484 research outputs found
Constraining Lorentz violation with cosmology
The Einstein-Aether theory provides a simple, dynamical mechanism for
breaking Lorentz invariance. It does so within a generally covariant context
and may emerge from quantum effects in more fundamental theories. The theory
leads to a preferred frame and can have distinct experimental signatures. In
this letter, we perform a comprehensive study of the cosmological effects of
the Einstein-Aether theory and use observational data to constrain it. Allied
to previously determined consistency and experimental constraints, we find that
an Einstein-Aether universe can fit experimental data over a wide range of its
parameter space, but requires a specific rescaling of the other cosmological
densities.Comment: 4 pages, 4 figure
Weak gravitational lensing with the Square Kilometre Array
We investigate the capabilities of various stages of the SKA to perform
world-leading weak gravitational lensing surveys. We outline a way forward to
develop the tools needed for pursuing weak lensing in the radio band. We
identify the key analysis challenges and the key pathfinder experiments that
will allow us to address them in the run up to the SKA. We identify and
summarize the unique and potentially very powerful aspects of radio weak
lensing surveys, facilitated by the SKA, that can solve major challenges in the
field of weak lensing. These include the use of polarization and rotational
velocity information to control intrinsic alignments, and the new area of weak
lensing using intensity mapping experiments. We show how the SKA lensing
surveys will both complement and enhance corresponding efforts in the optical
wavebands through cross-correlation techniques and by way of extending the
reach of weak lensing to high redshift.Comment: 19 pages, 6 figures. Cosmology Chapter, Advancing Astrophysics with
the SKA (AASKA14) Conference, Giardini Naxos (Italy), June 9th-13th 201
MAXIPOL: Cosmic Microwave Background Polarimetry Using a Rotating Half-Wave Plate
We discuss MAXIPOL, a bolometric balloon-borne experiment designed to measure
the E-mode polarization of the cosmic microwave background radiation (CMB).
MAXIPOL is the first bolometric CMB experiment to observe the sky using rapid
polarization modulation. To build MAXIPOL, the CMB temperature anisotropy
experiment MAXIMA was retrofitted with a rotating half-wave plate and a
stationary analyzer. We describe the instrument, the observations, the
calibration and the reduction of data collected with twelve polarimeters
operating at 140 GHz and with a FWHM beam size of 10 arcmin. We present maps of
the Q and U Stokes parameters of an 8 deg^2 region of the sky near the star
Beta Ursae Minoris. The power spectra computed from these maps give weak
evidence for an EE signal. The maximum-likelihood amplitude of
l(l+1)C^{EE}_{l}/(2 pi) is 55_{-45}^{+51} uK^2 (68%), and the likelihood
function is asymmetric and skewed positive such that with a uniform prior the
probability that the amplitude is positive is 96%. This result is consistent
with the expected concordance LCDM amplitude of 14 uK^2. The maximum likelihood
amplitudes for l(l+1)C^{BB}_{l}/(2 pi) and are
-31_{-19}^{+31} and 18_{-34}^{+27} uK^2 (68%), respectively, which are
consistent with zero. All of the results are for one bin in the range 151 < l <
693. Tests revealed no residual systematic errors in the time or map domain. A
comprehensive discussion of the analysis of the data is presented in a
companion paper.Comment: 19 pages, 11 figures, 2 tables, submitted to Ap
Ambiguous Tests of General Relativity on Cosmological Scales
There are a number of approaches to testing General Relativity (GR) on linear
scales using parameterized frameworks for modifying cosmological perturbation
theory. It is sometimes assumed that the details of any given parameterization
are unimportant if one uses it as a diagnostic for deviations from GR. In this
brief report we argue that this is not necessarily so. First we show that
adopting alternative combinations of modifications to the field equations
significantly changes the constraints that one obtains. In addition, we show
that using a parameterization with insufficient freedom significantly tightens
the apparent theoretical constraints. Fundamentally we argue that it is almost
never appropriate to consider modifications to the perturbed Einstein equations
as being constraints on the effective gravitational constant, for example, in
the same sense that solar system constraints are. The only consistent
modifications are either those that grant near-total freedom, as in
decomposition methods, or ones which map directly to a particular part of
theory space
C-Band All-Sky Survey: A First Look at the Galaxy
We present an analysis of the diffuse emission at 5 GHz in the first quadrant
of the Galactic plane using two months of preliminary intensity data taken with
the C-Band All Sky Survey (C-BASS) northern instrument at the Owens Valley
Radio Observatory, California. Combining C-BASS maps with ancillary data to
make temperature-temperature plots we find synchrotron spectral indices of
between 0.408 GHz and 5 GHz and between 1.420 GHz and 5 GHz for ,
. Through the subtraction of a radio recombination
line (RRL) free-free template we determine the synchrotron spectral index in
the Galactic plane () to be between
0.408 GHz and 5 GHz, with a contribution of per cent from free-free
emission at 5\,GHz. These results are consistent with previous low frequency
