On measuring the Galactic dark matter halo with hypervelocity stars

Hypervelocity stars (HVSs) travel from the Galactic Centre across the dark matter halo of the Milky Way, where they are observed with velocities in excess of the Galactic escape speed. Because of their quasi-radial trajectories, they represent a unique probe of the still poorly constrained dark matter component of the Galactic potential. In this paper, we present a new method to produce such constraints. Our likelihood is based on the local HVS density obtained by back-propagating the observed phase space position and quantifies the ejection probability along the orbit. To showcase our method, we apply it to simulated Gaia samples of $\sim200$ stars in three realistic Galactic potentials with dark matter components parametrized by spheroidal NFW profiles. We find that individual HVSs exhibit a degeneracy in the scale mass-scale radius plane ($M_s-r_s$) and are able to measure only the combination $\alpha = M_s/r_s^2$. Likewise, a degeneracy is also present between $\alpha$ and the spheroidal axis-ratio $q$. In the absence of observational errors, we show the whole sample can nail down both parameters with {\it sub-per cent} precision (about $1\%$ and $0.1\%$ for $\alpha$ and $q$ respectively) with no systematic bias. This remarkable power to constrain deviations from a symmetric halo is a consequence of the Galactocentric origin of HVSs. To compare our results with other probes, we break the degeneracy in the scale parameters and impose a mass-concentration relation. The result is a competitive precision on the virial mass $M_{200}$ of about $10\%$.Comment: See Fig. 8 for a summar

Weak lensing constraints on splashback around massive clusters

The splashback radius $r_\text{sp}$ separates the physical regimes of collapsed and infalling material around massive dark matter haloes. In cosmological simulations, this location is associated with a steepening of the spherically averaged density profile $\rho(r)$. In this work, we measure the splashback feature in the stacked weak gravitational lensing signal of $27$ massive clusters from the Cluster Canadian Comparison Project with careful control of residual systematics effects. We find that the shear introduced by the presence of additional structure along the line of sight significantly affects the noise at large clustercentric distances. Although we do not detect a significant steepening, the use of a simple parametric model enables us to measure both $r_\text{sp}=3.5^{+1.1}_{-0.7}$ comoving Mpc and the value of the logarithmic slope $\gamma = \log \rho / \log r$ at this point, $\gamma(r_\text{sp}) = -4.3^{+1.0}_{-1.5}$.Comment: 9 pages, 5 figures. Accepted for publication in MNRA

The mass-size relation of galaxy clusters

The outskirts of accreting dark matter haloes exhibit a sudden drop in density delimiting their multi-stream region. Due to the dynamics of accretion, the location of this physically motivated edge strongly correlates with the halo growth rate. Using hydrodynamical zoom-in simulations of high-mass clusters, we explore this definition in realistic simulations and find an explicit connection between this feature in the dark matter and galaxy profiles. We also show that the depth of the splashback feature correlates well with the direction of filaments and, surprisingly, the orientation of the brightest cluster galaxy. Our findings suggest that galaxy profiles and weak-lensing masses can define an observationally viable mass-size scaling relation for galaxy clusters, which can be used to extract cosmological information.Comment: 9 pages, 9 figure

Predicting the hypervelocity star population in Gaia

Hypervelocity stars (HVSs) are amongst the fastest objects in our Milky Way. These stars are predicted to come from the Galactic center (GC) and travel along unbound orbits across the Galaxy. In the coming years, the ESA satellite Gaia will provide the most complete and accurate catalogue of the Milky Way, with full astrometric parameters for more than $1$ billion stars. In this paper, we present the expected sample size and properties (mass, magnitude, spatial, velocity distributions) of HVSs in the Gaia stellar catalogue. We build three Gaia mock catalogues of HVSs anchored to current observations, exploring different ejection mechanisms and GC stellar population properties. In all cases, we predict hundreds to thousands of HVSs with precise proper motion measurements within a few tens of kpc from us. For stars with a relative error in total proper motion below $10 \%$, the mass range extends to ~$10 M_{\odot}$ but peaks at ~$1$ $M_\odot$. The majority of Gaia HVSs will therefore probe a different mass and distance range compared to the current non-Gaia sample. In addition, a subset of a few hundreds to a few thousands of HVSs with $M$ ~ $3$ $M_\odot$ will be bright enough to have a precise measurement of the three-dimensional velocity from Gaia alone. Finally, we show that Gaia will provide more precise proper motion measurements for the current sample of HVS candidates. This will help identifying their birthplace narrowing down their ejection location, and confirming or rejecting their nature as HVSs. Overall, our forecasts are extremely encouraging in terms of quantity and quality of HVS data that can be exploited to constrain both the Milky Way potential and the GC properties.Comment: 17 pages, 18 figures, accepted for publication in MNRA

Proyecto de articulación e investigación educativa entre la universidad y la Escuela Media abordada desde la salud, 2007-2012. Parte I

