Recent Talks

We will introduce several ways in which trivially embarrassingly parallel tasks can be run in laptops and desktops. We will introduce command-line tools such as GNU parallel and Kiko. We will then focus on simple techniques for optimisation of scientific computations in python. We will cover parallel computing with multiprocessing, acceleration of functions via numba, and GPU computing with cupy. The goal is to provide an easy roadmap for python code optimisation methods that can applied on already existing code, without writing a single line of C or FORTRAN.

In the aftermath of the cataclysmic explosion of massive stars, a vast zoology of source type is observed such as Supernova Remnants (SNRs), pulsar wind nebulae, pulsars and ‘zombie’ pulsars. Due to high velocity shock-waves combined with a high magnetic field or fast rotation in the case of pulsars, an efficient particle acceleration is achieved in those objects which are believed to be significant contributors to the pool of Galactic cosmic rays.
This seminar will start with a short introduction on particle acceleration and SNR physics, present the current scientific questions, and what we’ve learned from high-energy observations in the recent years.

On a more technical note, I will also present a new analysis method to fully exploit the multi-dimensional (X, Y, Energy) nature of X-ray data. This blind source separation method draws from the most advanced signal processing techniques to capture and disentangle the wealth of information contained in deep archival observations.

Zoom: 
https://rediris.zoom.us/j/86212537380?pwd=MGdYSE1rVDAyVlVESFE5RWEwOVlqZz09
Meeting ID: 862 1253 7380Passcode: 431670

YouTube: https://youtu.be/YwuCrGmp9_w

The phenomenon of magnetic reconnection in a magnetized plasma has been a subject of numerous studies over the past several decades in a variety of contexts, from high energy astrophysics, to solar and space physics, to laboratory-based experiments.  However, most magnetic reconnection studies have been devoted to exploring different collisionality regimes in a fully ionized single specie plasma.  Until recently, the physics of magnetic reconnection in partially, and weakly, ionized plasmas has received relatively little attention.  In this talk, I will provide a brief overview of the physical effects that partial ionization of the ambient medium may introduce in the dynamics of magnetic reconnection, with a particular focus on the environment of the lower solar atmosphere.

During the past 50 years, we have witnessed humankind’s first good, detailed look at the planets in our known Solar System.  All of these advances built upon Earth-based telescopic observations.  We predict surface conditions on other Solar System bodies before spacecraft reach them for in situ study.  The dominant type of asteroid identified telescopically in the main asteroid belt is classed as a C-complex asteroid, likely the origin of many of the primitive carbonaceous chondrite meteorites.

In the visible spectral region, one prominent, identifying spectral feature indicating the presence of Fe2+ → Fe3+ in clay minerals is located near 0.7 µm in over half of the C-complex asteroids.  Using its spectral presence, we can constrain the presence and thermal history of these objects in the Solar System.  I will describe the feature, and the implications of the evidence of its presence.  As an illustration, I will then show how we can use the presence of this feature to probe Solar System developmental history through examining the spectra of the jovian outer irregular satellites.

La experiencia en la compensación de los efectos de la turbulencia atmosférica le permitió al IAC desarrollar el sistema de control de la OGS y demostrar las comunicaciones ópticas entre satélites y tierra, poniendo a la ESA por delante de la NASA en este campo. Gracias a esto, el IAC consiguió contratos de la ESA en competencia abierta relacionados con las comunicaciones ópticas en el espacio. Pero España no participa en el nuevo programa de la ESA para financiar estas actividades, impidiendo al IAC presentarse a nuevos contratos. No obstante, la financiación conseguida de los fondos de recuperación para comunicaciones ópticas en el espacio nos está permitiendo mantener actividades.

