188 research outputs found
Overview of MHz air shower radio experiments and results
In this paper, I present a review of the main results obtained in the last 10
years in the field of radio-detection of cosmic-ray air showers in the MHz
range. All results from all experiments cannot be reported here so that I will
focus on the results more than on the experiments themselves. Modern
experiments started in 2003 with CODALEMA and LOPES. In 2006, small-size
autonomous prototypes setup were installed at the Pierre Auger Observatory
site, to help the design of the Auger Engineering Radio Array (AERA). We will
discuss the principal aspects of the radio data analysis and the determination
of the primary cosmic ray characteristics: the arrival direction, the lateral
distribution of the electric field, the correlation with the primary energy,
the emission mechanisms and the sensitivity to the composition of the cosmic
rays.Comment: Proceedings of the ARENA2012 conference (Erlangen, Germany), to be
published in AIP Conference Proceeding
Radio emission from the air shower sudden death
We present a new mechanism for air shower radio emission due to the sudden
absorption of secondary particles when the shower front hits the ground. The
electrons present in excess during the air shower development imply a net
residual negative charge in the shower front. We show that for showers hitting
the ground before the complete extinction of their electromagnetic component,
the sudden vanishing of the net residual negative charge generates an electric
field contribution in the kHz---MHz range. We characterize this radio
contribution as a function of primary energy, arrival direction and antenna
position, using the simulation code SELFAS2. We discuss the interest of this
new predicted signal on detection and analysis of ultra-high energy cosmic-rays
and we argue that the region in the shower of maximum emission of the electric
field should not coincide with the region of maximum development.Comment: 8 pages, 15 figures, Submitted to Astroparticle Physics on October 6,
201
Scanning strategy for mapping the Cosmic Microwave Background anisotropies with Planck
We present simulations of different scanning strategies for the Planck
satellite. We review the properties of slow- and fast-precession strategies in
terms of uniformity of the integration time on the sky, the presence of
low-redundancy areas, the presence of deep fields, the presence of sharp
gradients in the integration time, and the redundancy of the scanning
directions. We also compare the results obtained when co-adding all detectors
of a given frequency channel. The slow-precession strategies allow a good
uniformity of the coverage, while providing two deep fields. On the other hand,
they do not allow a wide spread of the scan-crossing directions, which is a
feature of the fast-precession strategies. However, the latter suffer from many
sharp gradients and low-coverage areas on the sky. On the basis of these
results, the strategy for Planck can be selected to be a slow (e.g. 4
month-period) sinusoidal or cycloidal scanning.Comment: 10 pages, 12 figures, accepted in A&A. Degraded JPEG figure
Simulation of radio emission from cosmic ray air shower with SELFAS2
We present a microscopic computation of the radio emission from air showers
initiated by ultra-high energy cosmic rays in the atmosphere. The strategy
adopted is to compute each secondary particle contribution of the
electromagnetic component and to construct the total signal at any location.
SELFAS2 is a code which doesn't rely on air shower generators like AIRES or
CORSIKA and it is based on the concept of air shower universality which makes
it completely autonomous. Each positron and electron of the air shower is
generated randomly following relevant distributions and tracking them along
their travel in the atmosphere. We confirm in this paper earlier results that
the radio emission is mainly due to the time derivative of the transverse
current and the time derivative of the charge excess. The time derivative of
the transverse current created by systematic deviations of charges in the
geomagnetic field is usually dominant compared to the charge excess
contribution except for the case of an air shower parallel to the geomagnetic
field.Comment: 17 pages, 21 figure
On the wavelet analysis of CMB time ordered data: application to Archeops
We present an alternative analysis of CMB time ordered data (TOD) using a
wavelet-based representation of the data time-frequency plane. We demonstrate
that the wavelet transform decorrelates -type Gaussian stationary noise
and permits a simple and functional description of locally stationary
processes. In particular, this makes possible the generalization of the
classical algorithms of map making and CMB power spectrum estimation to the
case of locally stationary 1/f type noise. As an example, we present a wavelet
based algorithm for the destriping of CMB-like maps. In addition, we describe a
wavelet-based analysis of the Archeops data including time-frequency
visualization, wavelet destriping and filtering of the TOD. These filtered data
was used to produce polarized maps of Galactic dust diffuse emission. Finally,
we describe the modeling of the non-stationarity on the Archeops noise for the
estimation of the CMB power spectrum.Comment: submitted to A & A Figures in jpg format For a full postscript vesion
of the paper, please contact the author
Joint cosmological and gravitational-wave population inference using dark sirens and galaxy catalogues
In the absence of numerous gravitational-wave detections with confirmed
electromagnetic counterparts, the "dark siren" method has emerged as a leading
technique of gravitational-wave cosmology. The method allows redshift
information of such events to be inferred statistically from a catalogue of
potential host galaxies. Due to selection effects, dark siren analyses
necessarily depend on the mass distribution of compact objects and the
evolution of their merger rate with redshift. Informative priors on these
quantities will impact the inferred posterior constraints on the Hubble
constant (). It is thus crucial to vary these unknown distributions during
an inference. This was not possible in earlier analyses due to the high
computational cost, restricting them to either excluding galaxy catalogue
information, or fixing the gravitational-wave population mass distribution and
risking introducing bias to the measurement. This paper introduces a
significantly enhanced version of the Python package GWCOSMO, which allows
joint estimation of cosmological and compact binary population parameters. This
thereby ensures the analysis is now robust to a major source of potential bias.
The gravitational-wave events from the Third Gravitational-Wave Transient
Catalogue are reanalysed with the GLADE+ galaxy catalogue, and an updated, more
reliable measurement of km s Mpc is found
(maximum a posteriori probability and 68% highest density interval). This
improved method will enable cosmological analyses with future
gravitational-wave detections to make full use of the information available
(both from galaxy catalogues and the compact binary population itself), leading
to promising new independent bounds on the Hubble constant.Comment: 30 pages, 11 figure
Ultimate precision in cosmic-ray radio detection - The SKA
As of 2023, the low-frequency part of the Square Kilometre Array will go online in Australia. It will constitute the largest and most powerful low-frequency radio-astronomical observatory to date, and will facilitate a rich science programme in astronomy and astrophysics. With modest engineering changes, it will also be able to measure cosmic rays via the radio emission from extensive air showers. The extreme antenna density and the homogeneous coverage provided by more than 60,000 antennas within an area of one km 2 will push radio detection of cosmic rays in the energy range around 10 17 eV to ultimate precision, with superior capabilities in the reconstruction of arrival direction, energy, and an expected depth-of-shower-maximum resolution of < 10 g/cm 2
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
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