measurements in the Galactic plane. By including C-BASS data in spectral fits
we demonstrate the presence of anomalous microwave emission (AME) associated
with the HII complexes W43, W44 and W47 near 30 GHz, at 4.4 sigma, 3.1 sigma
and 2.5 sigma respectively. The CORNISH VLA 5 GHz source catalogue rules out
the possibility that the excess emission detected around 30\;GHz may be due to
ultra-compact HII regions. Diffuse AME was also identified at a 4 sigma level
within , between 5
GHz and 22.8 GHz.Comment: 16 pages, 9 figures, submitted to MNRAS, referee's corrections made,
awaiting for final approval for publicatio
Dark energy survey year 1 results: The lensing imprint of cosmic voids on the cosmic microwave background
Cosmic voids gravitationally lens the cosmic microwave background (CMB) radiation, resulting in a distinct imprint on degree scales. We use the simulated CMB lensing convergence map from the Marenostrum Institut de Ciencias de l’Espai (MICE) N-body simulation to calibrate our detection strategy for a given void definition and galaxy tracer density. We then identify cosmic voids in Dark Energy Survey (DES) Year 1 data and stack the Planck 2015 lensing convergence map on their locations, probing the consistency of simulated and observed void lensing signals. When fixing the shape of the stacked convergence profile to that calibrated from simulations, we find imprints at the 3σ significance level for various analysis choices. The best measurement strategies based on the MICE calibration process yield S/N ≈ 4 for DES Y1, and the best-fitting amplitude recovered from the data is consistent with expectations from MICE (A ≈ 1). Given these results as well as the agreement between them and N-body simulations, we conclude that the previously reported excess integrated Sachs–Wolfe (ISW) signal associated with cosmic voids in DES Y1 has no counterpart in the Planck CMB lensing map.This work has made use of CosmoHub (see Carretero et al. 2017).
CosmoHub has been developed by the Port d’Informacio Cient ´ ´ıfica
(PIC), maintained through a collaboration of the Institut de F´ısica
d’Altes Energies (IFAE) and the Centro de Investigaciones Energeticas, Medioambientales y Tecnol ´ ogicas (CIEMAT), and was ´
partially funded by the ‘Plan Estatal de Investigacion Cient ´ ´ıfica y
Tecnica y de Innovaci ´ on’ program of the Spanish government. ´
Funding for the DES Projects has been provided by the US Department of Energy, the US National Science Foundation, the Ministry
of Science and Education of Spain, the Science and Technology
Facilities Council of the United Kingdom, the Higher Education
Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign,
the Kavli Institute of Cosmological Physics at the University of
Chicago, the Center for Cosmology and Astro-Particle Physics at the
Ohio State University, the Mitchell Institute for Fundamental Physics
and Astronomy at Texas A&M University, Financiadora de Estudos
e Projetos, Fundac¸ao Carlos Chagas Filho de Amparo ˜ a Pesquisa do `
Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento
Cient´ıfico e Tecnologico and the Minist ´ erio da Ci ´ encia, Tecnologia ˆ
e Inovac¸ao, the Deutsche Forschungsgemeinschaft, and the Collab- ˜
orating Institutions in the Dark Energy Survey.
The Collaborating Institutions are Argonne National Laboratory,
the University of California at Santa Cruz, the University of
Cambridge, Centro de Investigaciones Energeticas, Medioambien- ´
tales y Tecnologicas-Madrid, the University of Chicago, Univer- ´
sity College London, the DES-Brazil Consortium, the University
of Edinburgh, the Eidgenossische Technische Hochschule (ETH) ¨
Zurich, Fermi National Accelerator Laboratory, the University of ¨
Illinois at Urbana-Champaign, the Institut de Ciencies de l’Espai `
(IEEC/CSIC), the Institut de F´ısica d’Altes Energies, Lawrence
Berkeley National Laboratory, the Ludwig-Maximilians Universitat¨
Munchen and the associated Excellence Cluster Universe, the Uni- ¨
versity of Michigan, the National Optical Astronomy Observatory,
the University of Nottingham, The Ohio State University, the
University of Pennsylvania, the University of Portsmouth, SLAC
National Accelerator Laboratory, Stanford University, the University
of Sussex, Texas A&M University, and the OzDES Membership
Consortium.
This paper is based in part on observations at Cerro Tololo InterAmerican Observatory, National Optical Astronomy Observatory,
which is operated by the Association of Universities for Research in
Astronomy (AURA) under a cooperative agreement with the National
Science Foundation.
The DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766
and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-
71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV2016-0597, and MDM-2015-0509, some of which include ERDF
funds from the European Union. IFAE is partially funded by the
CERCA program of the Generalitat de Catalunya.
Research leading to these results has received funding from the
European Research Council under the European Union’s Seventh
Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, 306478, and 615929. We acknowledge
support from the Brazilian Instituto Nacional de Cienciae Tecnologia ˆ
(INCT) e-Universe (CNPq grant 465376/2014-2).
This paper has been authored by Fermi Research Alliance, LLC
under Contract No. DE-AC02-07CH11359 with the US Department
of Energy, Office of Science, Office of High Energy Physics.
PV acknowledges the support from the grant MIUR PRIN 2015
‘Cosmology and Fundamental Physics: illuminating the Dark Universe with Euclid’.
