Colloquia
Talks given by high profile astronomers and scientists.
Abstract
La Astronomía, quizá la ciencia organizada más antigua, presente en todas las culturas, que en este Siglo XXI es fundamentalmente Astrofísica, intenta penetrar en el conocimiento de la naturaleza y evolución del Universo, en su conjunto y en detalle. En tan desmesurada aventura, la clave para avanzar sigue siendo la observación astronómica. Y Canarias ha tenido la suerte de que la atmosfera de sus cumbres posea condiciones excepcionales para la observación astronómica. Por eso los observatorios del Instituto de Astrofísica de Canarias (IAC) reúnen la batería más completa de telescopios. Estos observatorios de Canarias constituyen una reserva astronómica mundial, protegida por ley, donde tienen telescopios e instrumentos más sesenta instituciones de dieciocho países. En el Observatorio del Roque de los Muchachos, además, acaba de entrar en operación el Gran Telescopio Canarias, construido por España. Siendo, con sus 10.4 m. de apertura, el mayor y más avanzado telescopio óptico-infrarrojo del momento. Pronto, esperamos, que a él también venga el Telescopio Europeo Extremadamente Grande (E-ELT) de 42 m., haciendo de en nuestras Islas el centro de gravedad de esta rama de la Ciencia.
La Astrofísica demanda la última tecnología para sus instrumentos en tierra y espacio. Por eso es germen de desarrollo tecnológico e industrial. Lo que supone riqueza económica y social. Sin dejar de ser por ello, como toda ciencia básica, fuente de cultura, al tratar de dar respuestas a las preguntas fundamentales del ser humano, y dotarle de nuevas cosmovisiones.
Abstract
The study of the Milky is expected to have a major impact on our understanding of how galaxies form and evolve. "Near-field cosmology" is being vigorously pursued through a series of major surveys of the Galaxy's stellar content (2-MASS, SDSS, RAVE, Hermes, Apogee, Gaia) that are either in hand or pending. It will be argued that what we want to know is deeply buried in these data and can only be extracted by comparing the surveys with a hierarchy of dynamical models of ever increasing complexity. Work currently being done to build such hierarchical models will be described, and some early results from this work will be summarised.
Abstract
There is a "Warped side" of our universe, consisting of objects and phenomena that are made solely or largely from warped spacetime. Examples are black holes, singularities (inside black holes and in the big bang), and cosmic strings. Numerical-relativity simulations are revolutionizing our understanding of what could exist on our universe's Warped Side; and gravitational-wave observations (LIGO, VIRGO, LISA, ...) will reveal what phenomena actually do exist on the Warped Side, and how they behave.
Abstract
Over the next decade or so, the gravitational-wave window onto the Universe will be opened in four frequency bands that span 22 orders of magnitude: The high-frequency band, 10 to 10,000 Hz (ground-based interferometers such as LIGO and VIRGO), the low-frequency band, 10-5 to 0.1 Hz (the space-based interferometer LISA), the very-low frequency band, 10-9 to 10-7 Hz (pulsar timing arrays), and the extremely-low-frequency band, 10-18 to 10-16 Hz (polarization of the cosmic microwave background). This lecture will describe these four bands, the detectors that are being developed to explore them, and what we are likely to learn about black holes, neutron stars, white dwarfs and early-universe exotica from these detectors' observations.
Abstract
Spectroscopic observations of novae date back a century, and the fundamental nature of the outburst has been understood for 50 years. Yet, recent observations suggest possible major modifications to the standard nova paradigm. A high-resolution spectroscopic survey of novae has revealed short-lived heavy element absorption systems near maximum light consisting of Fe-peak and s-process elements. The absorbing gas is circumbinary and it must pre-exist the outburst. Its origin appears to be mass ejection from the secondary star, implying large episodic mass transfer events from the secondary that initiate the nova outburst. The spectroscopic evolution of novae is interpreted in terms of two distinct interacting gas systems in which the bright continuum is produced by the outburst ejecta but absorption and emission lines originate in gas ejected by the secondary star in a way that may explain dust formation and X-ray emission from novae.
