On the origin of two unidentified radio/X-ray sources discovered with XMM-Newton

We aim at clarifying the nature of the emission of two spatially related unidentified X-ray sources detected with XMM-Newton telescope at intermediate-low Galactic latitude. Observations reveal a point-like source aligned with elongated diffuse emission. The X-ray spectra are best-fitted by absorbed power laws with photon indices ~1.7 for the point-like and ~2.0 for the extended one. Both sources show nonthermal radio-continuum counterparts that might indicate a physical association. From the available data, we did not detect variability on the point-like source in several timescales. Two possible scenarios are analyzed: first, based on HI line absorption, assuming a Galactic origin, we infer a distance upper bound of <2 kpc, which poses a constraint on the height over the Galactic plane of <200 pc and on the linear size of the system of 10^32 erg/s and >7.5 x 10^32 erg/s, for the point-like and extended sources, respectively; second, an extra-Galactic nature is discussed, where the point-like source might be the core of a radio galaxy and the extended source its lobe. In this case, we compare derived fluxes, spectral indices, and spatial correlation with those typical from the radio galaxy population, showing the feasibility of this alternative astrophysical scenario. From the available observational evidence, we suggest that the most promising scenario to explain the nature of these sources is a system consisting of a one-sided radio galaxy, where the point-like source is an active galactic nucleus and the extended source corresponds to the emission from its lobe. Other possibilities include a PSR/PWN origin, where the radio/X-ray emission originates from the synchrotron cooling of relativistic particles in the PSR magnetic field or a casual alignment between two unrelated sources, such as an AGN core and a Galactic X-ray blob.Comment: 6 pages, 2 figures. Accepted for publication in Astronomy and Astrophysics (A&A

The Cherenkov Telescope Array: status and perspectives

Fil: Medina, M. C. Instituto Argentino de Radioastronomía, Buenos Aires, ArgentinaFil: Orellana, Mariana. Instituto Argentino de Radioastronomía, Buenos Aires, ArgentinaFil: Romero, Gustavo E. Instituto Argentino de Radioastronomía, Buenos Aires, ArgentinaFil: Orellana, Mariana. CONICET, ArgentinaThe progress of the ground-based γ-ray Astronomy in the last 10 years (mainly due to instruments such as H.E.S.S., MAGIC and VERITAS) has inspired the scientific community to go for the next step in the evolution of the ground-based Imaging Atmospheric Cherenkov Technique (IACT). CTA has been conceived as an array of Cherenkov telescopes working as an open observatory, covering a wide energy range (∼ 30 GeV to 100 TeV), with an enhanced sensitivity and improved spatial, temporal and energy resolution. The design phase of CTA has been completed and the project is in the middle of its preparatory phase. The begin of the construction is foreseen for 2014. In this paper we describe the status of the project, the technical challenges and we give an insight on the involved physics.El progreso de la astronomía de rayos γ basada en tierra en los últimos 10 años (principalmente debido a instrumentos como H.E.S.S., MAGIC y VERITAS) ha inspirado a la comunidad científica a dar el siguiente paso en la evolución de las imágenes atmosféricas basadas en tierra. Técnica Cherenkov (IACT). CTA ha sido concebido como un conjunto de telescopios Cherenkov que funcionan como un observatorio abierto, que cubre un amplio rango de energía (∼ 30 GeV a 100 TeV), con una sensibilidad mejorada y una mejor resolución espacial, temporal y energética. La fase de diseño de CTA se ha completado y el proyecto se encuentra en la mitad de su fase preparatoria. El inicio de la construcción está previsto para 2014. En este artículo describimos el estado del proyecto, los desafíos técnicos y damos una idea de la física involucrada

On the ongoing multiple blowout in NGC 604

Several facts regarding the structure of NGC 604 are examined here. The three main cavities, produced by the mechanical energy from massive stars which in NGC 604 are spread over a volume of 10$^6$ pc$^3$, are shown here to be undergoing blowout into the halo of M33. High resolution long slit spectroscopy is used to track the impact from massive stars while HST archive data is used to display the asymmetry of the nebula. NGC 604 is found to be a collection of photoionized filaments and sections of shells in direct contact with the thermalized matter ejected by massive stars. The multiple blowout events presently drain the energy injected by massive stars and thus the densest photoionized gas is found almost at rest and is expected to suffer a slow evolution.Comment: 15 pages (11 text), 4 figures. To be published in Ap

