D., a Fortran code can be downloaded from
http://space.mit.edu/home/tegmark/cmbfit
Cosmic microwave background anisotropy power spectrum statistics for high precision cosmology
As the era of high precision cosmology approaches, the empirically determined
power spectrum of the microwave background anisotropy, , will provide a
crucial test for cosmological theories. We present a unified semi-analytic
framework for the study of the statistical properties of the coefficients
computed from the results of balloon, ground based, and satellite experiments.
An illustrative application shows that commonly used approximations {\it bias}
the estimation of the baryon parameter at the 1% level even for a
satellite capturing as much as % of the sky.Comment: 4 pages, 3 figures. Also available at
http://www.tac.dk/~wandelt/downloads.htm
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
Density pertubation of unparticle dark matter in the flat Universe
The unparticle has been suggested as a candidate of dark matter. We
investigated the growth rate of the density perturbation for the unparticle
dark matter in the flat Universe. First, we consider the model in which
unparticle is the sole dark matter and find that the growth factor can be
approximated well by , where is
the equation of state of unparticle. Our results show that the presence of
modifies the behavior of the growth factor . For the second model
where unparticle co-exists with cold dark matter, the growth factor has a new
approximation and
is a function of . Thus the growth factor of unparticle is quite
different from that of usual dark matter. These information can help us know
more about unparticle and the early evolution of the Universe.Comment: 6pages, 4 figures, accepted for publication in Eur. Phys. J.
Limits on the gravity wave contribution to microwave anisotropies
We present limits on the fraction of large angle microwave anisotropies which
could come from tensor perturbations. We use the COBE results as well as
smaller scale CMB observations, measurements of galaxy correlations, abundances
of galaxy clusters, and Lyman alpha absorption cloud statistics. Our aim is to
provide conservative limits on the tensor-to-scalar ratio for standard
inflationary models. For power-law inflation, for example, we find T/S<0.52 at
95% confidence, with a similar constraint for phi^p potentials. However, for
models with tensor amplitude unrelated to the scalar spectral index it is still
currently possible to have T/S>1.Comment: 23 pages, 7 figures, accepted for publication in Phys. Rev. D.
Calculations extended to blue spectral index, Fig. 6 added, discussion of
results expande
Cosmological parameters from SDSS and WMAP
We measure cosmological parameters using the three-dimensional power spectrum
P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in
combination with WMAP and other data. Our results are consistent with a
``vanilla'' flat adiabatic Lambda-CDM model without tilt (n=1), running tilt,
tensor modes or massive neutrinos. Adding SDSS information more than halves the
WMAP-only error bars on some parameters, tightening 1 sigma constraints on the
Hubble parameter from h~0.74+0.18-0.07 to h~0.70+0.04-0.03, on the matter
density from Omega_m~0.25+/-0.10 to Omega_m~0.30+/-0.04 (1 sigma) and on
neutrino masses from <11 eV to <0.6 eV (95%). SDSS helps even more when
dropping prior assumptions about curvature, neutrinos, tensor modes and the
equation of state. Our results are in substantial agreement with the joint
analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive
consistency check with independent redshift survey data and analysis
techniques. In this paper, we place particular emphasis on clarifying the
physical origin of the constraints, i.e., what we do and do not know when using
different data sets and prior assumptions. For instance, dropping the
assumption that space is perfectly flat, the WMAP-only constraint on the
measured age of the Universe tightens from t0~16.3+2.3-1.8 Gyr to
t0~14.1+1.0-0.9 Gyr by adding SDSS and SN Ia data. Including tensors, running
tilt, neutrino mass and equation of state in the list of free parameters, many
constraints are still quite weak, but future cosmological measurements from
SDSS and other sources should allow these to be substantially tightened.Comment: Minor revisions to match accepted PRD version. SDSS data and ppt
figures available at http://www.hep.upenn.edu/~max/sdsspars.htm
Is cosmology consistent?
