12,242 research outputs found
Discovery of the first giant double radio relic in a galaxy cluster found in the PLANCK Sunyaev-Zel'dovich cluster survey: PLCK G287.0+32.9
We report the discovery of large scale diffuse non-thermal radio emission in
PLCK G287.0+32.9, an exceptionally hot (T ~ 13 keV), massive and luminous
galaxy cluster, strongly detected by the PLANCK satellite in a recent, all-sky
blind search for new clusters through Sunyaev-Zel'dovich effect. Giant
Metrewave Radio telescope 150 MHz and Very Large Array 1.4 GHz radio data
reveal a pair of giant (>1 Mpc) "arc" shaped peripheral radio-relics
(signatures of shock waves) of unprecedented scale (linear separation ~4.4 Mpc
at redshift 0.39), located at distances from the cluster center which are about
0.7 and 1.3 of the cluster's virial radius. Another possible giant relic and a
radio-halo is detected closer to the cluster center. These relic sources are
unique "signposts" of extremely energetic mergers and shocks (both ongoing and
past), that are assembling and heating up this very massive galaxy cluster.
They are also a probe of the filamentary cosmic-web structure beyond the
cluster virial radius. Optical imaging with the IUCAA 2 meter telescope and
XMM-Newton X-ray data confirm a very rich galaxy cluster with a morphologically
disturbed core region, suggesting a dynamically perturbed merging system.Comment: This version matches with the published version in Astrophysical
Journal Letter
Non-Planck equilibrium radiation in plasma model of early Universe
Consideration of the adiabatic character of radiation expansion in early
Universe leads to the conclusion that equilibrium distribution of the
primordial radiation in the presence of charged particles could be different
from the Planck distribution in some regions of the spectrum. The equilibrium
distribution of electromagnetic radiation (the black body radiation) is
generalized for the system containing an extremely dense fully ionized plasma.
The conditions of the adiabatic expansion of radiation for the model of the
early Universe are found.Comment: 10 pages, 4 figure
Confirmation of the detection of B-modes in the Planck polarization maps
One of the main problems for extracting the Cosmic Microwave Background (CMB)
from submm/mm observations is to correct for the Galactic components, mainly
synchrotron, free - free and thermal dust emission with the required accuracy.
Through a series of papers, it has been demonstrated that this task can be
fulfilled by means of simple neural networks with high confidence. The main
purpose of this paper is to demonstrate that the CMB BB power spectrum detected
in the Planck 2015 polarization maps is present in the improved Planck 2017
maps with higher signal-to-noise ratio. Two features have been detected in the
EB power spectrum in the new data set, both with S/N 4 . The origin of
these features is most likely leakage from E to B with a level of about 1 per
cent. This leakage gives no significant contribution to the detected BB power
spectrum. The TB power spectrum is consistent with a zero signal. Altogether,
the BB power spectrum is not consistent with the 'canonical' tensor-to-scalar
models combined with gravitational lensing spectra. These results will give
additional strong arguments for support to the proposed polarization satellite
projects to follow up on the Planck mission .Comment: accepted for puplication in Astronomical Note
Far-Infrared to Millimeter Astrophysical Dust Emission. II: Comparison of the Two-Level Systems (TLS) model with Astronomical Data
In a previous paper we proposed a new model for the emission by amorphous
astronomical dust grains, based on solid-state physics. The model uses a
description of the Disordered Charge Distribution (DCD) combined with the
presence of Two-Level Systems (TLS) defects in the amorphous solid composing
the grains. The goal of this paper is to confront this new model to
astronomical observations of different Galactic environments in the FIR/submm,
in order to derive a set of canonical model parameters to be used as a Galactic
reference to be compared to in future Galactic and extragalactic studies. We
confront the TLS model with existing astronomical data. We consider the average
emission spectrum at high latitudes in our Galaxy as measured with FIRAS and
WMAP, as well as the emission from Galactic compact sources observed with
Archeops, for which an inverse relationship between the dust temperature and
the emissivity spectral index has been evidenced. We show that, unlike models
previously proposed which often invoke two dust components at different
temperatures, the TLS model successfully reproduces both the shape of the
Galactic SED and its evolution with temperature as observed in the Archeops
data. The best TLS model parameters indicate a charge coherence length of
\simeq 13 nm and other model parameters in broad agreement with expectations
from laboratory studies of dust analogs. We conclude that the millimeter excess
emission, which is often attributed to the presence of very cold dust in the
diffuse ISM, is likely caused solely by TLS emission in disordered amorphous
dust grains. We discuss the implications of the new model, in terms of mass
determinations from millimeter continuum observations and the expected
variations of the emissivity spectral index with wavelength and dust
temperature. The implications for the analysis of the Herschel and Planck
satellite data are discussed.Comment: Accepted for publication in A&A (16 pages, 9 figures, 6 tables
No Pulsar Kicks from Deformed Neutrinospheres
In a supernova core, magnetic fields cause a directional variation of the
neutrino refractive index so that resonant flavor oscillations would lead to a
deformation of the "neutrinosphere" for, say, tau neutrinos. The associated
anisotropic neutrino emission was proposed as a possible origin of the observed
pulsar proper motions. We argue that this effect was vastly overestimated
because the variation of the temperature over the deformed neutrinosphere is
not an adequate measure for the anisotropy of neutrino emission. The neutrino
flux is generated inside the neutron star core and is transported through the
atmosphere at a constant luminosity, forcing the temperature gradient in the
atmosphere to adjust to the inflow of energy from below. Therefore, no emission
anisotropy is caused by a deformation of the neutrinosphere to lowest order. An
estimate of the higher-order corrections must take into account the modified
atmospheric temperature profile in response to the deformation of the
neutrinosphere and the corresponding feedback on the core. We go through this
exercise in the framework of a simplified model which can be solved
analytically.Comment: Final version with minor corrections, to be published in PRD.
