345 research outputs found
Towards understanding the Planck thermal dust models
Understanding the properties of dust emission in the microwave domain is an
important premise for the next generation of cosmic microwave background (CMB)
experiments, devoted to the measurement of the primordial -modes of
polarization. In this paper, we compare three solutions to thermal dust
emission by the Planck Collaboration \cite{PlanckDust03,planck_16,planck_com}
to point out significant differences between their respective parameters (the
spectral index , the optical depth and the dust temperature
). These differences originate from e.g. the priors on the parameters or
the contribution of the Cosmic infrared background (CIB).Comment: 7 pages, 8 figures, Accepted for publication in PR
Statistical properties of polarized CMB foreground maps
Foreground removal techniques for CMB analyses make specific assumptions
about the properties of foregrounds in temperature and in polarization. By
investigating the statistics of foreground components more understanding about
the degree to which these assumptions are valid can be obtained. In this work
we investigate - and -mode maps of the two strongest polarized
foregrounds, synchrotron and thermal dust emission, with regards to their
similarity with Gaussian processes, their spectral variations and
cross-correlations. We perform tests in patches of size
collectively covering the full sky and find most of them to conform with their
Gaussian expectation according to the statistics in use. Correlations exhibit
distinct differences in - and -mode signals which point towards
necessities in foreground removal methods. We discuss potential consequences
and possible further directions.Comment: 10 pages, 9 figures. v3: Complementary results added, esp. in
Appendix. Accepted by MNRA
From top-hat masking to smooth transitions: P-filter and its application to polarized microwave sky maps
In CMB science, the simplest idea to remove a contaminated sky region is to
multiply the sky map with a mask that is 0 for the contaminated region and 1
elsewhere, which is also called a top-hat masking. Although it is easy to use,
such top-hat masking is known to suffer from various leakage problems.
Therefore, we want to extend the top-hat masking to a series of semi-analytic
functions called the P-filters. Most importantly, the P-filters can seamlessly
realize the core idea of masking in CMB science, and, meanwhile, guarantee
continuity up to the first derivative everywhere. The P-filters can
significantly reduce many leakage problems without additional cost, including
the leakages due to low-, high-, and band-pass filtering, and the E-to-E,
B-to-B, B-to-E, and E-to-B leakages. The workings of the P-filter are
illustrated by using the WMAP and Planck polarization sky maps. By comparison
to the corresponding WMAP/Planck masks, we show that the P-filter performs much
better than top-hat masking, and meanwhile, has the potential to supersede the
principal idea of masking in CMB science. Compared to mask apodization, the
P-filter is ``outward'', that tends to make proper use of the region that was
marked as 0; whereas apodization is ``inward'', that always kills more signal
in the region marked as 1.Comment: 19 pages and 11 figure
Skewness and Kurtosis as Indicators of Non-Gaussianity in Galactic Foreground Maps
Observational cosmology is entering an era in which high precision will be
required in both measurement and data analysis. Accuracy, however, can only be
achieved with a thorough understanding of potential sources of contamination
from foreground effects. Our primary focus will be on non- Gaussian effects in
foregrounds. This issue will be crucial for coming experiments to determine
B-mode polarization. We propose a novel method for investigating a data set in
terms of skewness and kurtosis in locally defined regions that collectively
cover the entire sky. The method is demonstrated on two sky maps: (i) the SMICA
map of Cosmic Microwave Background fluctuations provided by the Planck
Collaboration and (ii) a version of the Haslam map at 408 MHz that describes
synchrotron radiation. We find that skewness and kurtosis can be evaluated in
combination to reveal local physical information. In the present case, we
demonstrate that the local properties of both maps are predominantly Gaussian.
