125 research outputs found
Assessment of Quality of Work Life for the Administrative Staff of Iraq's Public Sector Hotels
Food, Nutrition and Institution Administratio
The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-ray Background
The spectral shapes of the contributions of different classes of unresolved
gamma-ray emitters can provide insight into their relative contributions to the
extragalactic gamma-ray background (EGB) and the natures of their spectra at
GeV energies. We calculate the spectral shapes of the contributions to the EGB
arising from BL Lacertae type objects (BL Lacs) and flat-spectrum radio quasars
(FSRQs) assuming blazar spectra can be described as broken power laws. We fit
the resulting total blazar spectral shape to the Fermi Large Area Telescope
measurements of the EGB, finding that the best-fit shape reproduces well the
shape of the Fermi EGB for various break scenarios. We conclude that a scenario
in which the contribution of blazars is dominant cannot be excluded on spectral
grounds alone, even if spectral breaks are shown to be common among Fermi
blazars. We also find that while the observation of a featureless (within
uncertainties) power-law EGB spectrum by Fermi does not necessarily imply a
single class of contributing unresolved sources with featureless individual
spectra, such an observation and the collective spectra of the separate
contributing populations determine the ratios of their contributions. As such,
a comparison with studies including blazar gamma-ray luminosity functions could
have profound implications for the blazar contribution to the EGB, blazar
evolution, and blazar gamma-ray spectra and emission.Comment: 8 pages, emulateapj format; 5 figures; accepted for publication in
Ap
SXDF-UDS-CANDELS-ALMA 1.5 arcmin deep survey
We have conducted 1.1 mm ALMA observations of a contiguous or 1.5 arcmin window in the SXDF-UDS-CANDELS. We achieved a 5
sensitivity of 0.28 mJy, providing a flat sensus of dusty star-forming galaxies
with (for =40K) up to
thanks to the negative K-correction at this wavelength. We detected 5
brightest sources (S/N6) and 18 low-significance sources (5S/N4; these
may contain spurious detections, though). One of the 5 brightest ALMA sources
( mJy) is extremely faint in the WFC3 and
VLT/HAWK-I images, demonstrating that a contiguous ALMA imaging survey is able
to uncover a faint dust-obscured population that is invisible in deep
optical/near-infrared surveys. We found a possible [CII]-line emitter at
or a low- CO emitting galaxy within the field, which may allow us
to constrain the [CII] and/or the CO luminosity functions across the history of
the universe.Comment: 4 pages, 2 figures, 1 table, to appear in the proceedings of IAU
Symposium 319 "Galaxies at High Redshift and Their Evolution over Cosmic
Time", eds. S. Kaviraj & H. Ferguso
Components of the Extragalactic Gamma Ray Background
We present new theoretical estimates of the relative contributions of
unresolved blazars and star-forming galaxies to the extragalactic gamma-ray
background (EGB) and discuss constraints on the contributions from alternative
mechanisms such as dark matter annihilation and truly diffuse gamma-ray
production. We find that the Fermi source count data do not rule out a scenario
in which the EGB is dominated by emission from unresolved blazars, though
unresolved star-forming galaxies may also contribute significantly to the
background, within order-of-magnitude uncertainties. In addition, we find that
the spectrum of the unresolved star-forming galaxy contribution cannot explain
the EGB spectrum found by EGRET at energies between 50 and 200 MeV, whereas the
spectrum of unresolved FSRQs, when accounting for the energy-dependent effects
of source confusion, could be consistent with the combined spectrum of the
low-energy EGRET EGB measurements and the Fermi-LAT EGB measurements.Comment: version accepted for publication in the Astrophysical Journa
Background model systematics for the Fermi GeV excess
The possible gamma-ray excess in the inner Galaxy and the Galactic center
(GC) suggested by Fermi-LAT observations has triggered a large number of
studies. It has been interpreted as a variety of different phenomena such as a
signal from WIMP dark matter annihilation, gamma-ray emission from a population
of millisecond pulsars, or emission from cosmic rays injected in a sequence of
burst-like events or continuously at the GC. We present the first comprehensive
study of model systematics coming from the Galactic diffuse emission in the
inner part of our Galaxy and their impact on the inferred properties of the
excess emission at Galactic latitudes and 300 MeV to 500
GeV. We study both theoretical and empirical model systematics, which we deduce
from a large range of Galactic diffuse emission models and a principal
component analysis of residuals in numerous test regions along the Galactic
plane. We show that the hypothesis of an extended spherical excess emission
with a uniform energy spectrum is compatible with the Fermi-LAT data in our
region of interest at CL. Assuming that this excess is the extended
counterpart of the one seen in the inner few degrees of the Galaxy, we derive a
lower limit of ( CL) on its extension away from the GC. We
show that, in light of the large correlated uncertainties that affect the
subtraction of the Galactic diffuse emission in the relevant regions, the
energy spectrum of the excess is equally compatible with both a simple broken
power-law of break energy GeV, and with spectra predicted by the
self-annihilation of dark matter, implying in the case of final
states a dark matter mass of GeV.Comment: 65 pages, 28 figures, 7 table