Includes a "Note Added" in response to astro-ph/981114
Einstein's fluctuation formula. A historical overview
A historical overview is given on the basic results which appeared by the
year 1926 concerning Einstein's fluctuation formula of black-body radiation, in
the context of light-quanta and wave-particle duality. On the basis of the
original publications (from Planck's derivation of the black-body spectrum and
Einstein's introduction of the photons up to the results of Born, Heisenberg
and Jordan on the quantization of a continuum) a comparative study is presented
on the first line of thoughts that led to the concept of quanta. The nature of
the particle-like fluctuations and the wave-like fluctuations are analysed by
using several approaches. With the help of the classical probability theory, it
is shown that the infinite divisibility of the Bose distribution leads to the
new concept of classical poissonian photo-multiplets or to the binary
photo-multiplets of fermionic character. As an application, Einstein's
fluctuation formula is derived as a sum of fermion type fluctuations of the
binary photo-multiplets.Comment: 34 page
On the explanation for quantum statistics
The concept of classical indistinguishability is analyzed and defended
against a number of well-known criticisms, with particular attention to the
Gibbs' paradox. Granted that it is as much at home in classical as in quantum
statistical mechanics, the question arises as to why indistinguishability, in
quantum mechanics but not in classical mechanics, forces a change in
statistics. The answer, illustrated with simple examples, is that the
equilibrium measure on classical phase space is continuous, whilst on Hilbert
space it is discrete. The relevance of names, or equivalently, properties
stable in time that can be used as names, is also discussed.Comment: 23 pages, 3 figures; to appear in Studies in the History and
Philosophy of Modern Physic
The ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey (REFLEX II) I. Newly identified X-ray luminous clusters at z>=0.2
We report 19 intermediate redshift clusters newly detected in the ROSAT
All-Sky survey that are spectroscopically confirmed. They form a part of 911
objects in the REFLEX II cluster catalogue with a limiting flux of
1.8\times10^12 erg/s/cm2 in the 0.1-2.4 keV ROSAT band at redshift z >= 0.2. In
addition we report three clusters from the REFLEX III supplementary catalogue,
which contains objects below the REFLEX II flux limit but satisfies the
redshift constraint above. These clusters are spectroscopically followed-up by
our ESO NTT-EFOSC2 campaigns for the redshift measurement. We describe our
observing and data reduction methods. We show how X-ray properties such as
spectral hardness ratio and source extent can be used as important diagnostics
in selecting galaxy cluster candidates. Physical properties of the clusters are
subsequently calculated from the X-ray observations. This sample contains the
high mass and intermediate-redshift galaxy clusters for astrophysical and
cosmological applications.Comment: Astronomy and Astrophysics (in press
Planck 2013 results. XXII. Constraints on inflation
We analyse the implications of the Planck data for cosmic inflation. The Planck nominal mission temperature anisotropy measurements, combined with the WMAP large-angle polarization, constrain the scalar spectral index to be ns = 0:9603 _ 0:0073, ruling out exact scale invariance at over 5_: Planck establishes an upper bound on the tensor-to-scalar ratio of r < 0:11 (95% CL). The Planck data thus shrink the space of allowed standard inflationary models, preferring potentials with V00 < 0. Exponential potential models, the simplest hybrid inflationary models, and monomial potential models of degree n _ 2 do not provide a good fit to the data. Planck does not find statistically significant running of the scalar spectral index, obtaining dns=dln k = 0:0134 _ 0:0090. We verify these conclusions through a numerical analysis, which makes no slowroll approximation, and carry out a Bayesian parameter estimation and model-selection analysis for a number of inflationary models including monomial, natural, and hilltop potentials. For each model, we present the Planck constraints on the parameters of the potential and explore several possibilities for the post-inflationary entropy generation epoch, thus obtaining nontrivial data-driven constraints. We also present a direct reconstruction of the observable range of the inflaton potential. Unless a quartic term is allowed in the potential, we find results consistent with second-order slow-roll predictions. We also investigate whether the primordial power spectrum contains any features. We find that models with a parameterized oscillatory feature improve the fit by __2 e_ _ 10; however, Bayesian evidence does not prefer these models. We constrain several single-field inflation models with generalized Lagrangians by combining power spectrum data with Planck bounds on fNL. Planck constrains with unprecedented accuracy the amplitude and possible correlation (with the adiabatic mode) of non-decaying isocurvature fluctuations. The fractional primordial contributions of cold dark matter (CDM) isocurvature modes of the types expected in the curvaton and axion scenarios have upper bounds of 0.25% and 3.9% (95% CL), respectively. In models with arbitrarily correlated CDM or neutrino isocurvature modes, an anticorrelated isocurvature component can improve the _2 e_ by approximately 4 as a result of slightly lowering the theoretical prediction for the ` <_ 40 multipoles relative to the higher multipoles. Nonetheless, the data are consistent with adiabatic initial conditions
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