On the Radio Polarization Signature of Efficient and Inefficient Particle Acceleration in Supernova Remnant SN 1006

We present a radio polarization study of SN 1006, based on combined VLA and ATCA observations at 20 cm that resulted in sensitive images with an angular resolution of 10 arcsec. The fractional polarization in the two bright radio and X-ray lobes of the SNR is measured to be 0.17, while in the southeastern sector, where the radio and non-thermal X-ray emission are much weaker, the polarization fraction reaches a value of 0.6 +- 0.2, close to the theoretical limit of 0.7. We interpret this result as evidence of a disordered, turbulent magnetic field in the lobes, where particle acceleration is believed to be efficient, and a highly ordered field in the southeast, where the acceleration efficiency has been shown to be very low. Utilizing the frequency coverage of our observations, an average rotation measure of ~12 rad/m2 is determined from the combined data set, which is then used to obtain the intrinsic direction of the magnetic field vectors. While the orientation of magnetic field vectors across the SNR shell appear radial, a large fraction of the magnetic vectors lie parallel to the Galactic Plane. Along the highly polarized southeastern rim, the field is aligned tangent to the shock, and therefore also nearly parallel to the Galactic Plane. These results strongly suggest that the ambient field surrounding SN 1006 is aligned with this direction (i.e., from northeast to southwest) and that the bright lobes are due to a polar cap geometry. Our study establishes that the most efficient particle acceleration and generation of magnetic turbulence in SN 1006 is attained for shocks in which the magnetic field direction and shock normal are quasi-parallel, while inefficient acceleration and little to no generation of magnetic turbulence obtains for the quasi-perpendicular case.Comment: Accepted for publication in Astronomical Journa

An Atomic and Molecular Study of the Interstellar Medium Around the SNR RCW 103

We report on the detection of HCO+ and 12CO emission in the rotational transition J=1-0 in the vicinity of the shock front at the southern border of the supernova remnant RCW 103, where previous infrared observations suggest an interaction with a molecular cloud. The observations were carried out with the Australian Millimeter Radiotelescope at Mopra. We observed a depletion of HCO+ behind the supernova shock front. In addition, we studied the interstellar medium over an extended region towards RCW 103 based on archival 21 cm HI line observations from the Australia Telescope Compact Array (ATCA) and the Parkes Telescope. No atomic gas is observed in emission in coincidence with the molecular feature. This absence is interpreted in terms of self absorption processes.Comment: accepted to be published in Publications of the Astronomical Society of Australi

A molecular shell with star formation toward the supernova remnant G349.7+0.2

A field of ~38'x38' around the supernova remnant (SNR) G349.7+0.2 has been surveyed in the CO J=1-0 transition with the 12 Meter Telescope of the NRAO, using the On-The-Fly technique. The resolution of the observations is 54". We have found that this remnant is interacting with a small CO cloud which, in turn, is part of a much larger molecular complex, which we call the ``Large CO Shell''. The Large CO Shell has a diameter of about 100 pc, an H_2 mass of 930,000 solar masses, and a density of 35 cm-3. We investigate the origin of this structure and suggest that an old supernova explosion ocurred about 4 million years ago, as a suitable hypothesis. Analyzing the interaction between G349.7+0.2 and the Large CO Shell, it is possible to determine that the shock front currently driven into the molecular gas is a non-dissociative shock (C-type), in agreement with the presence of OH 1720 MHz masers. The positional and kinematical coincidence among one of the CO clouds that constitute the Large CO Shell, an IRAS point-like source and an ultracompact H II region, indicate the presence of a recently formed star. We suggest that the formation of this star was triggered during the expansion of the Large CO Shell, and suggest the possibility that the same expansion also created the progenitor star of G349.7+0.2. The Large CO Shell would then be one of the few observational examples of supernova-induced star formation.Comment: accepted in Astronomical Journal, corrected typo in the abstract (in first line, 38' instead of 38"

Morphological evidence for azimuthal variations of the cosmic ray ion acceleration at the blast wave of SN 1006

Using radio, X-ray and optical observations, we present evidence for morphological changes due to efficient cosmic ray ion acceleration in the structure of the southeastern region of the supernova remnant SN 1006. SN 1006 has an apparent bipolar morphology in both the radio and high-energy X-ray synchrotron emission. In the optical, the shock front is clearly traced by a filament of Balmer emission in the southeast. This optical emission enables us to trace the location of the blast wave (BW) even in places where the synchrotron emission from relativistic electrons is either absent or too weak to detect. The contact discontinuity (CD) is traced using images in the low-energy X-rays (oxygen band) which we argue reveals the distribution of shocked ejecta. We interpret the azimuthal variations of the ratio of radii between the BW and CD plus the X-ray and radio synchrotron emission at the BW using CR-modified hydrodynamic models. We assumed different azimuthal profiles for the injection rate of particles into the acceleration process, magnetic field and level of turbulence. We found that the observations are consistent with a model in which these parameters are all azimuthally varying, being largest in the brightest regions.Comment: Accepted for publication in ApJ - 42 pages, 11 figure

