Recent Talks

List of all the talks in the archive, sorted by date.


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Tuesday May 2, 2023
Dr. Carlos Quintero Noda
IAC

Abstract

We divide this talk into two parts. In the first part, we will introduce the numerical codes we use, mainly in solar physics, to infer information about the solar atmosphere from spectro-polarimetric observations. In particular, we will present a new version that was recently developed (see Ruiz Cobo et al., 2022). In the second part of the talk, we will learn how we opted to bring the code to the public through online tutorials, and we will show where to find them (see the link below). Also, we will explain why we believe this new approach could be interesting for other research areas and give some tips in case someone is interested in trying the method.


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Thursday April 27, 2023
Dr. Emma Fernandez Alvar
IAC

Abstract

The previous years have witnessed a big leap forward in our understanding of the Milky Way. Thanks to the highly accurate astrometry and photometry provided by the Gaia mission in combination with large photometric and spectroscopic all-sky surveys, we have now a clearer view of the chemo-dynamics of the stellar populations that constitute our Galaxy. Our former characterization of the Milky Way components (the bulge, halo, and thick and thin discs) is now compromised by the latest discoveries and their limits are blurrier than ever. However, hints on the kind of events and processes that led to the formation of our Galaxy emerge from the analysis of these high-quality data. In this talk I will review the latest results about what caused the current stellar halo configuration and the observational evidences of the dawn of the Milky Way’s disc. I will also present the project carried out at the ULL/IAC to derive the star formation history of the Milky Way which will provide the temporal information that is still missing in Galactic research.

 

 

 

https://rediris.zoom.us/j/85737198942?pwd=dG1lYmNVRjR3dzRGZFhldUhGRloyUT09
ID de reunión: 857 3719 8942

Código de acceso: 350472

https://youtube.com/live/i1KS2YngkMA?feature=share


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Tuesday April 25, 2023
Dr. Claudia Raiteri
INAF-Osservatorio Astrofisico di Torino

Abstract

Active galactic nuclei (AGN) are the most luminous persistent sources in the universe. A minority of AGN are characterised by powerful plasma jets extending from close to the supermassive black hole at the centre of their host galaxy up to megaparsec scales in the intergalactic space. Inside these jets, charged particles are accelerated to relativistic speeds and emit non-thermal radiation. In blazars one jet is oriented at a small angle with respect to the line of sight, and this causes Doppler beaming of the jet emission, with consequent flux enhancement, and decrease of the variability time scales. The dominant contribution of the jet radiation to the blazar emission makes these objects ideal sources to investigate what happens in the inner regions of AGN jets and even what is the jet structure and dynamics. We have been studying blazar variability for more than 20 years in the framework of the Whole Blazar Telescope (WEBT) Collaboration, including many tens of astronomers observing mainly in the optical, but also in the radio and near-infrared bands. The analysis of the wealth of multiwavelength data gathered during the WEBT monitoring campaigns, with unique time resolution in the optical band, allowed us to outline a model for the blazar variability, involving an inhomogeneous twisting jet. In the final part of the seminar we will mention the contribution to blazar understanding that is expected from Vera C. Rubin Observatory’s Legacy Survey of Space and Time.


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Friday April 21, 2023
Alfonso Ynigo Rivera
IAC

Abstract

 A lo largo del último año, el equipo de IACTEC-Espacio ha implementado la ingeniería basada en modelos (MBSE de sus siglas en inglés) progresivamente en todos sus desarrollos. Esta metodología tiene como objetivo último la utilización de modelos que representen un repositorio de información única y fidedigna en los desarrollos de ingeniería. La herramienta utilizada permite definir la estructura de producto, los requisitos a nivel de sistema y a niveles inferiores y el proceso de verificación de los mismos, así como la realización de análisis basados en las variables del modelo y la gestión de tareas del equipo. En la charla se mostrará cómo se ha implementado la ingeniería basada en modelos en el desarrollo de DRAGO-2 y de VINIS, resaltando las ventajas y limitaciones de esta metodología.


Unirse a la reunión Zoom:

https://rediris.zoom.us/j/89547725277
ID de reunión:895 4772 5277

 

Youtube:

https://youtube.com/live/TLAdIVSs0l4?feature=share


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Thursday April 20, 2023
Dr. Eva Laplace
HITS, Heidelberg

Abstract

Gravitational-wave observations have revealed the population of stellar remnants from a new angle. Yet their stellar progenitors remain uncertain, in particular in the case of black holes. At least a fraction of these progenitors is believed to form in isolated binary systems. In this talk, I will discuss how binary mass transfer affects the late evolution and final fate of massive stars. The focus will be on stars that transfer their outer layers to a companion star and become binary-stripped. Binary-stripped stars develop systematically different core structures compared to single stars. I will discuss consequences for supernova progenitors, black hole formation, supernova nucleosynthesis, and gravitational-wave observations.


