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Radiation induced by relativistic electron showers in the X-ray spectrum of Active Galactic Nuclei

The iron Kα emitted from accreting black holes is thought to be produced by the reprocessing of hard X-ray radiation illuminating the disk. Mechanisms which could produce this hard X-ray radiation are magnetic reconnection in the disk corona or shocks. Both phenomena produce high energy particles whose contribution is usually ignored. In this work, we analyze how the transfer of mechanical energy from relativistic electrons to the circumnuclear gas (accretion disk, BLR) contributes to the X-ray continuum and the iron Kα emission. It is shown that for gas columns comparable to the Thomson depth, the iron Kα yield is comparable to that observed provided that the electron energy is above ∼600 keV and that the total kinetic luminosity of the beam is around log LKIN = 46.6−47.7; this luminosity is comparable to that observed in radio-loud AGNs. The photon index of the X-ray continuum (8 keV−20 keV) generated in such an electron shower is 1 ≤ Γ ≤ 2. Γ and the continuum strength are strongly model-dependent; they are dependent on both the relative orientation between the electron beam and the observer and the radius of the electron beam compared with the characteristic radius of the absorbing medium. The relevance of particle energy transport compared to photon energy transport in the AGN environment is outlined.Peer reviewe

Seguimiento de estudiantes y egresados en los Dobles Grados de Matemáticas

El proyecto tiene carácter interfacultativo e incluye a las facultades de CC. Económicas y Empresariales, Ciencias Físicas, Informática y Ciencias Matemáticas. Es una continuación natural del PIMCD-287 “Elaboración de estudios para el seguimiento del rendimiento académico de los estudiantes de los dobles grados en Matemáticas”. El objetivo global del proyecto ha consistido en el de avanzar en el trabajo iniciado con el proyecto anterior concedido en el curso 2014-15 y profundizar en el análisis de las distintas acciones que se han llevado a cabo a través de las encuestas realizadas al alumnado, reuniones y el debate sobre aprendizaje/evaluación continua en Grados y dobles Grados. Se continuó con la revisión del modelo de coordinación horizontal académico-docente, con el fin de dotarlo de una mayor eficacia

Pretectal neurons control hunting behaviour

For many species, hunting is an innate behaviour that is crucial for survival, yet the circuits that control predatory action sequences are poorly understood. We used larval zebrafish to identify a population of pretectal neurons that control hunting. By combining calcium imaging with a virtual hunting assay, we identified a discrete pretectal region that is selectively active when animals initiate hunting. Targeted genetic labelling allowed us to examine the function and morphology of individual cells and identify two classes of pretectal neuron that project to ipsilateral optic tectum or the contralateral tegmentum. Optogenetic stimulation of single neurons of either class was able to induce sustained hunting sequences, in the absence of prey. Furthermore, laser ablation of these neurons impaired prey-catching and prevented induction of hunting by optogenetic stimulation of the anterior-ventral tectum. We propose that this specific population of pretectal neurons functions as a command system to induce predatory behaviour