Este trabajo de carácter extensionista, interdisciplinario e interinstitucional presenta los siguientes propósitos: Brindar herramientas extensionistas para la vinculación desde la Universidad hacia la comunidad. Promover la articulación educativa entre el nivel medio y  la universidad. Contactar a los estudiantes secundarios con la actividad científica. Interactuar con otros colegios, creando una red Articular educativa. Los objetivos de los alumnos: Comprender que la salud es un proceso multicausal a través de la investigación e integración de contenidos. Afianzar hábitos inherentes a la investigación científica. Promover la difusión de los conocimientos adquiridos sobre la salud en su entorno. Los Temas: Virus. Clasificación. Propiedades. Patogénesis, Relación Virus-Célula. Infección-Enfermedad. Vacunas. Este trabajo de carácter extensionista, interdisciplinario e interinstitucional presenta los siguientes propósitos: Brindar herramientas extensionistas para la vinculación desde la Universidad hacia la comunidad. Promover la articulación educativa entre el nivel medio y la universidad. Contactar a los estudiantes secundarios con la actividad científica. Interactuar con otros colegios, creando una red Articular educativa. Los objetivos de los alumnos: Comprender que la salud es un proceso multicausal a través de la investigación e integración de contenidos. Afianzar hábitos inherentes a la investigación científica. Promover la difusión de los conocimientos adquiridos sobre la salud en su entorno. Los Temas: Virus. Clasificación, Propiedades, Patogénesis, Relación Virus-Célula, Infección-Enfermedad, Vacunas, Cartilla de vacunación, Diagnóstico directo e indirecto. Mostración: Observación de imágenes, fotos, placas. Bioseguridad y esterilización. Conductas Preventivas. Prevención. Laboratorios de Riesgo. Visita a Laboratorios del Instituto de Virología. Juego de roles, pautas desde la educación para la salud. Derechos y obligaciones hacia una vida sana para nosotros y los demás. Algoritmo a seguir ante infecciones como HIV, HPV, Dengue. Reflexión y concientización. Las Prácticas: Viaje a zona de estudio y captura, determinado por los investigadores. Se dividirán en grupos con experto para cada tipo de captura. Aves y roedores e insectos. Estudio del ave, roedor, insectos, clasificación y muestra. La modalidad de trabajo es el aula taller, la participación de todos los protagonistas en el proceso de enseñanza y aprendizaje. El aula se convierte en un espacio en que todos son artesanos del conocimiento y desarrollan instrumentos para abordar el objeto, de manera que todos se reconozcan en el producto de la tarea. Aula por las clases expositivas, charlas y taller por aprender haciendo o aprender por descubrimiento. Esta modalidad incluye instancias individuales y grupales. La evaluación de los alumnos es la producción final presentada en la Parte II. Seguimiento y evaluación del proyecto, es a través del registro de las observaciones, de la participación de los alumnos, las intervenciones oportunas, las respuestas adecuadas, etc. También se hace el seguimiento y ajuste de la Jornada a través de las clases dictadas para mejorar las prácticas hacia futuras Jornadas. En conclusión los destinatarios son alumnos del último año en Ciencias Naturales del secundario que comprenden lo brindado en la universidad para finalmente impactar en un sector de la comunidad con estrategias y herramientas extensionistas intentando dar respuesta

Genomic characterization and seroprevalence studies on alphaviruses in Uruguay

Alphaviruses (Togaviridae) are arboviruses frequently associated with emerging infectious diseases. In this study, we aimed to investigate the presence of alphaviruses in Uruguay by detecting the viral genome in mosquitoes and neutralizing antibodies in equines. A total of 3,575 mosquitoes were analyzed for alphavirus genome detection. Serologic studies were performed on 425 horse sera by plaque reduction neutralization test (PRNT80) against Venezuelan equine encephalitis virus (VEEV) subtype IAB, Pixuna virus (PIXV), Rio Negro virus (RNV), western equine encephalitis virus (WEEV), and Madariaga virus (MADV). Mosquitoes belonging to six genera were captured and 82.9% were identified as Culex pipiens. Two Cx. pipiens pools collected in Fray Bentos and Las Toscas localities were alphavirus positive, and phylogenetic analyses showed that the sequences grouped into two different clusters: the lineage I of eastern equine encephalitis virus and RNV (VEEV complex), respectively. Plaque reduction neutralization test assays showed antibodies against strains of the VEEV complex, MADV, and WEEV. Rio Negro virus was the most geographically widespread virus, showing higher seroprevalences (up to 20%). Seroprevalences against VEEV IAB ranged between 4.6% and 13%; antibodies against PIXV, WEEV, and MADV were less frequent (3–4%). In conclusion, RNV exhibited the highest seroprevalence in horses, a wide geographical distribution, and viral genome was detected in Cx. pipiens mosquitoes. Madariaga virus had a low seroprevalence in equines, but an epizootic lineage typical of North America was detected in Cx. pipiens mosquitoes. Taken together, our results show that alphaviruses are present in Uruguay with variable occurrence and geographical distribution being a potential threat for human and equine health

Genomic characterization of orthobunyavirus of veterinary importance in America

During 2013, in Argentina, three new isolates of serogroup Bunyamwera virus (genus Orthobunyavirus, family Peribunyaviridae)were recovered from two horses with encephalitis, and from an aborted equine fetus. In the present study, we report the complete genome sequence, genetic characterization, and phylogenetic analysis of three new strains isolated in Argentina to clarifying their relationship within the Bunyamwera serogroup virus and to investigate the evolutionary history of viruses with segmented genomes.Fil: Tauro, Laura Beatriz. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de Souza, William Marciel. Universidade de Sao Paulo; BrasilFil: Rivarola, María Elisa. Universidad Nacional de Córdoba. Facultad de Medicina. Laboratorio de Arbovirus y Arenovirus; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de Oliveira, Rodrigo. Instituto Evandro Chagas; BrasilFil: Konigheim, Brenda Salome. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Patroca Silva, Sandro. Instituto Evandro Chagas; BrasilFil: Lima, Clayton. Instituto Evandro Chagas; BrasilFil: Oliveira, Layanna. Instituto Evandro Chagas; BrasilFil: Vasconcelos, Janaina M.. Instituto Evandro Chagas; BrasilFil: Ferreira Cardoso, Jedson. Instituto Evandro Chagas; BrasilFil: Vianez Júnior, João Lídio. Instituto Evandro Chagas; BrasilFil: Teixeira Nunes, Márcio Roberto. Instituto Evandro Chagas; BrasilFil: Contigiani de Minio, Marta Silvia. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentin