Spitzer power-law active galactic nucleus candidates in the chandra deep field-north

We define a sample of 62 galaxies in the Chandra Deep Field-North whose Spitzer IRAC SEDs exhibit the characteristic power-law emission expected of luminous AGNs. We study the multiwavelength properties of this sample and compare the AGNs selected in this way to those selected via other Spitzer color-color criteria. Only 55% of the power-law galaxies are detected in the X-ray catalog at exposures of >0.5 Ms, although a search for faint emission results in the detection of 85% of the power-law galaxies at the ≥2.5 σ detection level. Most of the remaining galaxies are likely to host AGNs that are heavily obscured in the X-ray. Because the power-law selection requires the AGNs to be energetically dominant in the near- and mid-infrared, the power-law galaxies comprise a significant fraction of the Spitzer-detected AGN population at high luminosities and redshifts. The high 24 μm detection fraction also points to a luminous population. The power-law galaxies comprise a subset of color-selected AGN candidates. A comparison with various mid-infrared color selection criteria demonstrates that while the color-selected samples contain a larger fraction of the X-ray-luminous AGNs, there is evidence that these selection techniques also suffer from a higher degree of contamination by star-forming galaxies in the deepest exposures. Considering only those power-law galaxies detected in the X-ray catalog, we derive an obscured fraction of 68% (2 : 1). Including all of the power-law galaxies suggests an obscured fraction of <81% (4 : 1).

Near-infrared and star-forming properties of local luminous infrared galaxies

We use Hubble Space Telescope (HST) NICMOS continuum and Paα observations to study the near-infrared and star formation properties of a representative sample of 30 local (d ~ 35-75 Mpc) luminous infrared galaxies (LIRGs, infrared [8-1000 μm] luminosities of log L_IR = 11-11.9 L_☉). The data provide spatial resolutions of 25-50 pc and cover the central ~3.3-7.1 kpc regions of these galaxies. About half of the LIRGs show compact (~1-2 kpc) Paα emission with a high surface brightness in the form of nuclear emission, rings, and minispirals. The rest of the sample show Paα emission along the disk and the spiral arms extending over scales of 3-7 kpc and larger. About half of the sample contains H II regions with Hα luminosities significantly higher than those observed in normal galaxies. There is a linear empirical relationship between the mid-IR 24 μm and hydrogen recombination (extinction-corrected Paα) luminosity for these LIRGs, and the H II regions in the central part of M51. This relation holds over more than four decades in luminosity, suggesting that the mid-IR emission is a good tracer of the star formation rate (SFR). Analogous to the widely used relation between the SFR and total IR luminosity of R. Kennicutt, we derive an empirical calibration of the SFR in terms of the monochromatic 24 μm luminosity that can be used for luminous, dusty galaxies.

A complete census of Herschel-detected infrared sources within the HST Frontier Fields

We present a complete census of all Herschel-detected sources within the six massive lensing clusters of the HST Frontier Fields (HFF). We provide a robust legacy catalogue of 263 sources with Herschel fluxes, primarily based on imaging from the Herschel Lensing Survey and PEP/HerMES Key Programmes. We optimally combine Herschel, Spitzer and WISE infrared (IR) photometry with data from HST, VLA and ground-based observatories, identifying counterparts to gain source redshifts. For each Herschel-detected source we also present magnification factor (mu), intrinsic IR luminosity and characteristic dust temperature, providing a comprehensive view of dust-obscured star formation within the HFF. We demonstrate the utility of our catalogues through an exploratory overview of the magnified population, including more than 20 background sub-LIRGs unreachable by Herschel without the assistance gravitational lensing.

Are long gamma-ray bursts biased tracers of star formation? Clues from the host galaxies of the Swift/BAT6 complete sample of bright LGRBs II. Star formation rates and metallicities at z < 1

