Recent Talks

At present, our understanding of the formation history of the MW is limited due to the complexity of observing the imprints of accretion events and of reproducing them in numerical simulations. Moreover, though being the only galaxy, in which the Galactic potential can be probed in detail, the distribution of mass in the MW, and hence of the dark matter, is poorly constraint, especially at large distances. In addition, the MW is not isolated, and it has recently been suggested that the infall of the LMC can induce a perturbation in the stellar and dark matter distribution of the MW. As a consequence, the details of the formation history of our Galaxy are still unknown, such as the number of accretion events, the mass of the accreted galaxies, and the epoch of these events. Yet this information is crucial to understand our environment and to constrain the theoretical models and simulations that try to reproduce it.

One of the major challenges of the field is that a tremendous number of multi-aspect (astrometric, photometric and spectroscopic) observations at significant depth is required to study the morphology, the kinematics and the chemistry of the outskirts of our Galaxy, where are located the signatures of these events. Hopefully, the advent of recent and incoming complementary large surveys, such as the European Gaia mission, UNIONS (Ultraviolet Near Infrared Optical Northern Survey), Pristine, Pan-STARRS (PS), WEAVE or LSST (Legacy Survey of Space and Time), is offering a new global point of view on our Galaxy’s halo, allowing us to precisely probe the Galactic potential our the MW, and to retrace itsaccretion history.

In this talk I will present recent works that have been conducted to better catarerized our Galaxy and its history with some of the existing surveys mentioned above. In addition, I will present the major improvement that will bring this new generation of large, multi-aspect surveys, to study both our Galactic history, as well as the fundamental nature of the dark matter.

(This seminar is organized by the IAU G5 commission on stellar and planetary atmospheres) 

Task-based computing is a method where computational problems are split
   into a large number of semi-independent tasks (cf.
   2018MNRAS.477..624N). The method is a general one, with application not
   limited to traditional grid-based simulations; it can be applied with
   advantages also to particle-based and hybrid simulations, which involve
   both particles and fields. The main advantages emerge when doing
   simulations of very complex and / or multi-scale systems, where the
   cost of updating is very unevenly distributed in space, with perhaps
   large volumes with very low update cost and small but important regions
   with large update costs.

   Possible applications in the context of stellar atmospheres include
   modelling that covers large scales, such as whole active regions on the
   Sun or even the entire Sun, while at the same time allows resolving
   small-scale details in the photosphere, chromosphere, and corona. In
   the context of planetary atmospheres, models of pebble-accreting hot
   primordial atmospheres that cover all scales, from the surfaces of
   Mars- and Earth-size embryos to the scale heights of the surrounding
   protoplanetary disks, have already been computed (2018MNRAS.479.5136P,
   2019MNRAS.482L.107P), and one can envision a number of applications
   where the task-based computing advantage is leveraged, for example to
   selectively do the detailed chemistry necessary to treat atmospheres
   saturated with evaporated solids, or to do complex cloud chemistry
   combined with 3-D radiative transfer.

   In the talk I will give a quick overview of the principles behind
   task-based computing, and then use both already published and still
   on-going work to illustrate how this may be used in practice. I will
   finish by discussing how these methods could be applied with great
   advantage to problems such as non-equilibrium ionization, non-LTE
   radiative transfer, and partial redistribution diagnostics of spectral
   lines.

The AO system of the 10-m class Gran Telescopio Canarias is in its final test phase in the lab at the Instituto de Astrofísica de Canarias. It has to successfully pass all the system tests to carry out the factory acceptance and be shipped to Roque de Los Muchachos Observatory (ORM) in 2021. Designed to be a facility, robustness and operability are two of its key characteristics. A series of calibrations are required and methodically run to achieve its ultimate performance.
I will detail in this talk the full characterization of the system, allowing to verify the compliance with the specifications and paving the way towards shipping the system to ORM.

