19 research outputs found
Radio emission from dark matter annihilation in the Large Magellanic Cloud
The Large Magellanic Cloud, at only 50 kpc away from us and known to be dark
matter dominated, is clearly an interesting place where to search for dark
matter annihilation signals. In this paper, we estimate the synchrotron
emission due to WIMP annihilation in the halo of the LMC at two radio
frequencies, 1.4 and 4.8 GHz, and compare it to the observed emission, in order
to impose constraints in the WIMP mass vs. annihilation cross section plane. We
use available Faraday rotation data from background sources to estimate the
magnitude of the magnetic field in different regions of the LMC's disc, where
we calculate the radio signal due to dark matter annihilation. We account for
the e+ e- energy losses due to synchrotron, Inverse Compton Scattering and
bremsstrahlung, using the observed hydrogen and dust temperature distribution
on the LMC to estimate their efficiency. The extensive use of observations,
allied with conservative choices adopted in all the steps of the calculation,
allow us to obtain very realistic constraints.Comment: 9 pages, 7 figure
Photometric type Ia supernova surveys in narrow band filters
We study the characteristics of a narrow band type Ia supernova survey
through simulations based on the upcoming Javalambre Physics of the
accelerating universe Astrophysical Survey (J-PAS). This unique survey has the
capabilities of obtaining distances, redshifts, and the SN type from a single
experiment thereby circumventing the challenges faced by the resource-intensive
spectroscopic follow-up observations. We analyse the flux measurements
signal-to-noise ratio and bias, the supernova typing performance, the ability
to recover light curve parameters given by the SALT2 model, the photometric
redshift precision from type Ia supernova light curves and the effects of
systematic errors on the data. We show that such a survey is not only feasible
but may yield large type Ia supernova samples (up to 250 supernovae at
per month of search) with low core collapse contamination ( per
cent), good precision on the SALT2 parameters (average ,
and ) and on the distance modulus (average
, assuming an intrinsic scatter
), with identified systematic uncertainties
. Moreover, the
filters are narrow enough to detect most spectral features and obtain excellent
photometric redshift precision of , apart from 2 per
cent of outliers. We also present a few strategies for optimising the survey's
outcome. Together with the detailed host galaxy information, narrow band
surveys can be very valuable for the study of supernova rates, spectral feature
relations, intrinsic colour variations and correlations between supernova and
host galaxy properties, all of which are important information for supernova
cosmological applications.Comment: 20 pages, 12 tables and 26 figures. Version accepted by MNRAS, with
results slightly different from previous on
J-PLUS: A first glimpse at spectrophotometry of asteroids -- The MOOJa catalog
Context: The Javalambre Photometric Local Universe Survey (J-PLUS) is an
observational campaign that aims to obtain photometry in 12 ultraviolet-visible
filters (0.3-1 {\mu}m) of approximately 8 500 deg{^2} of the sky observable
from Javalambre (Teruel, Spain). Due to its characteristics and strategy of
observation, this survey will let us analyze a great number of Solar System
small bodies, with improved spectrophotometric resolution with respect to
previous large-area photometric surveys in optical wavelengths. Aims: The main
goal of this work is to present here the first catalog of magnitudes and colors
of minor bodies of the Solar System compiled using the first data release (DR1)
of the J-PLUS observational campaign: the Moving Objects Observed from
Javalambre (MOOJa) catalog. Methods: Using the compiled photometric data we
obtained very-low-resolution reflectance (photospectra) spectra of the
asteroids. We first used a {\sigma}-clipping algorithm in order to remove
outliers and clean the data. We then devised a method to select the optimal
solar colors in the J-PLUS photometric system. These solar colors were computed
using two different approaches: on one hand, we used different spectra of the
Sun, convolved with the filter transmissions of the J-PLUS system, and on the
other, we selected a group of solar-type stars in the J-PLUS DR1, according to
their computed stellar parameters. Finally, we used the solar colors to obtain
the reflectance spectra of the asteroids. Results: We present photometric data
in the J-PLUS filters for a total of 3 122 minor bodies (3 666 before outlier
removal), and we discuss the main issues of the data, as well as some
guidelines to solve the
Stochastic background of relic gravitons in a bouncing quantum cosmological model
The spectrum and amplitude of the stochastic background of relic gravitons produced in a bouncing universe is calculated. the matter content of the model consists of dust and radiation fluids, and the bounce occurs due to quantum cosmological effects when the universe approaches the classical singularity in the contracting phase. the resulting amplitude is very small and it cannot be observed by any present and near future gravitational wave detector. Hence, as in the ekpyrotic model, any observation of these relic gravitons will rule out this type of quantum cosmological bouncing model.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Universidade Federal de São Paulo, UNIFESP, Lab Fis Teor & Comp Cient, BR-09913030 Diadema, SP, BrazilCtr Brasileiro Pesquisas Fis, ICRA, BR-22290180 Rio de Janeiro, BrazilInst Nacl Pesquisas Espaciais, BR-12227010 Sao Jose Dos Campos, SP, BrazilUniv Fed Rio de Janeiro, Inst Fis, BR-21941972 Rio de Janeiro, BrazilUniversidade Federal de São Paulo, UNIFESP, Lab Fis Teor & Comp Cient, BR-09913030 Diadema, SP, BrazilFAPESP: 2009/15612-6CAPES: CAPES-PNPD 2940/2011CNPq: 20102011 PCICNPq: 300713/2009-6Web of Scienc