134 research outputs found
A comparison of CMB Angular Power Spectrum Estimators at Large Scales: the TT case
In the context of cosmic microwave background (CMB) data analysis, we compare
the efficiency at large scale of two angular power spectrum algorithms,
implementing, respectively, the quadratic maximum likelihood (QML) estimator
and the pseudo spectrum (pseudo-Cl) estimator. By exploiting 1000 realistic
Monte Carlo (MC) simulations, we find that the QML approach is markedly
superior in the range l=[2-100]. At the largest angular scales, e.g. l < 10,
the variance of the QML is almost 1/3 (1/2) that of the pseudo-Cl, when we
consider the WMAP kq85 (kq85 enlarged by 8 degrees) mask, making the pseudo
spectrum estimator a very poor option. Even at multipoles l=[20-60], where
pseudo-Cl methods are traditionally used to feed the CMB likelihood algorithms,
we find an efficiency loss of about 20%, when we considered the WMAP kq85 mask,
and of about 15% for the kq85 mask enlarged by 8 degrees. This should be taken
into account when claiming accurate results based on pseudo-Cl methods. Some
examples concerning typical large scale estimators are provided.Comment: 9 pages, 7 figures. Accepted for publication in MNRA
On the impact of large angle CMB polarization data on cosmological parameters
(abridged) We study the impact of the large-angle CMB polarization datasets
publicly released by the WMAP and Planck satellites on the estimation of
cosmological parameters of the CDM model. To complement large-angle
polarization, we consider the high-resolution CMB datasets from either WMAP or
Planck, as well as CMB lensing as traced by Planck. In the case of WMAP, we
compute the large-angle polarization likelihood starting over from
low-resolution frequency maps and their covariance matrices, and perform our
own foreground mitigation technique, which includes as a possible alternative
Planck 353 GHz data to trace polarized dust. We find that the latter choice
induces a downward shift in the optical depth , of order ~,
robust to the choice of the complementary high-l dataset. When the Planck 353
GHz is consistently used to minimize polarized dust emission, WMAP and Planck
70 GHz large-angle polarization data are in remarkable agreement: by combining
them we find , again very stable against the
particular choice for high- data. We find that the amplitude of
primordial fluctuations , notoriously degenerate with , is the
parameter second most affected by the assumptions on polarized dust removal,
but the other parameters are also affected, typically between and
. In particular, cleaning dust with \planck's 353 GHz data imposes a
downward shift in the value of the Hubble constant ,
significantly contributing to the tension reported between CMB based and direct
measurements of . On the other hand, we find that the appearance of the
so-called low anomaly, a well-known tension between the high- and
low-resolution CMB anisotropy amplitude, is not significantly affected by the
details of large-angle polarization, or by the particular high- dataset
employed.Comment: 19 pages, 4 figures, 3 table
CMB Polarization Systematics, Cosmological Birefringence and the Gravitational Waves Background
Cosmic Microwave Background experiments must achieve very accurate
calibration of their polarization reference frame to avoid biasing the
cosmological parameters. In particular, a wrong or inaccurate calibration might
mimic the presence of a gravitational wave background, or a signal from
cosmological birefringence, a phenomenon characteristic of several
non-standard, symmetry breaking theories of electrodynamics that allow for
\textit{in vacuo} rotation if the polarization direction of the photon.