This result was expected for the SMICA map; that it also applies for the Haslam
map is surprising. The approach described here has a generality and flexibility
that should make it useful in a variety of astrophysical and cosmological
contexts.Comment: 15 pages, 7 figures, minor change, as published in JCA
On the time lags of the LIGO signals
To date, the LIGO collaboration has detected three gravitational wave (GW)
events appearing in both its Hanford and Livingston detectors. In this article
we reexamine the LIGO data with regard to correlations between the two
detectors. With special focus on GW150914, we report correlations in the
detector noise which, at the time of the event, happen to be maximized for the
same time lag as that found for the event itself. Specifically, we analyze
correlations in the calibration lines in the vicinity of 35\,Hz as well as the
residual noise in the data after subtraction of the best-fit theoretical
templates. The residual noise for the other two events, GW151226 and GW170104,
exhibits similar behavior. A clear distinction between signal and noise
therefore remains to be established in order to determine the contribution of
gravitational waves to the detected signals.Comment: The body of the current version is essentially identical to the
previous one submitted to arxiv and JCAP. In order to meet the various
suggestions of the referees, we have included an extended and detailed
Appendix. This Appendix also contains significant new results that provide
additional support for our conclusions. This version of our manuscript has
been accepted for publication by JCA
The Morphology of the Anomalous Microwave Emission in the Planck 2015 data release
We calculate weighted mosaic correlations between the recently published
Planck 2015 foreground maps - both anomalous microwave emission (AME) maps,
free-free emission, synchrotron radiation and thermal dust emission. The
weighting coefficients are constructed taking account of the signal-to-error
ratio given by the data product. Positive correlation is found for AME compared
with thermal dust emission as well as synchrotron radiation. We find AME and
free-free emission tending to be anti-correlated, however, when investigating
different scales, their relationship appears to be more complex. We argue that
dust particles responsible for AME are pushed out of hot zones in the
interstellar medium (ISM)
Degeneracy of gravitational waveforms in the context of GW150914
We study the degeneracy of theoretical gravitational waveforms for binary
black hole mergers using an aligned-spin effective-one-body model. After
appropriate truncation, bandpassing, and matching, we identify regions in the
mass--spin parameter space containing waveforms similar to the template
proposed for GW150914, with masses and , using the cross-correlation coefficient as a measure of
the similarity between waveforms. Remarkably high cross-correlations are found
across broad regions of parameter space. The associated uncertanties exceed
these from LIGO's Bayesian analysis considerably. We have shown that waveforms
with greatly increased masses, such as and , and strong anti-aligned spins ( and )
yield almost the same signal-to-noise ratio in the strain data for GW150914.Comment: Accepted for publication in JCA
Evaluating Federally Appointed Judges in Canada: Analyzing the Controversy
This commentary describes our experiences in trying to undertake a judicial performance evaluation of federally appointed judges in Canada. Some respondents were enthusiastic about the project, but others were strongly opposed to it and worried about the effects that our survey would have on judicial independence. After describing the feedback that we received and the fallout from our project, we examine the relationship between judicial performance evaluation and judicial independence. We argue that a well-conceived judicial performance evaluation does not violate judicial independence. We then explore the resistance to judicial performance evaluation in Canada, using a comparative lens. The explanation for this opposition, it seems, lies partly in the broader socio-political context found in common law jurisdictions with parliamentary systems of government and no judicial elections. In our view, opposition to outside academic inquiry from strong elements within the Canadian legal community also forms part of the answer
Does Patronage Matter? Connecting Influences on Judicial Appointments with Judicial Decision Making
The federal government\u27s power to appoint judges has come under increased scrutiny in recent years. While many suggest that partisan affiliation, gender and professional background may be influencing the Canadian appointment process, and some have called into question the fairness of such influences, little attention has been directed at determining whether these characteristics influence the outcome of cases. This paper studies decisions made by the Ontario Court of Appeal between 1990 and 2003 and uses a unique measure of partisan affiliation in an attempt to answer the question: do characteristics which play a role in the appointment process influence judicial decision makin
Exploring the Links Between Party and Appointment: Canadian Federal Judicial Appointments from 1989 to 2003
Studies of federal judicial appointments made before 1988 discovered significant partisan ties between judicial appointees and the governments appointing them. In 1988, in response to criticism of these “patronage appointments,” the Mulroney government introduced screening committees to the process. This article explores the impact of these committees. Using information gained from surveys of legal elites, we trace the minor and major political connections of federal judicial appointees from 1989 to 2003 in order to determine whether patronage has continued despite the reform to the process. We discover that political connections continued to play an important role in who was selected for a judicial appointment. However, these connections were not quite as common as those found before 1988, and the new process does appear to have prevented the politically motivated appointment of completely unqualified candidates. Interestingly, our findings also suggest that the impact of patronage varies by region and interacts with other, newer influences, in particular, concerns for group representation on the bench. The paper concludes by briefly discussing these results in the context of the relationship between judicial selection and politics with a comparative perspective
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