668 research outputs found
MASTER of the CMB Anisotropy Power Spectrum: A Fast Method for Statistical Analysis of Large and Complex CMB Data Sets
We describe a fast and accurate method for estimation of the cosmic microwave
background (CMB) anisotropy angular power spectrum --- Monte Carlo Apodised
Spherical Transform EstimatoR. Originally devised for use in the interpretation
of the Boomerang experimental data, MASTER is both a computationally efficient
method suitable for use with the currently available CMB data sets (already
large in size, despite covering small fractions of the sky, and affected by
inhomogeneous and correlated noise), and a very promising application for the
analysis of very large future CMB satellite mission products.Comment: 20 pages, 6 fig; submitted to ApJ; uses aastex.cls and psfig.sty
(included
The Cosmic Microwave Background & Inflation, Then & Now
Boomerang, Maxima, DASI, CBI and VSA significantly increase the case for
accelerated expansion in the early universe (the inflationary paradigm) and at
the current epoch (dark energy dominance), especially when combined with data
on high redshift supernovae (SN1) and large scale structure (LSS). There are
``7 pillars of Inflation'' that can be shown with the CMB probe, and at least
5, and possibly 6, of these have already been demonstrated in the CMB data: (1)
a large scale gravitational potential; (2) acoustic peaks/dips; (3) damping due
to shear viscosity; (4) a Gaussian (maximally random) distribution; (5)
secondary anisotropies; (6) polarization. A 7th pillar, anisotropies induced by
gravity wave quantum noise, could be too small. A minimal inflation parameter
set, \omega_b,\omega_{cdm}, \Omega_{tot}, \Omega_Q,w_Q,n_s,\tau_C, \sigma_8},
is used to illustrate the power of the current data. We find the CMB+LSS+SN1
data give \Omega_{tot} =1.00^{+.07}_{-.03}, consistent with (non-baroque)
inflation theory. Restricting to \Omega_{tot}=1, we find a nearly scale
invariant spectrum, n_s =0.97^{+.08}_{-.05}. The CDM density, \Omega_{cdm}{\rm
h}^2 =.12^{+.01}_{-.01}, and baryon density, \Omega_b {\rm h}^2 =
>.022^{+.003}_{-.002}, are in the expected range. (The Big Bang nucleosynthesis
estimate is 0.019\pm 0.002.) Substantial dark (unclustered) energy is inferred,
\Omega_Q \approx 0.68 \pm 0.05, and CMB+LSS \Omega_Q values are compatible with
the independent SN1 estimates. The dark energy equation of state, crudely
parameterized by a quintessence-field pressure-to-density ratio w_Q, is not
well determined by CMB+LSS (w_Q < -0.4 at 95% CL), but when combined with SN1
the resulting w_Q < -0.7 limit is quite consistent with the w_Q=-1 cosmological
constant case.Comment: 20 pages, 8 figures, in Theoretical Physics, MRST 2002: A Tribute to
George Libbrandt (AIP), eds. V. Elias, R. Epp, R. Myer
Statistical Properties of Galactic Starlight Polarization
We present a statistical analysis of Galactic interstellar polarization from
the largest compilation available of starlight data. The data comprises ~ 9300
stars of which we have selected ~ 5500 for our analysis. We find a nearly
linear growth of mean polarization degree with extinction. The amplitude of
this correlation shows that interstellar grains are not fully aligned with the
Galactic magnetic field, which can be interpreted as the effect of a large
random component of the field. In agreement with earlier studies of more
limited scope, we estimate the ratio of the uniform to the random
plane-of-the-sky components of the magnetic field to be B_u/B_r = 0.8.
Moreover, a clear correlation exists between polarization degree and
polarization angle what provides evidence that the magnetic field geometry
follows Galactic structures on large-scales. The angular power spectrum C_l of
the starlight polarization degree for Galactic plane data (|b| < 10 deg) is
consistent with a power-law, C_l ~ l^{-1.5} (where l ~ 180 deg/\theta is the
multipole order), for all angular scales \theta > 10 arcmin. An investigation
of sparse and inhomogeneous sampling of the data shows that the starlight data
analyzed traces an underlying polarized continuum that has the same power
spectrum slope, C_l ~ l^{-1.5}. Our findings suggest that starlight data can be
safely used for the modeling of Galactic polarized continuum emission at other
wavelengths.Comment: 31 pages, 11 figures. Minor corrections and some clarifications
included. Matches version accepted for publication by the Astrophysical
Journa
Interstellar dust in the BOOMERanG maps
Interstellar dust (ISD) emission is present in the mm-wave maps obtained by the BOOMERanG experiment at intermediate and high Galactic latitudes. We find that, while being sub-dominant at the lower frequencies (90,150, 240 GHz), thermal emission from ISD is dominant at 410 GHz, and is well correlated with the IRAS map at 100 Āµm. We find also that the angular power spectrum of ISD fluctuations at 410 GHz is a power law, and its level is negligible with respect to the angular power spectrum of the Cosmic Microwave Background (CMB) at 90 and 150 GHz
A formal verification framework and associated tools for enterprise modeling : application to UEML
The aim of this paper is to propose and apply a verification and validation approach to Enterprise Modeling that enables the user to improve the relevance and correctness, the suitability and coherence of a model by using properties specification and formal proof of properties
Foregrounds in the BOOMERANG-LDB data: a preliminary rms analysis
We present a preliminary analysis of the BOOMERanG LDB maps, focused on
foregrounds. BOOMERanG detects dust emission at moderately low galactic
latitudes () in bands centered at 90, 150, 240, 410 GHz. At higher
Galactic latitudes, we use the BOOMERanG data to set conservative upper limits
on the level of contamination at 90 and 150 GHz. We find that the mean square
signal correlated with the IRAS/DIRBE dust template is less than 3% of the mean
square signal due to CMB anisotropy
Measuring CMB polarisation with the Planck mission
In this paper, we discuss why and how the Planck mission, originally designed
and proposed for mapping CMB intensity fluctuations, has been revised for
polarisation measurement capability as well
The Sunyaev-Zeldovich effect in CMB-calibrated theories applied to the Cosmic Background Imager anisotropy power at l > 2000
We discuss the nature of the possible high-l excess in the Cosmic Microwave
Background (CMB) anisotropy power spectrum observed by the Cosmic Background
Imager (CBI). We probe the angular structure of the excess in the CBI deep
fields and investigate whether it could be due to the scattering of CMB photons
by hot electrons within clusters, the Sunyaev-Zeldovich (SZ) effect. We
estimate the density fluctuation parameters for amplitude, sigma_8, and shape,
Gamma, from CMB primary anisotropy data and other cosmological data. We use the
results of two separate hydrodynamical codes for Lambda-CDM cosmologies,
consistent with the allowed sigma_8 and Gamma values, to quantify the expected
contribution from the SZ effect to the bandpowers of the CBI experiment and
pass simulated SZ effect maps through our CBI analysis pipeline. The result is
very sensitive to the value of sigma_8, and is roughly consistent with the
observed power if sigma_8 ~ 1. We conclude that the CBI anomaly could be a
result of the SZ effect for the class of Lambda-CDM concordance models if
sigma_8 is in the upper range of values allowed by current CMB and Large Scale
Structure (LSS) data.Comment: Accepted by The Astrophysical Journal; 17 pages including 12 color
figures. v2 matches accepted version. Additional information at
http://www.astro.caltech.edu/~tjp/CBI
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