En paralelo, aprovechando el desarrollo de la OGS, el IAC empezó a realizar experimentos de estrellas guía láser (LGS) de Na para óptica adaptativa, con el objetivo final de desarrollar la LGS para GTC. Posteriormente se firmó un acuerdo con ESO para realizar experimentos en el OT y ORM con la última tecnología de láseres de Na, tecnología que ha hecho viable lanzar el proyecto de LGS para GTC, dentro del principal programa actual en el Área de Instrumentación. La renovación del acuerdo con la ESO nos está permitiendo participar en nuevos experimentos que aplican la LGS en las comunicaciones ópticas en el espacio

The light emitted by all galaxies across the history of the Universe is encoded in the intensity of the extragalactic background light (EBL), the diffuse cosmic radiation field at ultraviolet, optical, and infrared wavelengths. The EBL is a source of opacity for very high energy gamma rays via pair production, leaving a characteristic attenuation imprint in the spectra of distant gamma-ray sources. In this seminar, I will report on new measurements of the EBL using gamma-ray data from both the Large Area Telescope on board the Fermi Gamma-ray Space Telescope and ground-based Imaging Atmospheric Cherenkov Telescopes. These unprecedented measurements have allowed us to derive the cosmic star-formation history, the number density of faint galaxies during the re-ionization epoch, and also the expansion rate of the Universe and its matter content. These results demonstrate that gamma-ray astrophysics has matured to the point of providing competitive measurements of cosmic properties previously restricted to techniques used by more traditional astronomy.

Las comunicaciones ópticas en el espacio libre presentan un gran atractivo de cara al futuro por las distintas ventajas que introducen respecto a los métodos de comunicación tradicionales entre la tierra y el espacio (satélites). En este contexto, el acoplamiento de un haz láser en una fibra óptica es uno de los puntos más importantes a tener en cuenta en el desarrollo de esta tecnología.

El objetivo de esta charla es dar cuenta del trabajo que se está realizando en el IAC para el estudio del rendimiento existente en dicho acoplamiento, así como los resultados que se espera obtener. Se pone especial interés en su variación debido a fenómenos atmosféricos y a la necesidad de usar óptica adaptativa para corregir el rendimiento. Este trabajo se enmarca dentro de la beca de verano ofrecida por el grupo de investigación en comunicaciones ópticas en el espacio libre (FSOC, por sus siglas en inglés), dentro del área de instrumentación del IAC.

The Epoch of Reionization (EoR) was the last major phase transition of the Universe. While the timeline of reionization is increasingly well-constrained, its sources remain elusive. Due to their number density, star-forming galaxies are the likeliest candidates, but whether the ionizing photon budget arose from a multitude of ultra-faint galaxies or a rarer set of bright galaxies is a key open question. The key uncertainty is the ionizing photon escape fraction (LyC Fesc), and how this varies among galaxy properties. In my talk I will argue to tackle this problem based on measurements of resolved Lyman-alpha (LyA) emission from the X-SHOOTER LyA survey at z=2 (XLS-z2). I will show observational evidence that the defining traits of LyC leaking galaxies are highly ionising stellar populations, low column density gas and a dust-free, high ionization state ISM. This is evidence that galaxies leak ionising photons (with LyC Fesc 20-50 %) when the hottest stars are still shining. Motivated by these results, I will present a model of a LyA Emitter-dominated emissivity that explains the relative flatness of the total galaxy emissivity over z~2-8 and the reionization of the Universe by z~6 under reasonable assumptions, thus naturally accounting for the strong evolution of the average LyC Fesc of the full galaxy population between redshifts z~2-8. In a fiducial choice of model parameters, the "disco" emissivity is dominated by a strong minority of galaxies with intermediate mass (~10^{^8} Msun). I will conclude with proposed observational tests to further develop the LyA-anchored formalism. 

Zoom link: 
https://rediris.zoom.us/j/85785567444?pwd=ckNnYzMyQk9WRHI0MFRROWJ1QnJWdz09
Meeting ID: 857 8556 7444

Passcode: 058978

YouTube: https://youtu.be/iNmNi-bTKtM

El objetivo de esta charla es poner en conocimiento del personal del IAC el estado y perspectivas a medio plazo de IACTEC. La charla está orientada a informarles de aspectos útiles a quienes trabajan en otras sedes y proyectos del IAC, con la intención de acercarles a los recursos (infraestructura) y sinergias (proyectos) disponibles. Les esperamos y animamos a asistir y participar.