AK has been supported by a Juan de la Cierva fellowship from
MINECO with project number IJC2018-037730-I. Funding for this
project was also available in part through SEV-2015-0548 and
AYA2017-89891-P.
This project has also received funding from the European Union’s
Horizon 2020 research and innovation programme under the Marie
Skłodowska-Curie grant agreement No. 754558.Peer reviewe
Probing the accelerating Universe with radio weak lensing in the JVLA Sky Survey
We outline the prospects for performing pioneering radio weak gravitational
lensing analyses using observations from a potential forthcoming JVLA Sky
Survey program. A large-scale survey with the JVLA can offer interesting and
unique opportunities for performing weak lensing studies in the radio band, a
field which has until now been the preserve of optical telescopes. In
particular, the JVLA has the capacity for large, deep radio surveys with
relatively high angular resolution, which are the key characteristics required
for a successful weak lensing study. We highlight the potential advantages and
unique aspects of performing weak lensing in the radio band. In particular, the
inclusion of continuum polarisation information can greatly reduce noise in
weak lensing reconstructions and can also remove the effects of intrinsic
galaxy alignments, the key astrophysical systematic effect that limits weak
lensing at all wavelengths. We identify a VLASS "deep fields" program (total
area ~10-20 square degs), to be conducted at L-band and with high-resolution
(A-array configuration), as the optimal survey strategy from the point of view
of weak lensing science. Such a survey will build on the unique strengths of
the JVLA and will remain unsurpassed in terms of its combination of resolution
and sensitivity until the advent of the Square Kilometre Array. We identify the
best fields on the JVLA-accessible sky from the point of view of overlapping
with existing deep optical and near infra-red data which will provide crucial
redshift information and facilitate a host of additional compelling
multi-wavelength science.Comment: Submitted in response to NRAO's recent call for community white
papers on the VLA Sky Survey (VLASS
Semliki Forest virus induced, immune mediated demyelination: the effect of irradiation
International audienceThe Dark Energy Camera has captured a large set of images as part of Science Verification (SV) for the Dark Energy Survey (DES). The SV footprint covers a large portion of the outer Large Magellanic Cloud (LMC), providing photometry 1.5 mag fainter than the main sequence turn-off of the oldest LMC stellar population. We derive geometrical and structural parameters for various stellar populations in the LMC disc. For the distribution of all LMC stars, we find an inclination of i = -38.14° ± 0.08° (near side in the north) and a position angle for the line of nodes of θ0 = 129.51° ± 0.17°. We find that stars younger than ∼4 Gyr are more centrally concentrated than older stars. Fitting a projected exponential disc shows that the scale radius of the old populations is R>4 Gyr = 1.41 ± 0.01 kpc, while the younger population has R = 0.72 ± 0.01 kpc. However, the spatial distribution of the younger population deviates significantly from the projected exponential disc model. The distribution of old stars suggests a large truncation radius of Rt = 13.5 ± 0.8 kpc. If this truncation is dominated by the tidal field of the Galaxy, we find that the LMC is {∼eq } 24^{+9}_{-6} times less massive than the encircled Galactic mass. By measuring the Red Clump peak magnitude and comparing with the best-fitting LMC disc model, we find that the LMC disc is warped and thicker in the outer regions north of the LMC centre. Our findings may either be interpreted as a warped and flared disc in the LMC outskirts, or as evidence of a spheroidal halo component
Fast and precise map-making for massively multi-detector CMB experiments
Future cosmic microwave background (CMB) polarisation experiments aim to
measure an unprecedentedly small signal - the primordial gravity wave component
of the polarisation field B-mode. To achieve this, they will analyse huge
datasets, involving years worth of time-ordered data (TOD) from massively
multi-detector focal planes. This creates the need for fast and precise methods
to complement the M-L approach in analysis pipelines. In this paper, we
investigate fast map-making methods as applied to long duration, massively
multi-detector, ground-based experiments, in the context of the search for
B-modes. We focus on two alternative map-making approaches: destriping and TOD
filtering, comparing their performance on simulated multi-detector polarisation
data. We have written an optimised, parallel destriping code, the DEStriping
CARTographer DESCART, that is generalised for massive focal planes, including
the potential effect of cross-correlated TOD 1/f noise. We also determine the
scaling of computing time for destriping as applied to a simulated full-season
data-set for a realistic experiment. We find that destriping can out-perform
filtering in estimating both the large-scale E and B-mode angular power
spectra. In particular, filtering can produce significant spurious B-mode power
via EB mixing. Whilst this can be removed, it contributes to the variance of
B-mode bandpower estimates at scales near the primordial B-mode peak. For the
experimental configuration we simulate, this has an effect on the possible
detection significance for primordial B-modes. Destriping is a viable
alternative fast method to the full M-L approach that does not cause the
problems associated with filtering, and is flexible enough to fit into both M-L
and Monte-Carlo pseudo-Cl pipelines.Comment: 16 pages, 14 figures. MNRAS accepted. Typos corrected and computing
time/memory requirement orders-of-magnitude numbers in section 4 replaced by
precise number
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