Aims. Long gamma-ray bursts (LGRBs) are associated with the deaths of massive stars and might therefore be a potentially powerful tool for tracing cosmic star formation. However, especially at low redshifts (z< 1.5) LGRBs seem to prefer particular types of environment. Our aim is to study the host galaxies of a complete sample of bright LGRBs to investigate the effect of the environment on GRB formation. Methods. We studied host galaxy spectra of the Swift/BAT6 complete sample of 14 z< 1 bright LGRBs. We used the detected nebular emission lines to measure the dust extinction, star formation rate (SFR), and nebular metallicity (Z) of the hosts and supplemented the data set with previously measured stellar masses M_*. The distributions of the obtained properties and their interrelations (e.g. mass-metallicity and SFR-M_* relations) are compared to samples of field star-forming galaxies. Results. We find that LGRB hosts at z< 1 have on average lower SFRs than if they were direct star formation tracers. By directly comparing metallicity distributions of LGRB hosts and star-forming galaxies, we find a good match between the two populations up to 12 +log (O/H)~8.4−8.5, after which the paucity of metal-rich LGRB hosts becomes apparent. The LGRB host galaxies of our complete sample are consistent with the mass-metallicity relation at similar mean redshift and stellar masses. The cutoff against high metallicities (and high masses) can explain the low SFR values of LGRB hosts. We find a hint of an increased incidence of starburst galaxies in the Swift/BAT6 z< 1 sample with respect to that of a field star-forming population. Given that the SFRs are low on average, the latter is ascribed to low stellar masses. Nevertheless, the limits on the completeness and metallicity availability of current surveys, coupled with the limited number of LGRB host galaxies, prevents us from investigating more quantitatively whether the starburst incidence is such as expected after taking into account the high-metallicity aversion of LGRB host galaxies.

Search for associations containing young stars (SACY). VII. New stellar and substellar candidate members in the young associations

Context. The young associations offer us one of the best opportunities to study the properties of young stellar and substellar objects and to directly image planets thanks to their proximity (<200 pc) and age (≈5−150 Myr). However, many previous works have been limited to identifying the brighter, more active members (≈1 M_⊙) owing to photometric survey sensitivities limiting the detections of lower mass objects. Aims. We search the field of view of 542 previously identified members of the young associations to identify wide or extremely wide (1000−100 000 au in physical separation) companions. Methods. We combined 2MASS near-infrared photometry (J, H, K) with proper motion values (from UCAC4, PPMXL, NOMAD) to identify companions in the field of view of known members. We collated further photometry and spectroscopy from the literature and conducted our own high-resolution spectroscopic observations for a subsample of candidate members. This complementary information allowed us to assess the efficiency of our method. Results. We identified 84 targets (45: 0.2−1.3 M_⊙, 17: 0.08−0.2 M_⊙, 22: <0.08 M_⊙) in our analysis, ten of which have been identified from spectroscopic analysis in previous young association works. For 33 of these 84, we were able to further assess their membership using a variety of properties (X-ray emission, UV excess, Hα, lithium and K I equivalent widths, radial velocities, and CaH indices). We derive a success rate of 76–88% for this technique based on the consistency of these properties. Conclusions. Once confirmed, the targets identified in this work would significantly improve our knowledge of the lower mass end of the young associations. Additionally, these targets would make an ideal new sample for the identification and study of planets around nearby young stars. Given the predicted substellar mass of the majority of these new candidate members and their proximity, high-contrast imaging techniques would facilitate the search for new low-mass planets.

The Spanish Space Weather Service SeNMEs. A Case Study on the Sun-Earth Chain

The Spanish Space Weather Service SeNMEs, www.senores.es, is a portal created by the SRG-SW of the Universidad de Alcala, Spain, to meet societal needs of near real-time space weather services. This webpage-portal is divided in different sections to fulfill users needs about space weather effects: radio blackouts, solar energetic particle events, geomagnetic storms and presence of geomagnetically induced currents. In less than one year of activity, this service has released a daily report concerning the solar current status and interplanetary medium, informing about the chances of a solar perturbation to hit the Earth's environment. There are also two different forecasting tools for geomagnetic storms, and a daily ionospheric map. These tools allow us to nowcast a variety of solar eruptive events and forecast geomagnetic storms and their recovery, including a new local geomagnetic index, LDin, along with some specific new scaling. In this paper we also include a case study analysed by SeNMEs. Using different high resolution and cadence data from space-borne solar telescopes SDO, SOHO and GOES, along with ionospheric and geomagnetic data, we describe the Sun-Earth feature chain for the event.

Las nubes de alta velocidad de la galaxia y la estructura del gas interestelar

Este trabajo presenta resultados que se proponen aclarar ulteriormente,los aspectos morfológicos y termodinámicos del medio interestelar en las regiones periféricas de la galaxia.Se divide en una parte de análisis eminentemente teórico,en el cual se postura una estructura jerárquica del gas, en tres fases de temperatura y densidades distintas. Y en una parte de carácter observacional,en el cual se presentan los resultados de observaciones radioastronómicas que tienden a corroborar los resultados teóricos.El cuadro resultante propuesto por este estudio es el de un gas galáctico periférico conformado en estructuras nebulares, que participan en la rotación galáctica y que estando presumiblemente a grandes distancias,presentan altos valores de la velocidad radial; pueden ser interpretadas como representativa de dos fases en equilibrio de presión, térmico y de ionización entre ellas y con una tercera fase, “internebular”,a temperatura mayor que 20000º K.

