Últimas charlas

Metal-poor stars play a key role in understanding the nucleosynthesis of heavy elements in the early Universe, as their chemical abundances reflect the composition of the gas in which they formed. High-resolution spectroscopic studies show that very metal-poor stars exhibit a wide spread in the abundances of neutron-capture elements. This large star-to-star scatter seems to suggest that that multiple astrophysical sites contributed to their production, operating under different physical conditions. The nucleosynthesis processes and formation sites responsible for the production of neutron-capture elements in the early Galaxy are still a matter of debate, as several processes could be involved (e.g. s- process, r- process, i-process, weak r-process, weak s-process, ...). To trace the formation and evolution of heavy elements in the Milky Way we need detailed chemical abundances for a large sample of metal-poor ([Fe/H]<-1) stars, in order to compare them with the predictions of theoretical models. In this talk, I will present recent results from two projects, CERES and MINCE, which aim to characterise the nucleosynthesis and Galactic chemical evolution of heavy elements, and future work within the OUTLIERS project in IAC.

The inflow of accretion in active galactic nuclei (AGN) and subsequent outflow are ultimately related to the feedback processes that link galaxy and black hole growth. New capabilities, especially JWST and ALMA, probe the scales where feedback is initiated. They reveal the multi-phase AGN environment that produces emission and obscures the activity of the central engine. Even nearby samples show evolution, distinguishing a phase of building up the AGN from one where outflow dominates and dusty winds can appear. Numerical radiative transfer models that aim to account for the resulting observations must be augmented to include a wider range of physical properties in these environments.

The atmosphere has a turbulent which produces aberrations on the wavefront of what otherwise would be a point source of laser light in the case of free-space optical communications, as well as it is the case for starlight when a telescope is pointed at a distant star. This problem is of special relevance in the arise of extremely large telescopes, as a bigger aperture encompasses the collection of more patches of an already turbulent atmosphere. Therefore, innovative adaptive optic techniques must be applied in order to exploit the outstanding resolution that can be achieved only at the diffraction limit of telescopes such as GTC, TMT, or ELT.

In this talk we present results incoming from applying Spatial Light Modulators (SLM) as the core element both for sensing and correcting the wavefront distortions. Instead of the common approach, which involves the use of Deformable Mirrors (DM), we make use of liquid-crystal-on-silicon (LCOS) SLM's, which can digitally modify the refractive index of each of the nearly half a million pixels it possess. In the sensing aspect we implement the novel Diffractive Wavefront Sensor (DWS) that can produce a wavefront directly from the image obtained after placing a diffractive element in the focal plane. Experimental results indicate robustness against obscurations and diffraction (caused by segmented mirrors and structures ubiquitous in large telescopes), and a spatial resolution orders of magnitude higher that the well known Shack-Hartman sensor.

Massive early-type galaxies (ETGs) represent the final stages of galaxy evolution in the hierarchical formation framework. They typically host central supermassive black holes (SMBHs), which co-evolve with their galaxies and provide an excellent opportunity to investigate the linked growth of BHs and ETGs. Using integral-field spectroscopic data (MUSE, SINFONI) and triaxial Schwarzschild orbit-based modelling, we investigate the BH masses and stellar orbital structures of four massive ETGs. Our models incorporate radially varying stellar mass-to-light ratios, driven by gradients in the initial mass function (IMF). From stellar population modelling, we detect super-Salpeter IMFs in galaxy centers and find that IMF variations can alter BH mass estimates by 10–30% relative to constant-IMF assumptions. In this talk, I will present results on the stellar populations and SMBHs of our modelled ETGs, showing how they are linked. In addition, I will also discuss how different orbital families shape the observed kinematics, reveal the assembly histories of ETGs, and reflect the influence of central SMBHs.

En esta charla se mostrará el trabajo de los compañeros del IAC que fueron a Borobia para ver, fotografiar y retransmitir el eclipse, a parte de dar charlas y colaborar en las actividades realizadas por el observatorio de Borobia. ¿Qué tal ha sido la experiencia del primer eclipse total de este singular grupito?

LiteBIRD is the next-generation CMB space mission designed to produce full-sky polarization maps with unprecedented sensitivity. Spain contributes to the scientific exploitation, to the data-processing centres that will support operations and analysis to the mission, and to the technological development of the payload through the Temperature Monitoring and Compensation System (TMCS). The TMCS is responsible for monitoring the instrument’s thermal environment, with particular focus on the sub-kelvin cryogenic stage that sets the operating temperature of the Transition Edge Sensor (TES) detectors. This stage operates near 100 mK, where the scientific requirements impose thermal stability at the level of a few micro-kelvin—or even fractions of a micro-kelvin—over the relevant time scales (<0.1uHz - 5Hz). Achieving such performance, while potentially compensating for temperature fluctuations induced by cosmic-ray impacts and sky-background variations on the focal plane, constitutes a major technical challenge. The ongoing prototyping activities are therefore centred on identifying the critical functions of the TMCS electronics, developing dedicated electronic designs for each of them, and validating their feasibility through targeted tests. A first complete readout chain has been implemented to characterise components, evaluate noise and stability performance, verify subsystem functionality, and determine the architectural refinements required for the next design iteration. This presentation will summarise the thermal and stability requirements of the LiteBIRD instrument, describe the architecture and expected performance of the TMCS readout electronics, and present the results obtained during the current validation campaign. Finally, the status and needs of the room-temperature and sub-kelvin test benches, as well as the key development activities planned for the coming months, will be outlined.

Oscillations of solar-like stars are thought to be stochastically excited, and following Lighthill, the primary excitation mechanism is often assumed to be quadrupolar turbulent Reynolds stresses, though other models for excitation have been proposed. Recently, techniques have been developed to measure the near field wavefronts emitted by individual solar acoustic sources. These techniques have been successfully applied to radiative magnetohydrodynamic simulations of the upper solar convection zone and lower solar atmosphere, and direct waveform fitting has been used to invert for the source properties. Efforts to extend these measurements to high spatial resolution, high temporal cadence solar observations are underway. In this talk we will summarize what the global p-mode spectrum suggests about the stochastic excitation of the solar acoustic oscillations, describe what we have learned about the excitation of acoustic waves recently from the numerical simulations, and outline an observational path to similar success with the real Sun.

Una de las principales limitaciones tanto del sistema LGS como de sus componentes es evitar las frecuencias propias que pudieran afectar al espejo primario de GTC, empeorando sus prestaciones. El objetivo de la presente charla es presentar los estudios analíticos, FEMs y resultados experimentales para las frecuencias propias del Banco Óptico del Sistema de Transferencia de la Estrella Guía Láser para GTC. Se hará hincapié en la cualificación de modelos de elementos finitos, así como una demostración práctica de las complicaciones que presenta el estudio dinámico de los sistemas.