We perform a detailed analysis of the latest CMB measurements (including
BOOMERaNG, DASI, Maxima and CBI), both alone and jointly with other
cosmological data sets involving, e.g., galaxy clustering and the Lyman Alpha
Forest. We first address the question of whether the CMB data are internally
consistent once calibration and beam uncertainties are taken into account,
performing a series of statistical tests. With a few minor caveats, our answer
is yes, and we compress all data into a single set of 24 bandpowers with
associated covariance matrix and window functions. We then compute joint
constraints on the 11 parameters of the ``standard'' adiabatic inflationary
cosmological model. Out best fit model passes a series of physical consistency
checks and agrees with essentially all currently available cosmological data.
In addition to sharp constraints on the cosmic matter budget in good agreement
with those of the BOOMERaNG, DASI and Maxima teams, we obtain a heaviest
neutrino mass range 0.04-4.2 eV and the sharpest constraints to date on gravity
waves which (together with preference for a slight red-tilt) favors
``small-field'' inflation models.Comment: Replaced to match accepted PRD version. 14 pages, 12 figs. Tiny
changes due to smaller DASI & Maxima calibration errors. Expanded neutrino
and tensor discussion, added refs, typos fixed. Combined CMB data, window and
covariance matrix at http://www.hep.upenn.edu/~max/consistent.html or from
[email protected]
Same-sex and different-sex parent households and child health outcomes:Findings from the national survey of children's health
Objective: Using the 2011–2012 National Survey of Children's Health data set, we compared spouse/partner relationships and parent-child relationships (family relationships), parenting stress, and children's general health, emotional difficulties, coping behavior, and learning behavior (child outcomes) in households of same-sex (female) versus different-sex continuously coupled parents with biological offspring. We assessed whether associations among family relationships, parenting stress, and child outcomes were different in the 2 household types. Methods: Parental and child characteristics were matched for 95 female same-sex parent and 95 different-sex parent households with children 6 to 17 years old. One parent per household was interviewed by telephone. Multivariate analyses of variance and multiple linear regressions were conducted. Results: No differences were observed between household types on family relationships or any child outcomes. Same-sex parent households scored higher on parenting stress (95% confidence interval = 2.03–2.30) than different-sex parent households (95% confidence interval = 1.76–2.03), p = .006. No significant interactions between household type and family relationships or household type and parenting stress were found for any child outcomes. Conclusion: Children with female same-sex parents and different-sex parents demonstrated no differences in outcomes, despite female same-sex parents reporting more parenting stress. Future studies may reveal the sources of this parenting stress
Planck intermediate results. VIII. Filaments between interacting clusters
About half of the baryons of the Universe are expected to be in the form of
filaments of hot and low density intergalactic medium. Most of these baryons
remain undetected even by the most advanced X-ray observatories which are
limited in sensitivity to the diffuse low density medium. The Planck satellite
has provided hundreds of detections of the hot gas in clusters of galaxies via
the thermal Sunyaev-Zel'dovich (tSZ) effect and is an ideal instrument for
studying extended low density media through the tSZ effect. In this paper we
use the Planck data to search for signatures of a fraction of these missing
baryons between pairs of galaxy clusters. Cluster pairs are good candidates for
searching for the hotter and denser phase of the intergalactic medium (which is
more easily observed through the SZ effect). Using an X-ray catalogue of
clusters and the Planck data, we select physical pairs of clusters as
candidates. Using the Planck data we construct a local map of the tSZ effect
centered on each pair of galaxy clusters. ROSAT data is used to construct X-ray
maps of these pairs. After having modelled and subtracted the tSZ effect and
X-ray emission for each cluster in the pair we study the residuals on both the
SZ and X-ray maps. For the merging cluster pair A399-A401 we observe a
significant tSZ effect signal in the intercluster region beyond the virial
radii of the clusters. A joint X-ray SZ analysis allows us to constrain the
temperature and density of this intercluster medium. We obtain a temperature of
kT = 7.1 +- 0.9, keV (consistent with previous estimates) and a baryon density
of (3.7 +- 0.2)x10^-4, cm^-3. The Planck satellite mission has provided the
first SZ detection of the hot and diffuse intercluster gas.Comment: Accepted by A&
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