Analysis of In Vivo Nuclear Factor-B Activation during Liver Inflammation in Mice: Prevention by Catalase Delivery
ABSTRACT Nuclear factor-B (NF-B) is a transcription factor that plays crucial roles in inflammation, immunity, cell proliferation, and apoptosis. Until now, there have been few studies of NF-B activation in whole animals because of experimental difficulties. Here, we show that mice receiving a simple injection of plasmid vectors can be used to examine NF-B activation in the liver. Two plasmid vectors, pNF-B-Luc (firefly luciferase gene) and pRL-SV40 (Renilla reniformis luciferase gene), were injected into the tail vein of mice by the hydrodynamics-based procedure, an established method of gene transfer to mouse liver. Then, the ratio of the firefly and R. reniformis luciferase activities (F/R) was used as an indicator of the NF-B activity in the liver. Injection of thioacetamide or lipopolysaccharide plus D-galactosamine increased the F/R ratio in the liver, and this was significantly (P Ͻ 0.001) inhibited by an intravenous injection of catalase derivatives targeting liver nonparenchymal cells. Imaging the firefly luciferase expression in live mice clearly demonstrated that the catalase derivatives efficiently prevented the NF-B-mediated expression of the firefly luciferase gene. Plasma transaminases and the survival rate of mice supported the findings obtained by the luminescence-based analyses. Thus, this method, which requires no genetic recombination techniques, is highly sensitive to the activation of NF-B and allows us to continuously examine the activation in live animals. In conclusion, this novel, simple, and sensitive method can be used not only for analyzing the NF-B activation in the organ under different inflammatory conditions but also for screening drug candidates for the prevention of liver inflammation
Tomography of the Fermi-LAT \u3b3-Ray Diffuse Extragalactic Signal via Cross Correlations with Galaxy Catalogs
Building on our previous cross-correlation analysis (Xia et al. 2011) between the isotropic \u3b3-ray background (IGRB) and different tracers of the large-scale structure of the universe, we update our results using 60 months of data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi). We perform a cross-correlation analysis both in configuration and spherical harmonics space between the IGRB and objects that may trace the astrophysical sources of the IGRB: QSOs in the Sloan Digital Sky Survey (SDSS) DR6, the SDSS DR8 Main Galaxy Sample, luminous red galaxies (LRGs) in the SDSS catalog, infrared-selected galaxies in the Two Micron All Sky Survey (2MASS), and radio galaxies in the NRAO VLA Sky Survey (NVSS). The benefit of correlating the Fermi-LAT signal with catalogs of objects at various redshifts is to provide tomographic information on the IGRB, which is crucial in separating the various contributions and clarifying its origin. The main result is that, unlike in our previous analysis, we now observe a significant (>3.5\u3c3) cross-correlation signal on angular scales smaller than 1\ub0in the NVSS, 2MASS, and QSO cases and, at lower statistical significance ( 3c3.0\u3c3), with SDSS galaxies. The signal is stronger in two energy bands, E > 0.5 GeV and E > 1 GeV, but it is also seen at E > 10 GeV. No cross-correlation signal is detected between Fermi data and the LRGs. These results are robust against the choice of the statistical estimator, estimate of errors, map cleaning procedure, and instrumental effects. Finally, we test the hypothesis that the IGRB observed by Fermi-LAT originates from the summed contributions of three types of unresolved extragalactic sources: BL Lacertae objects (BL Lacs), flat spectrum radio quasars (FSRQs), and star-forming galaxies (SFGs). We find that a model in which the IGRB is mainly produced by SFGs (% with 2\u3c3 errors), with BL Lacs and FSRQs giving a minor contribution, provides a good fit to the data. We also consider a possible contribution from misaligned active galactic nuclei, and we find that, depending on the details of the model and its uncertainty, they can also provide a substantial contribution, partly degenerate with the SFG one. \ua9 2015. The American Astronomical Society
The Fermi-LAT high-latitude Survey: Source Count Distributions and the Origin of the Extragalactic Diffuse Background
This is the first of a series of papers aimed at characterizing the
populations detected in the high-latitude sky of the {\it Fermi}-LAT survey. In
this work we focus on the intrinsic spectral and flux properties of the source
sample. We show that when selection effects are properly taken into account,
{\it Fermi} sources are on average steeper than previously found (e.g. in the
bright source list) with an average photon index of 2.40 over the
entire 0.1--100\,GeV energy band. We confirm that FSRQs have steeper spectra
than BL Lac objects with an average index of 2.48 versus
2.18. Using several methods we build the deepest source count
distribution at GeV energies deriving that the intrinsic source (i.e. blazar)
surface density at F\,ph cm s is
0.12\,deg. The integration of the source count
distribution yields that point sources contribute 16\,\% (7\,\%
systematic uncertainty) of the GeV isotropic diffuse background. At the fluxes
currently reached by LAT we can rule out the hypothesis that point-like sources
(i.e. blazars) produce a larger fraction of the diffuse emission.Comment: Version replaced to match the published one. Contact authors: M.
Ajello and A. Tramacer
Avaliação de populações de planorbídeos, em habitats naturais, pelo método de perfuração da concha
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