Electromagnetic cascades propagating from low-redshift blazars

Fil: Orellana, Mariana. Universidad Nacional de Río Negro. Río Negro, Argentina.Fil: Orellana, Mariana. Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Argentina.Fil: Pellizza, L. Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Argentina.Fil: Romero, Gustavo E. Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Argentina.Fil: Tueros, Matias. Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Argentina.Fil: Medina, M. Clementina. Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Argentina.Fil: Pedrosa, Susana. Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Argentina.Fil: Romero, Gustavo E. Instituto Argentino de Radioastronomía (IAR), Argentina.Fil: Pedrosa, Susana. Instituto de Astronomía y Física del Espacio (CONICET-UBA), Argentina.Artículo de actas correspondiente a la 57° Reunión Anual de la Asociación Argentina de Astronomía; 2014, Córdoba, ArgentinaSe ha establecido que la luz de fondo extragaláctica atenúa los fotones de muy alta energía emitidos por los blazares a través de la producción de pares. Los pares son desviados por el Campo Magnético Extragaláctico (EGMF) y enfriados por la dispersión Compton Inversa con los fotones del Fondo Cósmico de Microondas (CMB) mientras desarrollan una cascada electromagnética. El EGMF también puede extraer energía de los pares en forma de radiación de sincrotrón. El espectro emitido originalmente, la extensión de la fuente y el tiempo de llegada de los fotones son modificados por tales cascadas. Para estudiar este problema asumimos que la emisión original del blazar sigue una ley de potencia con corte exponencial y rastreamos las trayectorias tridimensionales de cada partícula y fotón en la cascada. En este trabajo describimos los resultados de simulaciones numéricas respecto a la propagación de rayos -a través de escalas Mpc, enfocándonos en la construcción del espectro resultante que resulta de la conservación de energía y así combina la información de los diferentes canales de pérdidas de energía. Surgen diferentes espectros al variar la fuerza EGMF.It has been established that the Extragalactic Background Light attenuates the very high-energy photons emitted by blazars through pair production. The pairs are deflected by the Extragalactic Magnetic Field (EGMF) and cooled down by Inverse Compton scattering with the Cosmic Microwave Background (CMB) photons while they develop an electromagnetic cascade. The EGMF may also take out energy from the pairs in the form of synchrotron radiation. The originally emitted spectrum, the source extent and the arriving time of the photons are modified by such cascades. In order to study this problem we assume the blazar original emission to follow a power-law with exponential cutoff, and track the three-dimensional trajectories of each particle and photon in the cascade. In this work we describe the results of numerical simulations regarding the -ray propagation through Mpc scales, making focus on the construction of the outcoming spectrum which results from the energy conservation and thus combines the information from the different channels of energy losses. Different spectra arise when varying the EGMF strength

Deflection of ultra high energy cosmic rays by the galactic magnetic field: from the sources to the detector

We report the results of 3D simulations of the trajectories of ultra-high energy protons and Fe nuclei (with energies $E = 4 \times 10^{19}$ and $2.5 \times 10^{20} eV$) propagating through the galactic magnetic field from the sources to the detector. A uniform distribution of anti-particles is backtracked from the detector, at the Earth, to the halo of the Galaxy. We assume an axisymmetric, large scale spiral magnetic field permeating both the disc and the halo. A normal field component to the galactic plane ($B_z$) is also included in part of the simulations. We find that the presence of a large scale galactic magnetic field does not generally affect the arrival directions of the protons, although the inclusion of a $B_z$ component may cause significant deflection of the lower energy protons ($E = 4 \times 10^{19}$ eV). Error boxes larger than or equal to $\sim 5^{\circ}$ are most expected in this case. On the other hand, in the case of heavy nuclei, the arrival direction of the particles is strongly dependent on the coordinates of the particle source. The deflection may be high enough ($> 20^{\circ}$) as to make extremely difficult any identification of the sources unless the real magnetic field configuration is accurately determined. Moreover, not every incoming particle direction is allowed between a given source and the detector. This generates sky patches which are virtually unobservable from the Earth. In the particular case of the UHE events of Yakutsk, Fly's Eye, and Akeno, they come from locations for which the deflection caused by the assumed magnetic field is not significant.Comment: LaTeX + 2 postscript figures - Color versions of both figures (highly recommended) available via anonymous ftp at ftp://capc07.ast.cam.ac.uk/pub/uhecr_gmf as fig*.g

Serendipitous discovery of RR Lyrae stars in the Leo V ultra-faint galaxy

During the analysis of RR Lyrae stars discovered in the High cadence Transient Survey (HiTS) taken with the Dark Energy Camera at the 4-m telescope at Cerro Tololo Inter-American Observatory, we found a group of three very distant, fundamental mode pulsator RR Lyrae (type ab). The location of these stars agrees with them belonging to the Leo V ultra-faint satellite galaxy, for which no variable stars have been reported to date. The heliocentric distance derived for Leo V based on these stars is 173 +/- 5 kpc. The pulsational properties (amplitudes and periods) of these stars locate them within the locus of the Oosterhoff II group, similar to most other ultra-faint galaxies with known RR Lyrae stars. This serendipitous discovery shows that distant RR Lyrae stars may be used to search for unknown faint stellar systems in the outskirts of the Milky Way.Comment: Accepted in ApJ Letter

