Recent Talks

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.

Pandas is an open source Python package that is widely used for data analysis. It is a powerful ally for data munging/wrangling and databases manipulation/visualisation, and a must-have tool for Data Scientists. In this seminar we will have a general overview on its functionality and we will run over some of the reasons of its large success in the Data Science community.

Gaia has provided distances and photometry, and thus colour-magnitude diagrams in the absolute plane, for stars over a large volume in the Milky Way, encompassing significant fractions of the thin and thick disk, and halo. This has allowed us, for the first time, to derive unprecedentedly detailed star formation histories from direct modelling of these colour-magnitude diagrams, using the same techniques that have been proven successful for external galaxies in the Local Group. Our first results for a volume of 2 Kpc radius from the Sun are extraordinarily promising. Applied to inner halo stars selected kinematically using Gaia proper motions, this technique has allowed us to date the merger of Gaia-Enceladus, to characterise the age profile of the accreted stars and of those present in the Milky Way at the time of the merger, and to detect a conspicuous burst of star formation in the thick disk occurred at the time of the merger (Gallart+2019). We have also obtained a representative SFH for the Galactic disk, which clearly shows the presence of up to four epochs of enhanced star formation well constrained in time, that can be associated with various pericentric passages of the Sgr dwarf galaxy (Ruiz-Lara+2020). Additionally, we are obtaining results of unprecedented clarity regarding the vertical distribution of ages and metallicities in the Milky Way disk. I will discuss these results as well as future prospects to reach a larger Milky Way volume, and to combine chemodynamical information from spectroscopic surveys with this new approach to study the Milky Way evolutionary history.