Unirse a la reunión Zoom
https://rediris.zoom.us/j/88097037502?pwd=eWY0eWx4QzRFN2U4Q0wyZVk2ODc1UT09

ID de reunión: 880 9703 7502
Código de acceso: 392830

Enlace Youtube: https://youtu.be/_B9IrBfjwCc

Bosonic ultra-light dark matter (ULDM) in the mass range m ~ $10^{-22} - 10^{-21} \rm eV$ has been invoked as a motivated candidate with new input for the small-scale `puzzles' of cold dark matter. Numerical simulations show that these models form cored density distributions at the center of galaxies ('solitons'). These works also found an empirical scaling relation between the mass of the large-scale host halo and the mass of the central soliton. We show that this relation predicts that the peak circular velocity of the outskirts of the galaxy should approximately repeat itself in the central region. Contrasting this prediction to the measured rotation curves of well-resolved near-by galaxies, we show that ULDM in the mass range m ~ $10^{-22} - 10^{-21} \rm eV$ is in tension with the data.

Cosmological and astrophysical experimental data demark a large share of the limits of our knowledge in fundamental physics. I'll review two pieces of evidence of our ignorance: the nature of dark matter and the generation of baryon asymmetry in the universe, together with some of the proposed solutions to each. Finally, a novel connection between the two open problems will be presented.

El propósito de esta charla es comentar una serie de aspectos y detalles del día a día en la gestión de proyectos que quizás no sean tan del dominio público como el clásico control del alcance, coste y tiempos en el ámbito de un proyecto. Aparte de las tareas y herramientas específicas para el seguimiento de las actividades dentro de un proyecto, que implican el manejo de múltiples tablas y documentación, con paquetes de trabajo, definición de tareas, distribución de un árbol de producto, listado de requerimientos, tablas de presupuestos, listado de entregables, etc., el día a día de la gestión implica una serie de trámites, procesos y acciones de todo tipo, grandes y pequeñas, que, poco a poco, van sumando su granito de arena a la montaña sobre la que se asienta el progreso diario de un proyecto.

The "Asteroid Terrestrial-impact Last Alert System" (ATLAS) is funded by NASA to find dangerous asteroids before they strike the Earth. It has operated from two Hawaii sites since 2015 and will very soon have South Africa and Chile sites to cover the entire visible sky every night four times to a limiting magnitude of m~19.5 per exposure. The process of finding asteroids leads to auxiliary data products along the way including accurate photometry of all stars in the sky and detection of flares and transients.  I will describe ATLAS, how we approach our NASA mission to find NEOs, how ATLAS fits in with other ongoing or planned surveys, some of the data products that are available now, and the many new scientific opportunities that are emerging and waiting to be exploited.  Time will be reserved at the end of the talk for some real time demonstrations: audience participation is encouraged.  References include 2018PASP..130f4505T, our public web page at fallingstar.com and fallingstar.com/weather/ to see our current fisheye and webcam views at all four sites.

Zoom link: https://rediris.zoom.us/j/82241288569?pwd=QmtUWkNoRHNvYlk3dWJhRCtCdE1RQT0

Meeting ID: 822 4128 8569
Passcode: 776606

Youtube: https://youtu.be/Ax-70hAibow

A solar flare involves the conversion of magnetic energy stored in the coronal magnetic field into the kinetic energy of thermal and non-thermal particles, mass motion, and radiation. How this happens remains a central question in solar physics. A particular long-standing puzzle is how such a high fraction of the stored magnetic energy - up to a half - arrives in the kinetic energy of accelerated non-thermal particles. In this talk I will present an observational overview of solar flares with an emphasis on accelerated particles, discuss some ideas and constraints on particle acceleration, and present some new observations of the possible role of plasma turbulence in the acceleration process.

Planes originales de software de control, en que ha quedado y que se esta realizando finalmente

The expansion of the Universe is in an accelerated phase. This
acceleration was first estabilished by observations of SuperNovae, and
has since been confirmed through a range of independent observations.

The physical cause of this acceleration is coined Dark Energy, and
most observations indicate that Einsteins cosmological constant
provides a very good fit. In that case, approximately 70% of the
energy of the Universe presently consists of this cosmological
constant.

I will in this talk address the possibility that there may exist other
possible causes of the observed acceleration. In particular will I
discuss a concrete model, inspired by the well-known Lorentz force in
electromagnetism, where Dark Matter causes the acceleration.  With a
fairly simple numerical simulation we find that the model appears
consistent with all observations.

In such a model, where Dark Matter properties causes the acceleration
of the Universe, there is no need for a cosmological constant.