Physiological and biochemical responses of Eucalyptus seedlings to hypoxia

International audienceAbstractKey messageHypoxia promoted distinct changes in the levels of hormones, amino acids and organic acids in the roots and shoots of a seedling from 2Eucalyptusclones. These results indicate that modulation of hormone production, as well as specific chemical constituents associated with primary metabolism, contributes to the regulation of growth ofEucalyptusseedlings under hypoxic conditions.ContextAlthough floods in areas under Eucalyptus cultivation in Brazil negatively affect plant growth, chemical markers and/or indicators of hypoxia contributes to the regulation.sAimsThis study aimed to evaluate the hormonal and metabolic alterations induced by hypoxia on seedling growth.MethodsSeedlings of Eucalyptus urograndis clones VCC 975 and 1004 were grown in liquid solution and submitted to bubbling with air or with nitrogen. Levels of indol-3-acetic acid (IAA), abscisic acid (ABA), ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC), primary metabolite profile and photosynthetic parameters were evaluated after fourteen days.ResultsHypoxia did not affect shoot dry mass of the seedlings. However, it decreased stomatal conductance and photosynthetic CO2 assimilation rate, and increased levels of ABA in the shoot. Hypoxia greatly reduced the dry mass and volume of roots, concomitantly with higher ACC and ethylene production. Moreover, hypoxia promoted distinct changes in IAA levels, and in amino acid and organic acid metabolism in roots and shoots.ConclusionThe biosynthesis of ABA, ethylene and IAA and its quantity in root tissues indicates the regulation of metabolism in response to hypoxia in Eucalyptus clones

Enseñanza basada en la problemática social como base de la prevención

Las actividades para los alumnos que cursan la asignatura Odontología Preventiva y Social son la de participar activamente en la acción educadora de la sociedad, a cuyos integrantes debe concienciar sobre sus responsabilidades y deberes en el cuidado de su propia salud; entre ellas está la promoción de la salud a través de la educación individual y colectiva, para lo cual utilizan los medios masivos de comunicación oral y escrita. En el despliegue de las actividades para Educación de la Salud Individual en la comunidad, se trabaja con folletería y afiches que son repartidos puerta a puerta y colocados en lugares de convocatoria pública y en comercios de la zona; estas actividades se elaboran de manera tal que logren el mejor impacto en la comunidad. Además se despliegan actividades educativas (charlas informativas) respecto a Salud Bucal y Promoción de la Salud en colegios, comedores escolares, clubes, Iglesias y demás centros de concurrencia masiva. Estos puntos estratégicos son seleccionados previo a un diagnóstico de la comunidad, teniendo en cuenta que uno de los principales objetivos es crear agentes multiplicadores de Salud Bucal. Las charlas son ilustradas con material didáctico como láminas ilustrativas, títeres con macromodelos, macrocepillos de madera, espejos, etc. Otra actividad que desarrollan los alumnos, es la confección de un cuaderno de campo, donde se vuelcan las tareas realizadas por el grupo: 1.- Relevamiento de la zona, 2.- Recolección de datos del universo a estudiar a través de encuestas domiciliarias, 3.- Documentación fotográfica, 4.- Tabulación de datos con criterio estadístico, y, 5.- Devolución de resultados obtenidos a los líderes comunitarios. De esta manera, cursantes de la asignatura Odontología Preventiva y Social que cumplen tareas Extramuros trabajaron en dos comunidades periféricas del Gran La Plata durante el año 2010, asumiendo como objetivos que el alumno sea capaz de conocer las necesidades de la población, determinar prioridades, tomando como premisa el concepto de salud, para obtener comunidades saludables que sean partícipes en su propio beneficio. Diseñar instrumentos necesarios para poder determinar el estado de salud – enfermedad en la comunidad donde están insertos. Los resultados obtenidos demuestran una grave desigualdad existente en el estado de salud bucal de la población, diferencias sociales muy marcadas, donde las necesidades básicas insatisfechas se interpusieron en nuestra labor diaria, al mismo tiempo creencias y valores presentes en la sociedad conllevaron al éxito y al fracaso de nuestra labor en las diferentes zonas

The Power of High Precision Broadband Photometry: Tracing the Milky Way Density Profile with Blue Horizontal Branch stars in the Dark Energy Survey

Blue Horizontal Branch (BHB) stars, excellent distant tracers for probing the Milky Way's halo density profile, are distinguished in the $(g-r)_0$ vs $(i-z)_0$ color space from another class of stars, blue straggler stars (BSs). We develop a Bayesian mixture model to classify BHB stars using high-precision photometry data from the Dark Energy Survey Data Release 2 (DES DR2). We select $\sim2100$ highly-probable BHBs based on their $griz$ photometry and the associated uncertainties, and use these stars to map the stellar halo over the Galactocentric radial range $20 \lesssim R \lesssim 70$ kpc. After excluding known stellar overdensities, we find that the number density $n_\star$ of BHBs can be represented by a power law density profile $n_\star \propto R^{-\alpha}$ with an index of $\alpha=4.28_{-0.12}^{+0.13}$, consistent with existing literature values. In addition, we examine the impact of systematic errors and the spatial inhomogeneity on the fitted density profile. Our work demonstrates the effectiveness of high-precision $griz$ photometry in selecting BHB stars. The upcoming photometric survey from the Rubin Observatory, expected to reach depths 2-3 magnitudes greater than DES during its 10-year mission, will enable us to investigate the density profile of the Milky Way's halo out to the virial radius, unravelling the complex processes of formation and evolution in our Galaxy.Comment: 22 pages, 18 figures. Submitted AAS Journal. Comments Welcome Code used in this work can be found at: https://github.com/sazabi4/Yu2024_BHB