1,091 research outputs found
A complete sample of LSP blazars fully described in -rays. New -ray detections and associations with Fermi-LAT
We study the -ray and broadband spectral energy distribution (SED)
properties of a complete sample of 104 bright, radio-selected low-synchrotron
peaked (LSP) blazars. Most of the sources have already been detected in the
-ray band by Fermi-LAT, however almost 20% of these blazars have no
counterpart in any of the Fermi catalogs so far. Using the Fermi Science Tools,
we look for -ray emission for those objects not yet reported in any
Fermi-LAT catalog. We performed a binned likelihood analysis in the 0.3-500 GeV
energy band with Fermi-LAT Pass 8 data, integrating over 7.5 years of
observations. We studied -ray light curves and test statistic (TS) maps
to validate new detections and associations. We fit the synchrotron (Syn) and
inverse Compton (IC) components for all sources using all available historical
data, enhancing the study of Syn to IC peak-power correlations. We derive the
distribution of the Compton dominance (CD) along with population properties
such as Syn and IC peak power, and frequency distributions. We deliver a unique
characterization in -rays for a complete sample of LSP blazars. We show
that three previously unidentified 3FGL sources can be associated with blazars
when using improved -ray positions obtained from TS maps. Six
previously unreported -ray sources are detected at TS>20 level, while
another three show TS values between 10-20. We evaluate two cases in which
source confusion is likely present. In four cases there is no significant
-ray signature, however short-lived flares have been detected in these
sources. Finally, the log(CD) has a Gaussian-like distribution with median
log(CD)=0.1, implying that on average the peak-power for the Syn and IC
components in LSP blazars are similar.Comment: 19 pages, 24 figures, Accepted for publication in A&
Using CMB data to constrain non-isotropic Planck-scale modifications to Electrodynamics
We develop a method to constrain non-isotropic features of Cosmic Microwave
Background (CMB) polarization, of a type expected to arise in some models
describing quantum gravity effects on light propagation. We describe the
expected signatures of this kind of anomalous light propagation on CMB photons,
showing that it will produce a non-isotropic birefringence effect, i.e. a
rotation of the CMB polarization direction whose observed amount depends in a
peculiar way on the observation direction. We also show that the sensitivity
levels expected for CMB polarization studies by the \emph{Planck} satellite are
sufficient for testing these effects if, as assumed in the quantum-gravity
literature, their magnitude is set by the minute Planck length.Comment: 18 pages, 4 figures, 2 table
Influencia de la inyección alternante de aire en el color y el “alambrado” de aceitunas negras naturales Arauco c.v., en comparación con el método tradicional argentino
Ripe black olives cv. Arauco were processed under different conditions to evaluate the effects of alternating air injection (AI) on the color of olives and on spoilage known as “alambrado”, using a system based on the one patented by the “Instituto de la Grasa” (Sevilla, Spain), as compared with the traditional Argentine processing method, which consists of drying the olives in natural air (“extendido”) for 24 hours at 7, 14 and 21 days of fermentation. Four types of fermentation were used: brine at 2% NaCl plus AI; brine at 2% NaCl plus three “extendidos”; brine at 9% NaCl plus three “extendidos”; and brine at 9% NaCl plus AI and one “extendido”. As previously observed in other varieties by other authors, we noticed that lower pH values were achieved in 2% NaCl fermentations vs. 9% NaCl fermentations. AI prevented the “alambrado” whereas brine at 2% NaCl reduced this spoilage as compared with brine at 9% NaCl. The darkest color of olives was obtained with three “extendidos”, but 83% of brightness reduction was achieved with only one “extendido”. The “extendido” process decreased the texture. We conclude that the combination of AI and “extendido” can add benefits to natural black olives of the Arauco variety.Se elaboraron aceitunas negras maduras variedad Arauco en distintas condiciones para evaluar la inyección alternante de aire (IA) con un sistema basado en el patentado por el Instituto de la Grasa, en comparación con la elaboración tradicional argentina donde se realiza exposición al aire en seco (“extendido”) de los frutos durante 24 h, en tres momentos de la fermentación (después de 7, 14 y 21 días). Se hicieron cuatro tipos de fermentaciones: en salmuera al 2% con IA; en salmuera al 2% y 9% con tres “extendidos” y salmuera 9% con IA y un “extendido”. Se alcanzaron los valores mas bajos de pH en fermentaciones con el 2% de NaCl versus las de 9%. La IA evita el defecto de “alambrado” y lo reduce la concentración de 2% versus la de 9%. El color más oscuro se obtiene aplicando el “extendido” en tres oportunidades, pero con una aplicación se alcanza el 83% de la reducción de luminosidad alcanzada por las tres aplicaciones. La textura se ve disminuida por el proceso de “extendido”. La combinación de la IA y el “extendido” reducen el defecto de “alambrado” y oscurecen las aceitunas negras al natural de la variedad Arauco
Elliptic CMB Sky
The ellipticity of the anisotropy spots of the Cosmic Microwave Background
measured by the Wilkinson Microwave Anisotropy Probe (WMAP) has been studied.
