Separation of foregrounds from cosmic microwave background observations with the MAP satellite

Simulated observations of a 10\dg \times 10\dg field by the Microwave Anisotropy Probe (MAP) are analysed in order to separate cosmic microwave background (CMB) emission from foreground contaminants and instrumental noise and thereby determine how accurately the CMB emission can be recovered. The simulations include emission from the CMB, the kinetic and thermal Sunyaev-Zel'dovich (SZ) effects from galaxy clusters, as well as Galactic dust, free-free and synchrotron. We find that, even in the presence of these contaminating foregrounds, the CMB map is reconstructed with an rms accuracy of about 20 $\mu$K per 12.6 arcmin pixel, which represents a substantial improvement as compared to the individual temperature sensitivities of the raw data channels. We also find, for the single 10\dg \times 10\dg field, that the CMB power spectrum is accurately recovered for \ell \la 600.Comment: 7 pages, 7 figures, MNRAS submitte

L'ús del coneixement compartit per a ensenyar i aprendre

En aquest treball es descriuen i analitzen els usos del marc social de referència i del marc específic de referència com a mecanismes semiòtics que apareixen en el discurs dels participants en la interacció. Aquests mecanismes acompleixen funcions relacionades amb l’establiment inicial d’un corpus de significats compartits, la seva ampliació, i la resolució d’incomprensions i malentesos. En concret, l’estudi d’aquests mecanismes implica la comprensió de com l’ús d’experiències que suposadament són compartides entre els participants en la interacció intervé en el servei de la construcció d’esferes cada cop més amples d’intersubjectivitat. Els conceptes proposats per a referir-nos al corpus de coneixements suposadament compartits, recurs en el marc social de referència i recurs al marc específic de referència, provenen de diferents estudis (Pla, 1989; Coll et al. 1992, 1995, 1996) dirigits a la seva delimitació conceptual i empírica. En aquest treball s’il·lustren aquests mecanismes semiòtics mitjançant els resultats d’una investigació sobre influència educativa en la interacció entre mare i fill. Aquests resultats s’inscriuen en un projecte d’investigació més ampli dirigit a l’estudi dels mecanismes d’influència educativa en diferents situacions educatives (escolars i no escolars) que, prenent la concepció constructivista com a marc teòric de referència, ha permès l’elaboració d’un model d’anàlisi de la interactivitat (Coll et alt. 1992, 1995).This paper describes and analyzes the uses of the social reference framework and of the specific reference framework as semiotic mechanisms that appear in the interaction participants’ discourse. The mechanisms have different functions related to the initial establishment of a shared meaning corpus, its widening and the solving of misunderstandings. Especially, the study of these mechanisms implies understanding how the use of experiences that supposedly are shared by interaction participants takes part in the construction of ever wider spheres of intersubjectivity. The proposed concepts to refer to the supposedly shared knowledge corpus, resource in the social reference framework and resource in the specific reference framework are taken from different studies (Pla, 1989; Coll et al. 1992, 1995, 1996) targeted at its conceptual and empirical delimitation. This study shows these semiotic mechanisms by the use of the results of an investigation on the educational influence in the interaction between mother and son. These results are part of an wider investigation project aimed at the study of the educational influence mechanisms in different educational situations (in and out of the school) which, considering the constructivist conception as the theoretical reference framework, has enabled the creation of an interactivity analysis model (Coll et al. 1992, 1995).En este trabajo se describen y analizan los usos del marco social de referencia y del marco específico de referencia como mecanismos semióticos que aparecen en el discurso de los participantes en la interacción. Estos mecanismos cumplen funciones relacionadas con el establecimiento inicial de un corpus de significados compartidos, su ampliación, y la resolución de incomprensiones y malentendidos. En concreto, el estudio de estos mecanismos implica la comprensión de como el uso de experiencias que supuestamente son compartidas entre los participantes en la interacción interviene en el servicio de la construcción de esferas cada vez más amplias de intersubjetividad. Los conceptos propuestos para referirnos al corpus de conocimientos supuestamente compartidos, recurso en el marco social de referencia y recurso al marco específico de referencia, provienen de diferentes estudios (Pla, 1989; Coll et al. 1992, 1995, 1996) dirigidos a su delimitación conceptual y empírica. En este trabajo se ilustran estos mecanismos semióticos mediante los resultados de una investigación sobre influencia educativa en la interacción entre madre e hijo. Estos resultados se inscriben en un proyecto de investigación más amplio dirigido al estudio de los mecanismos de influencia educativa en diferentes situaciones educativas (escolares y no escolares) que, tomando la concepción constructivista como marco teórico de referencia, ha permitido la elaboración de un modelo de análisis de la interactividad (Coll et alt. 1992, 1995)