Aperture effects on the oxygen abundance determinations from Califa data

This paper aims to provide aperture corrections for emission lines in a sample of spiral galaxies from the Calar Alto Legacy Integral Field Area Survey (CALIFA) database. In particular, we explore the behavior of the log([O III] λ5007/Hβ)/([N II] λ6583/Hα) (O3N2) and log[N II] lambda 6583/Hα (N2) flux ratios since they are closely connected to different empirical calibrations of the oxygen abundances in star-forming galaxies. We compute the median growth curves of Hα, Hα/Hβ, O3N2, and N-2 up to 2.5R(50) and 1.5 disk R-eff. These distances cover most of the optical spatial extent of the CALIFA galaxies. The growth curves simulate the effect of observing galaxies through apertures of varying radii. We split these growth curves by morphological types and stellar masses to check if there is any dependence on these properties. The median growth curve of the Hα flux shows a monotonous increase with radius with no strong dependence on galaxy inclination, morphological type, and stellar mass. The median growth curve of the Hα/HβH ratio monotonically decreases from the center toward larger radii, showing for small apertures a maximum value of ≈10% larger than the integrated one. It does not show any dependence on inclination, morphological type, and stellar mass. The median growth curve of N-2 shows a similar behavior, decreasing from the center toward larger radii. No strong dependence is seen on the inclination, morphological type, and stellar mass. Finally, the median growth curve of O3N2 increases monotonically with radius, and it does not show dependence on the inclination. However, at small radii it shows systematically higher values for galaxies of earlier morphological types and for high stellar mass galaxies. Applying our aperture corrections to a sample of galaxies from the SDSS survey at 0.02 ≤ z ≤ 0.3 shows that the average difference between fiber-based and aperture-corrected oxygen abundances, for different galaxy stellar mass and redshift ranges, reaches typically to ≈11%, depending on the abundance calibration used. This average difference is found to be systematically biased, though still within the typical uncertainties of oxygen abundances derived from empirical calibrations. Caution must be exercised when using observations of galaxies for small radii (e.g., below 0.5 R_eff) given the high dispersion shown around the median growth curves. Thus, the application of these median aperture corrections to derive abundances for individual galaxies is not recommended when their fluxes come from radii much smaller than either R_50 or R_eff.

Cómo ser Juanjo Sáez.

Conferencia y debate con Juanjo Sáez, uno de los dibujantes y guionistas más reconocidos de España. La sesión versó acerca de su propio trabajo desde sus inicios autoeditando fanzines hasta su realización de series de animación para TV. Todo el discurso estuvo vinculado a la resolución de problemas creativos y a la optimización en el proceso de producción de las cualidades del autor, haciendo gala de un sentido del humor particularmente coherente con el tipo de trabajo que desarrolla este artista. En sus inicios, estudió Arte, Diseño y Pintura en la Escuela Massana (Barcelona) y comenzó a colaborar en fanzines como dibujante e ilustrador. De ahí, pasó a colaborar para la revista musical Rockdelux, así como en otras revistas de carácter cultural y de tendencias. Entre otros medios, ha colaborado para el suplemento La Luna de El Mundo, la revista Qué Leer, o el diario El Periódico de Catalunya. A la vez que labró una carrera como historietista, realizó trabajos de diseño y publicitarios, y consiguió abrir su propio estudio, Familiares de Juanjo Sáez, en el barrio del Raval. Ha llegado a realizar trabajos para Nike (con motivo del Trofeo Conde de Godó) o Estrella Damm. Dentro de su obra, ha publicado varios comics. Sus primeras obras fueron Dentro del sombrero y Buenos tiempos para la muerte (Morsa, 2000), y más tarde la editorial Mondadori le publicó Viviendo del cuento (2004), El Arte, conversaciones imaginarias con mi madre (2006), Yo, otro libro egocéntrico (2010) y Arros Covat (2011). En 2012 vuelve a publicar con Ed. Morsa, en este caso el libro Nada. En 2009, colaboró con el grupo Los Planetas en la publicación de un cómic para su disco Principios básicos de astronomía, y realizó su primera serie de televisión, Arròs covat, que se emitió en el Canal33 de Televisió de Catalunya y que le valió un Premio Ondas en 2010. Ese mismo año lanzó un libro en castellano con el guión de su serie, Arroz pasado, y comenzó a colaborar para el diario Ara.