Noteworthly, several authors have claimed that the BOOMERanG 2003 (B2K)
published polarized power spectra of the CMB may hint at cosmological
birefringence. Such analyses, however, do not take into account the reported
calibration uncertainties of the BOOMERanG focal plane. We develop a formalism
to include this effect and apply it to the BOOMERanG dataset, finding a
cosmological rotation angle . We also
investigate the expected performances of future space borne experiment, finding
that an overall miscalibration larger then for Planck and
for EPIC, if not properly taken into account, will produce a bias on the
constraints on the cosmological parameters and could misleadingly suggest the
presence of a GW background.Comment: 10 pages, 3 figure
Using CMB data to constrain non-isotropic Planck-scale modifications to Electrodynamics
We develop a method to constrain non-isotropic features of Cosmic Microwave
Background (CMB) polarization, of a type expected to arise in some models
describing quantum gravity effects on light propagation. We describe the
expected signatures of this kind of anomalous light propagation on CMB photons,
showing that it will produce a non-isotropic birefringence effect, i.e. a
rotation of the CMB polarization direction whose observed amount depends in a
peculiar way on the observation direction. We also show that the sensitivity
levels expected for CMB polarization studies by the \emph{Planck} satellite are
sufficient for testing these effects if, as assumed in the quantum-gravity
literature, their magnitude is set by the minute Planck length.Comment: 18 pages, 4 figures, 2 table
Images of the Early Universe from the BOOMERanG experiment
The CMB is the fundamental tool to study the properties of the early universe and of the
universe at large scales. In the framework of the Hot Big Bang model, when we look to
the CMB we look back in time to the end of the plasma era, at a redshift ~ 1000, when
the universe was ~ 50000 times younger, ~ 1000 times hotter and ~ 10^9 times denser
than today. The image of the CMB can be used to study the physical processes there, to
infer what happened before, and also to study the background geometry of our Universe
â-space spectroscopy of the Cosmic Microwave Background with the BOOMERanG experiment
The BOOMERanG experiment has recently produced detailed maps of the Cosmic Microwave Background, where sub-horizon structures are resolved with good signal to noise ratio. A power spectrum (spherical harmonics) analysis of the maps detects three peaks, at multipoles â = (213_(-13)^(+10)),(541_(-32)^(+20))(845_(-25)^(+12)). In this paper we discuss the data analysis and the implications of these results for cosmology
The Gamma-Flash data acquisition system for observation of terrestrial gamma-ray flashes
Gamma-Flash is an Italian project funded by the Italian Space Agency (ASI)
and led by the National Institute for Astrophysics (INAF), devoted to the
observation and study of high-energy phenomena, such as terrestrial gamma-ray
flashes and gamma-ray glows produced in the Earth's atmosphere during
thunderstorms. The project's detectors and the data acquisition and control
system (DACS) are placed at the "O. Vittori" observatory on the top of Mt.
Cimone (Italy). Another payload will be placed on an aircraft for observations
of thunderstorms in the air. This work presents the architecture of the data
acquisition and control system and the data flow.Comment: 4 pages, 1 figure, Astronomical Data Analysis Software and System
XXXII (2022
The Euclid Science Ground Segment Distributed Infrastructure: System Integration and Challenges
The Science Ground Segment (SGS) of the Euclid mission provides distributed and redundant data storage and processing, federating nine Science Data Centres (SDCs) and a Science Operations Centre. The SGS reference architecture is based on loosely coupled systems and services, broadly organized into a common infrastructure of transverse software components and the scientific data Processing Functions. The SGS common infrastructure includes: 1) the Euclid Archive System (EAS), a central metadata repository which inventories, indexes and localizes the huge amount of distributed data; 2) a Distributed Storage System of EAS, providing a unified view of the SDCs storage systems and supporting several transfer protocols; 3) an Infrastructure Abstraction Layer, isolating the scientific data processing software from the underlying IT infrastructure and providing a common, lightweight workflow management system; 4) a Common Orchestration System, performing a balanced distribution of data and processing among the SDCs. Virtualization is another key element of the SGS infrastructure. We present the status of the Euclid SGS software infrastructure, the prototypes developed and the continuous system integration and testing performed through the Euclid âSGS Challengesâ
CAESAR: Space Weather archive prototype for ASPIS
The project CAESAR (Comprehensive spAce wEather Studies for the ASPIS
prototype Realization) is aimed to tackle all the relevant aspects of Space
Weather (SWE) and realize the prototype of the scientific data centre for Space
Weather of the Italian Space Agency (ASI) called ASPIS (ASI SPace Weather
InfraStructure). This contribution is meant to bring attention upon the first
steps in the development of the CAESAR prototype for ASPIS and will focus on
the activities of the Node 2000 of CAESAR, the set of Work Packages dedicated
to the technical design and implementation of the CAESAR ASPIS archive
prototype. The product specifications of the intended resources that will form
the archive, functional and system requirements gathered as first steps to seed
the design of the prototype infrastructure, and evaluation of existing
frameworks, tools and standards, will be presented as well as the status of the
project in its initial stage.Comment: 4 pages, 2 figures, ADASS XXXII (2022) Proceeding
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