11 research outputs found
Detection of virial shocks in stacked Fermi-LAT clusters
In the hierarchical paradigm of structure formation, galaxy clusters are the
largest objects ever to virialize. They are thought to grow by accreting mass
through large scale, strong virial shocks. Such a collisionless shock is
expected to accelerate relativistic electrons, thus generating a spectrally
flat leptonic virial ring. However attempts to detect virial rings have all
failed, leaving the shock paradigm unconfirmed. Here we identify a virial
-ray signal by stacking Fermi-LAT data for 112 clusters, enhancing the
ring sensitivity by rescaling clusters to their virial radii and utilizing the
anticipated spectrum. In addition to a central unresolved, hard signal
(detected at the nominal confidence level), probably dominated by
active galactic nuclei, we identify () a bright, spectrally flat
-ray ring at the expected shock position. It corresponds to (with an uncertainty factor ) thermal energy deposition in
relativistic electrons over a Hubble time. This result validates the shock
paradigm, calibrates its parameters, and indicates that the cumulative emission
from such shocks significantly contributes to the diffuse extragalactic
-ray and radio backgrounds.Comment: Proceedings of the 7th International Fermi Symposium, Garmisch, Oct
15-20 201
A new approach to template banks of gravitational waves with higher harmonics: reducing matched-filtering cost by over an order of magnitude
Searches for gravitational wave events use models, or templates, for the
signals of interest. The templates used in current searches in the
LIGO-Virgo-Kagra (LVK) data model the dominant quadrupole mode
of the signals, and omit sub-dominant higher-order modes (HM) such as
, , which are predicted by general relativity. Hence,
these searches could lose sensitivity to black hole mergers in interesting
parts of parameter space, such as systems with high-masses and asymmetric mass
ratios. We develop a new strategy to include HM in template banks that exploits
the natural connection between the modes. We use a combination of
post-Newtonian formulae and machine learning tools to model aligned-spin
, waveforms corresponding to a given waveform. Each of
these modes can be individually filtered against the data to yield separate
timeseries of signal-to-noise ratios (SNR), which can be combined in a
relatively inexpensive way to marginalize over extrinsic parameters of the
signals. This leads to a HM search pipeline whose matched-filtering cost is
just that of a quadrupole-only search (in contrast to being
, as in previously proposed HM search methods). Our
method is effectual and is generally applicable for template banks constructed
with either stochastic or geometric placement techniques. Additionally, we
discuss compression of -only geometric-placement template banks using
machine learning algorithms.Comment: 12+2 pages, 7+1 figures. The template bank described here will be
publicly available at
https://github.com/JayWadekar/GW_higher_harmonics_searc
New binary black hole mergers in the LIGO-Virgo O3b data
We report the detection of 5 new candidate binary black hole (BBH) merger
signals in the publicly released data from the second half of the third
observing run (O3b) of advanced LIGO and advanced Virgo. The LIGO-Virgo-KAGRA
(LVK) collaboration reported 35 compact binary coalescences (CBCs) in their
analysis of the O3b data [1], with 30 BBH mergers having coincidence in the
Hanford and Livingston detectors. We confirm 17 of these for a total of 22
detections in our analysis of the Hanford-Livingston coincident O3b data. We
identify candidates using a search pipeline employing aligned-spin
quadrupole-only waveforms. Our pipeline is similar to the one used in our O3a
coincident analysis [2], except for a few improvements in the veto procedure
and the ranking statistic, and we continue to use an astrophysical probability
of one half as our detection threshold, following the approach of the LVK
catalogs. Most of the new candidates reported in this work are placed in the
upper and lower-mass gap of the black hole (BH) mass distribution. One BBH
event also shows a sign of spin-orbit precession with negatively aligned spins.
We also identify a possible neutron star-black hole (NSBH) merger. We expect
these events to help inform the black hole mass and spin distributions inferred
in a full population analysis.Comment: 16 pages, 12 figure
Estimating the returns to UK publicly funded cancer-related research in terms of the net value of improved health outcomes
© 2014 Glover et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Background - Building on an approach developed to assess the economic returns to cardiovascular research, we estimated the economic returns from UK public and charitable funded cancer-related research that arise from the net value of the improved health outcomes.
Methods - To assess these economic returns from cancer-related research in the UK we estimated: 1) public and charitable expenditure on cancer-related research in the UK from 1970 to 2009; 2) net monetary benefit (NMB), that is, the health benefit measured in quality adjusted life years (QALYs) valued in monetary terms (using a base-case value of a QALY of GB£25,000) minus the cost of delivering that benefit, for a prioritised list of interventions from 1991 to 2010; 3) the proportion of NMB attributable to UK research; 4) the elapsed time between research funding and health gain; and 5) the internal rate of return (IRR) from cancer-related research investments on health benefits. We analysed the uncertainties in the IRR estimate using sensitivity analyses to illustrate the effect of some key parameters.
Results - In 2011/12 prices, total expenditure on cancer-related research from 1970 to 2009 was £15 billion. The NMB of the 5.9 million QALYs gained from the prioritised interventions from 1991 to 2010 was £124 billion. Calculation of the IRR incorporated an estimated elapsed time of 15 years. We related 17% of the annual NMB estimated to be attributable to UK research (for each of the 20 years 1991 to 2010) to 20 years of research investment 15 years earlier (that is, for 1976 to 1995). This produced a best-estimate IRR of 10%, compared with 9% previously estimated for cardiovascular disease research. The sensitivity analysis demonstrated the importance of smoking reduction as a major source of improved cancer-related health outcomes.
Conclusions - We have demonstrated a substantive IRR from net health gain to public and charitable funding of cancer-related research in the UK, and further validated the approach that we originally used in assessing the returns from cardiovascular research. In doing so, we have highlighted a number of weaknesses and key assumptions that need strengthening in further investigations. Nevertheless, these cautious estimates demonstrate that the returns from past cancer research have been substantial, and justify the investments made during the period 1976 to 1995.Wellcome Trust, Cancer
Research UK, the National Institute of Health Research, and the Academy of
Medical Sciences
Removing degeneracy and multimodality in gravitational wave source parameters
Quasicircular binary black hole mergers are described by 15 parameters, of
which gravitational wave observations can typically constrain only
independent combinations to varying degree. In this work, we devise coordinates
that remove correlations, and disentangle well- and poorly-measured quantities.
Additionally, we identify approximate discrete symmetries in the posterior as
the primary cause of multimodality, and design a method to tackle this type of
multimodality. The resulting posteriors have little structure and can be
sampled efficiently and robustly. We provide a Python package for parameter
estimation, cogwheel, that implements these methods together with other
algorithms for accelerating the inference process. One of the coordinates we
introduce is a spin azimuth that can be measured remarkably well in the
presence of orbital precession, and we anticipate that this will shed light on
the occurrence of spin-orbit misalignment in nature.Comment: 16 pages, 13 figures, 1 tabl