La octava esfera o la esfera de las estrellas fijas

Según el modelo cosmológico medieval, heredero directo del sistema de representación cosmológica del Mundo Antiguo, el Universo era esférico, y en su centro, inmóvil, estaba situada la Tierra. Ésta se encontraba rodeada por las esferas, “orbes”, de los siete planetas1, quedando esta estructura cerrada por la octava esfera o esfera de las estrellas fijas, en la que se disponían las constelaciones. Más allá se encontraba el primun mobile que ponía en marcha la maquinaría celeste, siendo identificado en el mundo cristiano con Dios. La esfera de las estrellas fijas se convirtió en un motivo iconográfico de gran interés a lo largo de toda la Edad Media, bien en su representación unitaria, como la octava esfera que cierra el sistema de representación cosmológica, o a través de la representación de sus constelaciones.

Optimal impulsive collision avoidance in low earth orbit

This paper presents a high-accuracy fully analytical formulation to compute the miss distance and collision probability of two approaching objects following an impulsive collision avoidance maneuver. The formulation hinges on a linear relation between the applied impulse and the objects? relative motion in the b-plane, which allows one to formulate the maneuver optimization problem as an eigenvalue problem coupled to a simple nonlinear algebraic equation. The optimization criterion consists of minimizing the maneuver cost in terms of delta-V magnitude to either maximize collision miss distance or to minimize Gaussian collision probability. The algorithm, whose accuracy is verified in representative mission scenarios, can be employed for collision avoidance maneuver planning with reduced computational cost when compared with fully numerical algorithms.

The Westerly Index as complementary indicator of the North Atlantic oscillation in explaining drought variability across Europe

This paper analyses the influence of different atmospheric circulation indices on the multi-scalar drought variability across Europe by using the Standardized Precipitation Evapotranspiration Index (SPEI). The monthly circulation indices used in this study include the North Atlantic oscillation (NAO), the East Atlantic (EA), the Scandinavian (SCAN) and the East Atlantic-Western Russia (EA-WR) patterns, as well as the recently published Westerly Index (WI), defined as the persistence of westerly winds over the eastern north Atlantic region. The results indicate that European drought variability is better explained by the station-based NAO index and the WI than by any other combination of circulation indices. In northern and central Europe the variability of drought severity for different seasons and time-scales is strongly associated with the WI. On the contrary, the influence of the NAO on southern Europe droughts is stronger than that exerted by the WI. The correlation patterns of the NAO and WI with the SPEI show a spatial complementarity in shaping drought variability across Europe. Lagged correlations of the NAO and WI with the SPEI also indicate enough skill of both indices to anticipate drought severity several months in advance. As long as instrumental series of the NAO and WI are available, their combined use would allow inferring European drought variability for the last two centuries and improve the calibration and interpretation of paleoclimatic proxies associated with drought.

Los primeros errores en la formación docente

El presente trabajo tiene por objetivo un análisis de los conocimientos matemáticos con los que los alumnos ingresan en la carrera del profesorado en matemática y astronomía del Instituto Superior del Profesorado “Dr. Joaquín V. González” de Buenos Aires (Argentina). Las conclusiones se apoyan en la experiencia de las autoras como Profesoras a cargo del Curso de Apoyo al Curso de Nivelación de la carrera antes mencionada. Esta investigación que se llevó a cabo a través de la observación y el dictado de las clases, lo que permitió analizar los errores más frecuentes y sus orígenes, los conceptos bien adquiridos, la concepción que los alumnos tienen de la Matemática y el perfil de los mismos. El análisis ha sido realizado sobre la base del aspecto constructivo del error. A partir del análisis realizado a lo largo de la investigación, se puede concluir que detrás de todo error hay un aprendizaje incompleto o erróneo.

Ciencia y Teología en el Renacimiento paleólogo entre Oriente y Occidente: el caso de Isaac Argiro

Isaac Argiro (1310-1375 ca.) siguió la estela de su maestro, Nicéforo Gregorás, tanto en el cultivo de la ciencia profana como en la oposición a la teología de Gregorio Palamás, que Argiro combatió incluso en la persona del emperador Juan VI Cantacuceno. Además de esas inclinaciones espirituales, Isaac Argiro se interesó también por la astrología, como prueba el hecho de que copiara íntegro el Laurent. Plut. 28, 13, que fue el modelo de los manuscritos que se produjeron en el círculo de Juan Abramio, el astrólogo de Andrónico IV (Laurent. Plut. 28, 16, Marc. Gr. 324, Laurent. Plut. 28, 14 y Taurin. C. VII. 10). Esta comunicación trata de estudiar la vinculación entre el interés de Argiro por la astronomía y la astrología de la Grecia Antigua y sus posiciones filosóficas y teológicas, tal como fueron expresadas en sus opúsculos antipalamitas, así como su acercamiento a los círculos intelectuales bizantinos más proclives a un entendimiento con el Papado con vistas a la unión de las Iglesias de Roma y Constantinopla.