207 research outputs found
Constraining neutrino masses with the ISW-galaxy correlation function
Temperature anisotropies in the Cosmic Microwave Background (CMB) are
affected by the late Integrated Sachs-Wolfe (lISW) effect caused by any
time-variation of the gravitational potential on linear scales. Dark energy is
not the only source of lISW, since massive neutrinos induce a small decay of
the potential on small scales during both matter and dark energy domination. In
this work, we study the prospect of using the cross-correlation between CMB and
galaxy density maps as a tool for constraining the neutrino mass. On the one
hand massive neutrinos reduce the cross-correlation spectrum because
free-streaming slows down structure formation; on the other hand, they enhance
it through their change in the effective linear growth. We show that in the
observable range of scales and redshifts, the first effect dominates, but the
second one is not negligible. We carry out an error forecast analysis by
fitting some mock data inspired by the Planck satellite, Dark Energy Survey
(DES) and Large Synoptic Survey Telescope (LSST). The inclusion of the
cross-correlation data from Planck and LSST increases the sensitivity to the
neutrino mass m_nu by 38% (and to the dark energy equation of state w by 83%)
with respect to Planck alone. The correlation between Planck and DES brings a
far less significant improvement. This method is not potentially as good for
detecting m_nu as the measurement of galaxy, cluster or cosmic shear power
spectra, but since it is independent and affected by different systematics, it
remains potentially interesting if the total neutrino mass is of the order of
0.2 eV; if instead it is close to the lower bound from atmospheric
oscillations, m_nu ~ 0.05 eV, we do not expect the ISW-galaxy correlation to be
ever sensitive to m_nu.Comment: 10 pages, 8 figures. References added. Accepted for publication in
Phys.Rev.
Impact of Scale Dependent Bias and Nonlinear Structure Growth on the ISW Effect: Angular Power Spectra
We investigate the impact of nonlinear evolution of the gravitational
potentials in the LCDM model on the Integrated Sachs-Wolfe (ISW) contribution
to the CMB temperature power spectrum, and on the cross-power spectrum of the
CMB and a set of biased tracers of the mass. We use an ensemble of N-body
simulations to directly follow the potentials and compare results to
perturbation theory (PT). The predictions from PT match the results to high
precision for k<0.2 h/Mpc. We compute the nonlinear corrections to the angular
power spectrum and find them to be <10% of linear theory for l<100. These
corrections are swamped by cosmic variance. On scales l>100 the departures are
more significant, however the CMB signal is more than a factor 10^3 larger at
this scale. Nonlinear ISW effects therefore play no role in shaping the CMB
power spectrum for l<1500. We analyze the CMB--density tracer cross-spectrum
using simulations and renormalized bias PT, and find good agreement. The usual
assumption is that nonlinear evolution enhances the growth of structure and
counteracts linear ISW on small scales, leading to a change in sign of the
CMB-LSS cross-spectrum at small scales. However, PT analysis suggests that this
trend reverses at late times when the logarithmic growth rate
f(a)=dlnD/dlna<0.5 or om_m(a)<0.3. Numerical results confirm these expectations
and we find no sign change in ISW-LSS cross-power for low redshifts.