The Diffuse Supernova Neutrino Background is detectable in Super-Kamiokande

The Diffuse Supernova Neutrino Background (DSNB) provides an immediate opportunity to study the emission of MeV thermal neutrinos from core-collapse supernovae. The DSNB is a powerful probe of stellar and neutrino physics, provided that the core-collapse rate is large enough and that its uncertainty is small enough. To assess the important physics enabled by the DSNB, we start with the cosmic star formation history of Hopkins & Beacom (2006) and confirm its normalization and evolution by cross-checks with the supernova rate, extragalactic background light, and stellar mass density. We find a sufficient core-collapse rate with small uncertainties that translate into a variation of +/- 40% in the DSNB event spectrum. Considering thermal neutrino spectra with effective temperatures between 4-6 MeV, the predicted DSNB is within a factor 4-2 below the upper limit obtained by Super-Kamiokande in 2003. Furthermore, detection prospects would be dramatically improved with a gadolinium-enhanced Super-Kamiokande: the backgrounds would be significantly reduced, the fluxes and uncertainties converge at the lower threshold energy, and the predicted event rate is 1.2-5.6 events /yr in the energy range 10-26 MeV. These results demonstrate the imminent detection of the DSNB by Super-Kamiokande and its exciting prospects for studying stellar and neutrino physics.Comment: 14 pages, 5 figures, 4 tables, some added discussions, accepted for publication in Physical Review

Wavelet-based methodology for [15O]-H20 PET brain activation assessment

[Abstract] AMI International Conference 2003, September 21-27, Madrid, Spain: "High Resolution Molecular Imaging: from Basic Science to Clinical Applications"Statistical parametric mapping (SPM) is a voxel-byvoxel analysis method commonly used for the detection of brain activation patterns. An alternative approach is the use of multiscale information by means of wavelet analysis. In this study, we have compared the detection of brain activations using conventional SPM and a statistical wavelet analysis in a set of realistic simulated [15O]-H20 positron emission tomography (PET) phantomsPublicad

Exploring the Gamma Ray Horizon with the next generation of Gamma Ray Telescopes. Part 1: Theoretical predictions

The physics potential of the next generation of Gamma Ray Telescopes in exploring the Gamma Ray Horizon is discussed. It is shown that the reduction in the Gamma Ray detection threshold might open the window to use precise determinations of the Gamma Ray Horizon as a function of the redshift to either put strong constraints on the Extragalactic Background Light modeling or to obtain relevant independent constraints in some fundamental cosmological parameters.Comment: Updated contents, 19 pages, 8 figure

The infrared luminosity function of galaxies at redshifts z=1 and z~2 in the GOODS fields

We present the rest-frame 8 micron luminosity function (LF) at redshifts z=1 and ~2, computed from Spitzer 24 micron-selected galaxies in the GOODS fields over an area of 291 sq. arcmin. Using classification criteria based on X-ray data and IRAC colours, we identify the AGN in our sample. The rest-frame 8 micron LF for star-forming galaxies at redshifts z=1 and ~2 have the same shape as at z~0, but with a strong positive luminosity evolution. The number density of star-forming galaxies with log_{10}(nu L_nu(8 micron))>11 increases by a factor >250 from redshift z~0 to 1, and is basically the same at z=1 and ~2. The resulting rest-frame 8 micron luminosity densities associated with star formation at z=1 and ~2 are more than four and two times larger than at z~0, respectively. We also compute the total rest-frame 8 micron LF for star-forming galaxies and AGN at z~2 and show that AGN dominate its bright end, which is well-described by a power-law. Using a new calibration based on Spitzer star-forming galaxies at 0<z<0.6 and validated at higher redshifts through stacking analysis, we compute the bolometric infrared (IR) LF for star-forming galaxies at z=1 and ~2. We find that the respective bolometric IR luminosity densities are (1.2+/-0.2) x 10^9 and (6.6^{+1.2}_{-1.0}) x 10^8 L_sun Mpc^{-3}, in agreement with previous studies within the error bars. At z~2, around 90% of the IR luminosity density associated with star formation is produced by luminous and ultraluminous IR galaxies (LIRG and ULIRG), with the two populations contributing in roughly similar amounts. Finally, we discuss the consistency of our findings with other existing observational results on galaxy evolution.Comment: Accepted for publication in the ApJ. 33 pages, 15 figures. Uses emulateap

Cosmic Background dipole measurements with Planck-High Frequency Instrument

This paper discusses the Cosmic Background (CB) dipoles observations in the framework of the Planck mission. Dipoles observations can be used in three ways: (i) It gives a measurement of the peculiar velocity of our Galaxy which is an important observation in large scale structures formation model. (ii) Measuring the dipole can give unprecedent information on the monopole (that can be in some cases hard to obtain due to large foreground contaminations). (iii) The dipole can be an ideal absolute calibrator, easily detectable in cosmological experiments. Following the last two objectives, the main goal of the work presented here is twofold. First, we study the accuracy of the Planck-HFI calibration using the Cosmic Microwave Background (CMB) dipole measured by COBE as well as the Earth orbital motion dipole. We show that we can reach for HFI, a relative calibration between rings of about 1% and an absolute calibration better than 0.4% for the CMB channels (in the end, the absolute calibration will be limited by the uncertainties on the CMB temperature). We also show that Planck will be able to measure the CMB dipole direction at better than 1.7 arcmin and improve on the amplitude. Second, we investigate the detection of the Cosmic Far-Infrared Background (FIRB) dipole. Measuring this dipole could give a new and independent determination of the FIRB for which a direct determination is quite difficult due to Galactic dust emission contamination. We show that such a detection would require a Galactic dust emission removal at better than 1%, which will be very hard to achieve.Comment: 10 pages, 13 figures, submitted to A&A, uses aa.sty V5.