On a functional satisfying a weak Palais-Smale condition

In this paper we study a quasilinear elliptic problem whose functional satisfies a weak version of the well known Palais-Smale condition. An existence result is proved under general assumptions on the nonlinearities.Comment: 18 page

Spectrum extraction from detector plane images for the medium-resolution spectrometer of the mid-Infrared Instrument on-board the James Webb Space Telescope

The Mid-Infrared Instrument (MIRI) on-board the James Webb Space Telescope (JWST) performs mediumresolution spectroscopy in the 5 to 28.5micron wavelength range. In this paper two algorithms are presented that will be used to extract 1D spectra from the 2D absolutely calibrated detector science frames acquired with the Medium-Resolution Spectrometer (MRS) of MIRI. The first spectral extraction algorithm performs standard aperture photometry on point and extended sources. The second algorithm, applicable only to point sources, uses the instrument point spread function (PSF) and the pixel signal variance as a weighting function, to extract the signal from the detector pixels in an optimized way. This "optimal" extraction is also optimal in the case of faint source observations. The two algorithms are tested on MIRI ground test data and compared. For point sources, the optimal extraction algorithm is found to be more reliable than the aperture extraction algorithm

Wavelength calibration of the JWST-MIRI medium resolution spectrometer

We present the wavelength and spectral resolution characterisation of the Integral Field Unit (IFU) Medium Resolution Spectrometer for the Mid-InfraRed Instrument (MIRI), to fly onboard the James Webb Space Telescope in 2014. We use data collected using the Verification Model of the instrument and develop an empirical method to calibrate properties such as wavelength range and resolving power in a portion of the spectrometer's full spectral range (5-28 microns). We test our results against optical models to verify the system requirements and combine them with a study of the fringing pattern in the instrument's detector to provide a more accurate calibration. We show that MIRI's IFU spectrometer will be able to produce spectra with a resolving power above R=2800 in the wavelength range 6.46-7.70 microns, and that the unresolved spectral lines are well fitted by a Gaussian profile.Comment: 12 pages, submitted to SPIE Proceedings vol. 7731, Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wav

Disk galaxies with broken luminosity profiles from cosmological simulations

We present SPH cosmological simulations of the formation of three disk galaxies with a detailed treatment of chemical evolution and cooling. The resulting galaxies have properties compatible with observations: relatively high disk-to-total ratios, thin stellar disks and good agreement with the Tully-Fisher and the luminosity-size relations. They present a break in the luminosity profile at 3.0 +- 0.5 disk scale lengths, while showing an exponential mass profile without any apparent breaks, in line with recent observational results. Since the stellar mass profile is exponential, only differences in the stellar populations can be the cause of the luminosity break. Although we find a cutoff for the star formation rate imposed by a density threshold in our star formation model, it does not coincide with the luminosity break and is located at 4.3 +- 0.4 disk scale lengths, with star formation going on between both radii. The color profiles and the age profiles are "U-shaped", with the minimum for both profiles located approximately at the break radius. The SFR to stellar mass ratio increases until the break, explaining the coincidence of the break with the minimum of the age profile. Beyond the break we find a steep decline in the gas density and, consequently, a decline in the SFR and redder colors. We show that most stars (64-78%) in the outer disk originate in the inner disk and afterwards migrate there. Such stellar migrations are likely the main origin of the U-shaped age profile and, therefore, of the luminosity break.Comment: 8 pages, 4 figures. Accepted by ApJ

Primera atención psicológica: resultados preliminares de la aplicación de un protocolo innovador en víctimas de catástrofes ambientales para la prevención de trastornos de ansiedad