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Tuesday April 18, 2023
Dr. Ismael García Bernete
University of Oxford

Abstract

 

Nowadays, it is widely accepted that most galaxies undergo an active phase in their evolution. The impact of the energy released by active galactic nuclei (AGN) in the interstellar medium (ISM) of the host galaxy has been proposed as a key mechanism responsible for regulating star formation (SF). The mid-infrared (IR) is the ideal spectral range to investigate the nuclear/circumnuclear regions of AGN since dust extinction is significantly lower compared to the visible range. Furthermore, it provides unique tracers to study the AGN-SF connection such as H2 rotational lines, fine structure lines and Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are also a powerful tool to characterize the ISM in different environments.

Recently, we presented new JWST/MIRI MRS spectroscopy of three Seyfert AGN in which we compare their nuclear PAH emission with that of star-forming regions. This study represents the first of its kind to use sub-arcsecond angular resolution data of local luminous Seyferts (Lbol > 10^44.5 erg/s) with a wide wavelength coverage (4.9-28.1 μm). Our results showed that a suite of PAH features is present in the innermost parts of these Seyfert galaxies. We found that the nuclear regions of AGN lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. Furthermore, we find that the nuclear PAH emission mainly originates in neutral PAHs while, in contrast, PAH emission originating in the star forming regions favours small ionised PAH grains. Therefore, our results provide evidence that the AGN have a significant impact on the ionization state and size of the PAH grains on scales of ~142-245 pc. This is fundamental since PAH bands are routinely used to measure star-formation activity in near and far SF and active galaxies.

Finally, I will summarise our ongoing JWST work within the GATOS (Galactic Activity, Torus and Outflow Survey) collaboration. In particular, I will focus on our recent study about the survival of PAH molecules in AGN-driven outflows.


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Thursday April 13, 2023
Prof. Jocelyn Bell
Oxford University

Abstract


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Tuesday April 11, 2023
Dr. Amirnezam Amiri
University of Florence and INAF-Arcetri - Italy

Abstract

 

The abundance of chemical elements across cosmic time provide unique information on the physical processes driving the evolution of galaxies. Current methods for measuring gas-phase metallicities, based on either direct measurements of electron temperature (Te) or calibrations from strong nebular emission line ratios, are based on simplifying assumptions and do not adequately describe the complexity of the emitting regions. We present a new approach based on fitting galaxy spectra with multi-cloud photoionisation models. Unlike current methods, based on comparisons with single-cloud models, our methodology is able to reproduce all observed emission lines to a very high accuracy, down to a few percent, thus allowing for accurate metallicity measurements. We further recover the well known trends between ionization parameter and metallicity, and between the Nitrogen and Oxygen abundances. Our models accurately reproduce the auroral-to-nebular line ratios, while the results of the standard Tmethod are sometimes very different from the best-fitting model metallity. We finally present newly calibrated metallicity estimators for galaxies based on ratios between strong emission lines.

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Friday March 31, 2023
Fernando Merlos García
Instituto de Astrofísica de Canarias / EST

Abstract

El Telescopio Solar Europeo (EST), de clase cuatro metros, es un proyecto que se encuentra en su fase de diseño preliminar, previa a la fase de construcción. Con él se pretende aunar y mejorar las prestaciones de los actuales telescopios solares de clase un metro que están operativos. Uno de los principales objetivos en esta fase del proyecto es poder identificar, definir y gestionar los requisitos de cada una de sus disciplinas organizadas en los distintos paquetes de trabajo definidos. En esta charla se pretende mostrar las herramientas utilizadas para llevar a cabo esta importante tarea.

Youtube

https://youtube.com/live/31KKPdG96LI?feature=share


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Thursday March 30, 2023
Dr. Noel Castro Segura
University of Southampton

Abstract

 

Disc winds and jets are ubiquitous among accreting systems on all scales, from active galactic nuclei (AGN) down to young stellar objects. They represent a key mechanism through which these systems interact with their environment (“feedback") and may be responsible for triggering the mysterious state changes observed in X-ray binary stars (XRBs).

Transient low-mass X-ray binaries (LMXBs), harbouring a black hole or a neutron star, provide us with a natural laboratory for studying the connection(s) between accretion discs, jets and winds.  These systems undergo outbursts, during which they brighten dramatically across the whole electromagnetic spectrum. The outbursts typically last hundreds of days, recur on timescales of decades, and reflect a sudden increase in the accretion rate onto the compact object. Over the course of an outburst, LMXBs exhibit two distinct spectral states. These spectral states are thought to be a consequence of different accretion geometries close to the central object.

Remarkably, the two distinct accretion states also appear to produce two distinct types of outflows. Steady compact radio jets are only seen in the hard state, whereas evidence of disc winds originally came in the form of blue-shifted X-ray absorption lines associated with Fe ions detected only during the soft state. However, recent observations of disc winds in the far-UV, optical and NIR lines reveal a multiphase nature of these outflows that may be present across the entire outburst.  

I will discuss the current status of disc winds in LMXBs with special emphasis in the latest results from far-UV spectroscopy obtained with the Hubble Space Telescope.

 

 

Zoom: https://rediris.zoom.us/j/86826646040?pwd=UmpEZmdKYW90QUpVelFKZitzTzhKUT09
Meeting ID: 868 2664 6040
Passcode: 610738

 

Youtube: https://youtube.com/live/4-WXSHynTXw?feature=share