We find an average ellipticity of about 2, confirming with a far larger
statistics similar results found first for the COBE-DMR CMB maps, and then for
the BOOMERanG CMB maps. There are no preferred directions for the obliquity of
the anisotropy spots. The average ellipticity is independent of temperature
threshold and is present on scales both smaller and larger than the horizon at
the last scattering. The measured ellipticity characteristics are consistent
with being the effect of geodesics mixing occurring in an hyperbolic Universe,
and can mark the emergence of CMB ellipticity as a new observable constant
describing the Universe. There is no way of simulating this effect. Therefore
we cannot exclude that the observed behavior of the measured ellipticity can
result from a trivial topology in the popular flat -CDM model, or from
a non-trivial topology.Comment: 10 pages, 5 figures, the version to appear in Mod.Phys.Lett.
Correlated Component Analysis for diffuse component separation with error estimation on simulated Planck polarization data
We present a data analysis pipeline for CMB polarization experiments, running
from multi-frequency maps to the power spectra. We focus mainly on component
separation and, for the first time, we work out the covariance matrix
accounting for errors associated to the separation itself. This allows us to
propagate such errors and evaluate their contributions to the uncertainties on
the final products.The pipeline is optimized for intermediate and small scales,
but could be easily extended to lower multipoles. We exploit realistic
simulations of the sky, tailored for the Planck mission. The component
separation is achieved by exploiting the Correlated Component Analysis in the
harmonic domain, that we demonstrate to be superior to the real-space
application (Bonaldi et al. 2006). We present two techniques to estimate the
uncertainties on the spectral parameters of the separated components. The
component separation errors are then propagated by means of Monte Carlo
simulations to obtain the corresponding contributions to uncertainties on the
component maps and on the CMB power spectra. For the Planck polarization case
they are found to be subdominant compared to noise.Comment: 17 pages, accepted in MNRA
A novel CMB polarization likelihood package for large angular scales built from combined WMAP and Planck LFI legacy maps
We present a CMB large-scale polarization dataset obtained by combining WMAP
Ka, Q and V with Planck 70 GHz maps. We employ the legacy frequency maps
released by the WMAP and Planck collaborations and perform our own Galactic
foreground mitigation technique, which relies on Planck 353 GHz for polarized
dust and on Planck 30 GHz and WMAP K for polarized synchrotron. We derive a
single, optimally-noise-weighted, low-residual-foreground map and the
accompanying noise covariance matrix. These are shown, through
analysis, to be robust over an ample collection of Galactic masks. We use this
dataset, along with the Planck legacy Commander temperature solution, to build
a pixel-based low-resolution CMB likelihood package, whose robustness we test
extensively with the aid of simulations, finding excellent consistency. Using
this likelihood package alone, we constrain the optical depth to reionazation
at C.L., on 54\% of the sky. Adding the
Planck high- temperature and polarization legacy likelihood, the Planck
lensing likelihood and BAO observations we find
in a full CDM exploration. The
latter bounds are slightly less constraining than those obtained employing
\Planck\ HFI CMB data for large angle polarization, that only include EE
correlations. Our bounds are based on a largely independent dataset that does
include also TE correlations. They are generally well compatible with Planck
HFI preferring slightly higher values of . We make the low-resolution
Planck and WMAP joint dataset publicly available along with the accompanying
likelihood code.Comment: The WMAP+LFI likelihood module is available on
\http://www.fe.infn.it/u/pagano/low_ell_datasets/wmap_lfi_legacy
Simultaneous Planck, Swift, and Fermi observations of X-ray and gamma-ray selected blazars
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands, with additional 5GHz flux-density limits to ensure a good probability of a Planck detection. We compare our results to those of a companion paper presenting simultaneous Planck and multi-frequency observations of 104 radio-loud northern active galactic nuclei selected at radio frequencies. While we confirm several previous results, our unique data set allows us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored. Almost all the BL Lac objects have been detected by the Fermi Large Area Telescope (LAT), whereas 30% to 40% of the flat-spectrum radio quasars (FSRQs) in the radio, soft X-ray, and hard X-ray selected samples are still below the gamma-ray detection limit even after integrating 27 months of Fermi-LAT data. The radio to sub-millimetre spectral slope of blazars is quite flat, with similar to 0 up to about 70GHz, above which it steepens to similar to -0.65. The BL Lacs have significantly flatter spectra than FSRQs at higher frequencies. The distribution of the rest-frame synchrotron peak frequency (nu(S)(peak)) in the spectral energy distribution (SED) of FSRQs is the same in all the blazar samples with = 10(13.1+.1) Hz, while the mean inverse Compton peak frequency, , ranges from 10(21) to 10(22) Hz. The distributions of nu(S)(peak) and nu(S)(peak) of BL Lacs are much broader and are shifted to higher energies than those of FSRQs; their shapes strongly depend on the selection method. The Compton dominance of blazars, defined as the ratio of the inverse Compton to synchrotron peak luminosities, ranges from less than 0.2 to nearly 100, with only FSRQs reaching values larger than about 3. Its distribution is broad and depends strongly on the selection method, with gamma-ray selected blazars peaking at similar to 7 or more, and radio-selected blazars at values close to 1, thus implying that the common assumption that the blazar power budget is largely dominated by high-energy emission is a selection effect. A comparison of our multi-frequency data with theoretical predictions shows that simple homogeneous SSC models cannot explain the simultaneous SEDs of most of the gamma-ray detected blazars in all samples. The SED of the blazars that were not detected by Fermi-LAT may instead be consistent with SSC emission. Our data challenge the correlation between bolometric luminosity and nu(S)(peak) predicted by the blazar sequence. --author-supplied descriptio
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