A multi-wavelength analysis of the diffuse H II region G25.8700+0.1350

We present a multi-wavelength investigation of the H ii region G25.8700+0.1350, located in the inner part of the Galaxy. In radio continuum emission, the region is seen as a bright arc-shaped structure. An analysis of the H i line suggests that G25.8700+0.1350 lies at a distance of 6.5 kpc. The ionized gas is bordered by a photodissociation region, which is encircled by a molecular structure where four molecular clumps are detected. At infrared wavelengths, the region is also very conspicuous. Given the high level of visual absorption in the region, the exciting stars should be searched for in the infrared band. In this context, we found in the literature one Wolf–Rayet and one red supergiant, which, together with 37 2MASS sources that are candidate O-type stars, could be related to the origin of G25.8700+0.1350. Finally, as expanding H ii regions are hypothesized to trigger star formation, we used different infrared point source catalogues to search for young stellar object candidates (cYSOs). A total of 45 cYSOs were identified projected on to the molecular clouds.This project was partially financed by the Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) of Argentina under projects PIP 01299, PIP 0226, PIP 00356 and PIP 00107, and Universidad Nacional de La Plata under 2012-2014 PPID/G002 and 11/G120

High resolution HI and radio continuum observations of the SNR G290.1-0.8

We have observed the supernova remnant (SNR) G290.1-0.8 in the 21-cm HI line and the 20-cm radio continuum using the Australia Telescope Compact Array (ATCA). The HI data were combined with data from the Southern Galactic Plane Survey to recover the shortest spatial frequencies. In contrast, HI absorption was analyzed by filtering extended HI emission, with spatial frequencies shorter than 1.1 k-lambda. The low-resolution ATCA radio continuum image of the remnant shows considerable internal structure, resembling a network of filaments across its 13 arcmin diameter. A high-resolution ATCA radio continuum image was also constructed to study the small scale structure in the SNR. It shows that there are no structures smaller than ~17", except perhaps for a bright knot to the south, which is probably an unrelated object. The HI absorption study shows that the gas distribution and kinematics in front of SNR G290.1-0.8 are complex. We estimate that the SNR probably lies in the Carina arm, at a distance 7 (+/- 1) kpc. In addition, we have studied nearby sources in the observed field using archival multiwavelength data to determine their characteristics.Comment: Accepted in Monthly Notices of the Royal Astronomical Societ

Diseño y Evaluación de una Teoría de Diseño de Sistemas de Información para un Sistema Multimedia Interactivo

La Teoría de Diseño de Sistemas de Información, es una metodología propuesta por Walls y Widmeyer (1992) que consisteen un conjunto de teorías descriptivas, que ofrecen principios y guías que permiten dar soluciones a los desarrolladores ydiseñadores de sistemas, buscando lograr el diseño de herramientas de software que sean incluyentes, flexibles y que esténestrechamente integradas con las necesidades de sus usuarios (Markus and Majchrzak, 2002). Esta investigación describe eldiseño y prueba de una Teoría de Diseño de Sistemas de Información para un Sistema Multimedia Interactivo. La Teoría fuediseñada, desarrollada y probada empíricamente mediante un estudio que se llevó a cabo en la Universidad Autónoma deAguascalientes, México. El estudio identificó cómo el uso de un sistema multimedia interactivo, permite mejorar eldesempeño de los estudiantes, comparado con la enseñanza tradicional o la apoyada con el uso de páginas Web

Uso de Tecnologías de Información para la Mejora del Aprendizaje

En los últimos años las Tecnologías de Información y Comunicación han tenido un fuerte impacto en los sistemas educativos, los cuales se enfrentan con el desafío de proveer a los estudiantes herramientas y conocimientos necesarios para la mejora del aprendizaje. Este artículo describe un estudio piloto realizado en la Universidad Autónoma de Aguascalientes, México, con el programa educativo de Ingeniería en Sistemas Computacionales. El objetivo principal de este trabajo consiste en identificar si el uso de una herramienta multimedia-interactiva, especialmente diseñada para la enseñanza de estructuras de datos, puede ser una alternativa a los métodos de enseñanza tradicionales. Se aplicó un examen para evaluar los conocimientos adquiridos por el estudiante, así como para evaluar la calidad de la herramienta como lo marcan los criterios de la ingeniería de software. Los resultados muestran que la herramienta ayuda a aprender temas complejos como estructuras de datos, además cumple con aspectos de calidad