En los últimos años la Argentina ha tenido que enfrentar una serie de eventos catastróficos (inundaciones, accidentes ferroviarios, incendios, explosiones, etc) que han dejado diverso grado de secuelas en la salud mental de la población. La atención de las víctimas en los primeros instantes posteriores al evento resulta crucial, no sólo para el cuidado de la integridad física, sino también para la prevención de toda una variedad de trastornos de la ansiedad que afectan la salud mental (estrés postraumático, ataques de pánico, agorafobias, depresión, etc.). Este último aspecto de la salud ha sido descuidado por no contar en nuestro país con protocolos de intervención actualizados según los aportes de las neurociencias. El protocolo de Primera Atención Psicológica (PAP) provee a los socorristas, psicólogos, asistentes sociales, bomberos, policías, enfermeros, voluntarios, etc. de herramientas sencillas y eficaces para prevenir estos trastornos de ansiedad. A través de ellas, se induce a las víctimas a que activen diversas regiones de la corteza frontal, implicada en la toma de decisiones, a fin de inhibir la actividad exacerbada del cerebro límbico, producto de estrés derivado de la situación vivida, sacando de esta manera a las víctimas del estado catatónico, disminuyendo así el riesgo de trauma psicológico. A su vez, el uso de este protocolo permite modificar el estado de histeria que presentan, algunas víctimas, reduciendo su agresividad y desorganización. La importancia del estudio de situaciones de catástrofes se justifica por los efectos colaterales que estas producen en la salud de una comunidad, ocasionar provocar trastornos físicos y psicológicos. Por tal motivo, resulta central la intervención programada de recursos humanos entrenados en la toma de decisiones y las acciones eficaces, así como la sustentabilidad de tales competencias operativas tendientes a promover la prevención y reducción del riesgo y su articulación con las instituciones gubernamentales de protección civil. Desde esta perspectiva, el Instituto Universitario del Ejército (IUE), como parte del sistema universitario nacional y en el contexto de las acciones de cooperación académica y científica que llevan a cabo las universidades nacionales, desarrolla un plan de trabajo integrado por una serie de proyectos articulados y formación de recursos humanos en red. Este plan es pertinente con las políticas del Ministerio de Defensa en materia de asistencia a situaciones de emergencias y los proyectos que integran el plan se enmarcan en las áreas prioritarias definidas por el Ministerio. El IUE, a través de un acuerdo con la Universidad de Tell Hai (Israel), con el apoyo de la UNTREF, la UNCa y la UAI, efectuó una capacitación intensiva con representantes de los distintos actores sociales mencionados con un posterior ejercicio de simulacro de accidente ferroviario que involucró a más de 200 personas. Todo el ejercicio fue documentado en video. Los análisis preliminares son el objeto de este trabajo.publishedVersio

Cosmic Evolution of Stellar Disk Truncations: From z~1 to the Local Universe

We have conducted the largest systematic search so far for stellar disk truncations in disk-like galaxies at intermediate redshift (z<1.1), using the Great Observatories Origins Deep Survey South (GOODS-S) data from the Hubble Space Telescope - ACS. Focusing on Type II galaxies (i.e. downbending profiles) we explore whether the position of the break in the rest-frame B-band radial surface brightness profile (a direct estimator of the extent of the disk where most of the massive star formation is taking place), evolves with time. The number of galaxies under analysis (238 of a total of 505) is an order of magnitude larger than in previous studies. For the first time, we probe the evolution of the break radius for a given stellar mass (a parameter well suited to address evolutionary studies). Our results suggest that, for a given stellar mass, the radial position of the break has increased with cosmic time by a factor 1.3+/-0.1 between z~1 and z~0. This is in agreement with a moderate inside-out growth of the disk galaxies in the last ~8 Gyr. In the same period of time, the surface brightness level in the rest-frame B-band at which the break takes place has increased by 3.3+/-0.2 mag/arcsec^2 (a decrease in brightness by a factor of 20.9+/-4.2). We have explored the distribution of the scale lengths of the disks in the region inside the break, and how this parameter relates to the break radius. We also present results of the statistical analysis of profiles of artificial galaxies, to assess the reliability of our results.Comment: 22 pages, 14 figures, accepted for publication in ApJ. Figures 1, 3 and 6 have somehow downgraded resolution to match uploading requirement

Radial Distribution of Near-UV Flux in Disc Galaxies in the range 0<z<1

(Abridged) The goal of this paper is to quantify the changes on the SF distribution within the disc galaxies in the last ~8 Gyr. We use as a proxy for the SF radial profile the Near-UV surface brightness distributions, allowing suitably for extinction. We compare the effective radii (R_eff) and concentration of the flux distribution in the rest-frame Near-UV for a sample of 270 galaxies in the range 0<z<1. This radial distribution is compared to that measured in the rest-frame B-band, which traces older stellar populations. The analysis is performed using deep, high resolution, multi-band images from GALEX, SDSS, and HST/ACS - GOODS-South. The relation R_eff(NUV)- M* suffers a moderate change between z~1 and z~0: at a fixed stellar mass of 1E10 M_sun, galaxies increase their effective radii by a factor 1.18+/-0.06. Median profiles in NUV show signs of truncation at R~R_eff, and median colour profiles (NUV-B) show a minimum (a "bluest" point) also around R~1-1.5 R_eff. The distributions of NUV flux are more compact at z~1 than nowadays, in terms of the fraction of flux enclosed in a specific radius (in kpc). Our results indicate that the SF surface density has decreased dramatically in discs since z~1, and this decline has been more intense in the central parts (<~R_eff) of the galaxies. In addition, our data suggest that the bulges/pseudo-bulges have grown in surface brightness with regard to the discs since z~1.Comment: 26 pages, 21 figures, accepted for publication in Astronomy & Astrophysics on March 21s

Non-radial sign-changing solutions for the Schroedinger-Poisson problem in the semiclassical limit

We study the existence of nonradial sign-changing solutions to the Schroedinger-Poisson system in dimension N>=3. We construct nonradial sign-changing multi-peak solutions whose peaks are displaced in suitable symmetric configurations and collapse to the same point. The proof is based on the Lyapunov-Schmidt reduction