Abstract
I will present grid-adaptive computational studies of both magnetized and unmagnetized jet flows, with significantly relativistic bulk speeds, as appropriate for AGN jets. Our relativistic jet studies shed light on the observationally established classification of Fanaroff-Riley galaxies, where the appearance in radio maps distinguishes two types of jet morphologies. We investigate how density changes in the external medium can induce one-sided jet decelerations, explaining the existence of hybrid morphology radio sources. Our simulations explore under which conditions highly energetic FR II jets may suddenly decelerate and continue with FR I characteristics. In a related investigation, we explore the role of dynamically important, organized magnetic fields in the collimation of the relativistic jet flows. In that study, we concentrate on morphological features of the bow shock and the jet beam, for various jet Lorentz factors and magnetic field helicities. We show that the helicity of the magnetic field is effectively transported down the beam, with compression zones in between diagonal internal cross-shocks showing stronger toroidal field regions. For the high speed jets considered, significant jet deceleration only occurs beyond distances exceeding hundred jet radii, as the axial flow can reaccelerate downstream to internal cross-shocks. This reacceleration is magnetically aided, due to field compression across the internal shocks which pinch the flow.
Abstract
For a long time radiative MHD simulations of entire sunspots from first principles were out of reach due to insufficient computing resources. Over the past 4 years simulations have evolved from 6x6x2 Mm size domains focusing on the details of umbral dots to simulations covering a pair of opposite polarity sunspots in a 100x50x6 Mm domain. In this talk I will discuss the numerical challenges encountered in comprehensive radiative MHD simulations of active regions and summarize the recent progress. Numerical simulations point toward a common magnetoconvective origin of umbral dots and filaments in the inner and outer penumbra. Most recent simulations also capture the processes involved in the formation of an extended outer penumbra with strong horizontal outflows averaging around 5 km/s in the photosphere. I will discuss in detail the magneto convective origin of penumbral fine structure as well as the Evershed flow. I will conclude with a brief summary of recent helioseismic studies based on realistic MHD simulations as well as inferences on the sub surface structure of sunspots.
Abstract
New results on the antiproton-to-proton and positron-to-all electron ratios over a wide energy range (1 – 100 GeV) have been obtained by the PAMELA mission. These data are mainly interpreted in terms of dark matter annihilation or pulsar contribution. The instrument PAMELA, in orbit since June 15th, 2006 on board the Russian satellite Resurs DK1, is daily delivering to ground 16 Gigabytes of data. The apparatus is designed to study charged particles in the cosmic radiation, with a particular focus on antiparticles for searching antimatter and signals of dark matter annihilation. A combination of a magnetic spectrometer and different detectors allows antiparticles to be reliably identified from a large background of other charged particles. The talk will illustrate the most important scientific results obtained by PAMELA, together with some of the more recent theoretical interpretations.
Abstract
AEGIS (All-wavelength Extended Groth strip International Survey: aegis.ucolick.org) is on-going survey that opens up new views of the development of galaxies and AGN's at redshifts z about 1. AEGIS is panchromatic like GOODS, with coverage ranging from X-ray to radio, and nearly as deep but more panoramic by covering a 4x larger region. Its backbone is the most Northern (accessible to the GTC) of the four fields of the DEEP2 Keck spectroscopic survey, which provides not only precision redshifts that yield reliable pairs, groups, and environments, but also internal kinematics and chemical abundances. After an overview of the DEEP and AEGIS surveys, I will share some recent highlights, including using a new kinematic measure for distant galaxies to track Tully-Fisher-like evolution; discovering metal poor, massive, luminous galaxies; finding ubiquitous galactic gas outflows among distant star forming galaxies; and exploring the nature of distant x-ray AGNs.
Abstract
The SAURON survey has revised our view of early type galaxies discovering that central disks and multiple kinematic components are common; 75% of the sample have extended ionized gas, often misaligned with the stars; half of S0s and 25% of Es have intermediate age populations. There is a tight relationship between the escape velocity and Mg line strength which holds both within and between galaxies raising uncomfortable questions for hierarchical assembly. Many of the properties of ETGs are related to a measure of their specific angular momentum : slow rotators are triaxial, close to spherical, isotropic and frequently exhibit decoupled central kinematics, whereas fast rotators are intrinsically flatter, oblate, have disk-like (anisotropic) kinematics and often have Mg enhanced disks. In general the slow rotators are more massive and have older populations Only half of the elliptical galaxies exhibit slow rotation, the remainder have stellar disks showing that the historic division by morphological class is physically misleading. We suggest that the contrasting physical properties of fast and slow rotators arise through distinct assembly histories with slow rotators forming in gas free, dry mergers and fast rotators retaining a disk component through a dissipative merger.Upcoming talks
- Deep Learning for Full-Event Reconstruction in Imaging Atmospheric Cherenkov Telescopes: The CTLearn PackageWednesday June 4, 2025 - 10:30 GMT+1 (Aula)
- FPGAs en instrumentación espacial para espectropolarimetría solarDavid Hernández ExpósitoFriday June 13, 2025 - 10:30 GMT+1 (Aula)
Recent Colloquia
Recent Talks