Corrections due to nonlinearity and scale dependence of the bias are found to
be <10% for l<100, therefore below the S/N of the current and future
measurements. Finally, we estimate the CMB--halo cross-correlation coefficient
and show that it can be made to match that for CMB--dark matter to within 5%
for thin redshift shells, mitigating the need to model bias evolution.Comment: 27 pages, 19 figure. Hi-res. version:
http://www.itp.uzh.ch/~res/NonlinearISW.HiRes.pd
Relativistic positioning: four-dimensional numerical approach in Minkowski space-time
We simulate the satellite constellations of two Global Navigation Satellite
Systems: Galileo (EU) and GPS (USA). Satellite motions are described in the
Schwarzschild space-time produced by an idealized spherically symmetric non
rotating Earth. The trajectories are then circumferences centered at the same
point as Earth. Photon motions are described in Minkowski space-time, where
there is a well known relation, Coll, Ferrando & Morales-Lladosa (2010),
between the emission and inertial coordinates of any event. Here, this relation
is implemented in a numerical code, which is tested and applied. The first
application is a detailed numerical four-dimensional analysis of the so-called
emission coordinate region and co-region. In a second application, a GPS
(Galileo) satellite is considered as the receiver and its emission coordinates
are given by four Galileo (GPS) satellites. The bifurcation problem (double
localization) in the positioning of the receiver satellite is then pointed out
and discussed in detail.Comment: 16 pages, 9 figures, published (online) in Astrophys. Space Sc
On the Rees-Sciama effect: maps and statistics
Small maps of the Rees-Sciama (RS) effect are simulated by using an
appropriate N-body code and a certain ray-tracing procedure. A method designed
for the statistical analysis of cosmic microwave background (CMB) maps is
applied to study the resulting simulations. These techniques, recently proposed
--by our team-- to consider lens deformations of the CMB, are adapted to deal
with the RS effect. This effect and the deviations from Gaussianity associated
to it seem to be too small to be detected in the near future. This conclusion
follows from our estimation of both the RS angular power spectrum and the RS
reduced n-direction correlation functions for n<7.Comment: 11 pages, 13 figures, to appear in MNRA
First bounds on the very high energy gamma-ray emission from Arp 220
Using the Major Atmospheric Gamma Imaging Cherenkov Telescope (MAGIC), we
have observed the nearest ultra-luminous infrared galaxy Arp 220 for about 15
hours. No significant signal was detected within the dedicated amount of
observation time. The first upper limits to the very high energy -ray
flux of Arp 220 are herein reported and compared with theoretical expectations.Comment: Accepted for publication in Ap
Revisión bibliográfica de implantología bucofacial del año 2007
Se expone una revisión de la literatura científica publicada en revistas indexadas durante el año 2007 sobre Implantología Bucofacial. La escasez de tiempo de que disponen los profesionales para consultar las múltiples fuentes de información, ha motivado a los autores a resumir los artículos publicados y clasificarlos en los siguientes apartados: generalidades, pacientes especiales, superficies y diseños, tejidos blandos, implantes inmediatos, carga inmediata, complicaciones, elevación sinusal, técnicas avanzadas, plasma rico en plaquetas y factores de crecimiento, cirugía guiada, cirugía mínimamente invasiva y miniimplantes, con la intención de facilitar una puesta al día
Constraints on the steady and pulsed very high energy gamma-ray emission from observations of PSR B1951+32/CTB 80 with the MAGIC Telescope
We report on very high energy gamma-observations with the MAGIC Telescope of
the pulsar PSR B1951+32 and its associated nebula, CTB 80. Our data constrain
the cutoff energy of the pulsar to be less than 32 GeV, assuming the pulsed
gamma-ray emission to be exponentially cut off. The upper limit on the flux of
pulsed gamma-ray emission above 75 GeV is 4.3*10^-11 photons cm^-2 sec^-1, and
the upper limit on the flux of steady emission above 140 GeV is 1.5*10^-11
photons cm^-2 sec^-1. We discuss our results in the framework of recent model
predictions and other studies.Comment: 7 pages, 7 figures, replaced with published versio
MAGIC upper limits on the very high energy emission from GRBs
The fast repositioning system of the MAGIC Telescope has allowed during its
first data cycle, between 2005 and the beginning of year 2006, observing nine
different GRBs as possible sources of very high energy gammas. These
observations were triggered by alerts from Swift, HETE-II, and Integral; they
started as fast as possible after the alerts and lasted for several minutes,
with an energy threshold varying between 80 and 200 GeV, depending upon the
zenith angle of the burst. No evidence for gamma signals was found, and upper
limits for the flux were derived for all events, using the standard analysis
chain of MAGIC. For the bursts with measured redshift, the upper limits are
compatible with a power law extrapolation, when the intrinsic fluxes are
evaluated taking into account the attenuation due to the scattering in the
Metagalactic Radiation Field (MRF).Comment: 25 pages, 9 figures, final version accepted by ApJ. Changet title to
"MAGIC upped limits on the VERY high energy emission from GRBs", re-organized
chapter with description of observation, removed non necessaries figures,
added plot of effective area depending on zenith angle, added an appendix
explaining the upper limit calculation, added some reference
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