Recent Talks

Strongly lensed supernovae are extremely rare and powerful probes that can give insights into high-redshift supernova physics, substructures in massive galaxies, and the expansion rate of the Universe. Currently, the lensed supernova field is at a turning point, as we will go from a handful of present discoveries to several hundreds per year with the advance of the next generation of telescopes. In this talk, I will present the current state of the lensed supernova field and future developments. Beginning with the discovery story of ‘SN Zwicky’, a lensed type Ia supernova found with the Zwicky Transient Facility, I will take you on a visual journey, using beautiful observations to highlight our discoveries about SN Zwicky, its exceptionally light lens galaxy, and implications for stellar microlensing. Finally, we will look ahead at the upcoming Vera Rubin Observatory and how it will help us discover more lensed supernovae and refine our understanding of the Universe’s expansion.

The nature and origin of sub-Neptune-sized planets is arguably the hottest debate in the field of exoplanets nowadays. While absent in the Solar System, they are the most common planet type in the Galaxy. Multiple models (gas dwarfs, water worlds, Hycean planets) appear to explain current observational evidence from mass-radius measurements and demographic analyses. JWST promises to break those degeneracies, but the first results are just getting published. In this talk, I will give an overview of the questions surrounding the origin of the "Radius gap", recent discoveries of benchmark sub-Neptune systems, new developments on the modelling of the internal structure of these planets, and how the ERC-funded project "THIRSTEE" aims to answer the questions surrounding this ubiquitous but mysterious population.

La fabricación aditiva (AM) engloba un conjunto de tecnologías que permiten pasar de un modelo 3D a componentes fabricados, creándolos capa a capa hasta completar la pieza. Entre las ventajas de la AM, las que más se aplican a la instrumentación astronómica son la complejidad y consolidación de las piezas, la adición de funcionalidades, la libertad de diseño y la capacidad de aligerado. El objetivo de esta charla es presentar todo el proceso de obtención de prototipos de espejos metálicos (y cerámicos) desde el inicio: desde el diseño conceptual, hasta los tests sobre las probetas de espejos aligerados.

Relativistic jets are amongst the most important and powerful phenomena in astrophysics, and yet also amongst the least understood. Most well known in the context of supermassive black holes in active galactic nuclei (AGN), relativistic jets are also the underlying mechanism behind gamma-ray bursts (GRBs) and LIGO neutron star merger afterglows, and a fundamental component of Tidal Disruption Events. Stellar mass (<20 solar masses) black holes and neutron stars in binary systems, known as 'X-ray binaries' (XRBs), are the local, lower-mass, and hence faster-evolving analogues to AGN, as well as being the direct descendants of GRBs and on the same mass scale as the LIGO merging BH. The near scale-independence of accretion and jet formation with BH mass, theoretically expected and observationally established, demonstrates that what we learn from XRBs can be applied to more massive systems such as AGN. In the past 6 years observations with the MeerKAT telescope have revolutionised our understanding of these jets, allowing unprecedented investigations into the power of black hole jets, measured as we track them decelerating and transferring their launch kinetic energy to the ambient ISM. These observations have also increased our sample size sufficiently that we can now make definitive statements about the relation between jet speed, jet precession, the nature of the compact object, and the connection to black hole spin.

Mass-loss of massive stars is an uncertain, but very important part of stellar evolution, as massive stars lose a significant amount of mass even in their main sequence. Currently, stellar evolution models often include mass-loss in the form of a mass-loss prescription based on the Vink et al. 2001 models. This prescription includes a steep increase in mass-loss for stars cooler than 25000K referred to as the bi-stability jump. The existence of this jump has been contentious for a long time, with multiple observational studies searching for the jump. However, it has never been observed when studying a sample of stars crossing this temperature regime, recently this includes studies with a very large sample size such as the IACOB project. Due to a degeneracy between the clumping behaviour of the wind and the mass-loss rate when looking at optical spectral lines only, it is not possible to measure exact mass-loss rates, but instead you obtain a mass-loss rate convolved with the clumping factor. Thanks to the ULLYSES program and the Xshoot-u optical follow up we now have a sample of B-giants in the LMC and SMC for which we have both optical and UV spectroscopy. UV spectroscopy not only gives us access to important wind diagnostics such as terminal wind speed, but also gives us the ability to determine clumping properties independent from mass-loss rates. The increased complexity we need to include in our models to represent the clumping behaviour does increase the number of free parameters significantly. I will show how we use Genetic Algorithms to fit many parameters at the same time and how we used this method to derive mass-loss rates and clumping properties for LMC and SMC B-supergiants covering the bi-stability jump.

The Atacama Large Millimetre/submillimetre Array (ALMA), the world's most powerful radio facility, is embarking on its most ambitious upgrade since its conception: the Wideband Sensitivity Upgrade (WSU). The WSU consists of an increase of the instantaneous spectral bandwidth by up to a factor of four, while retaining full spectral resolution over the full bandwidth. In addition, an upgrade of the full signal chain will translate in increases in sensitivity. In this talk, I will discuss the major scientific discoveries made with ALMA during the 10+ years of operations, I will present the WSU and its challenges and will conclude with the science that will be enabled once the WSU is delivered.

The instrumentation for gamma-ray astronomy has advanced tremendously during the last two decades. The study of the most violent environments in the Universe has opened a new window to understand the frontier of physics, exploring processes that are beyond the capabilities of Earth-based laboratories to replicate. In this talk, I will review the different strategies and instrumentation for gamma-ray astronomy, and report some of the most exciting observations from this rapidly evolving field. Among all instruments, the talk will be somewhat biased towards scientific results obtained with MAGIC, which is located on the Canary Island of La Palma, and has been at the forefront of gamma-ray astronomy since 2003, participating in multiple multiwavelength and multimessenger observational campaigns.

Canon is using its in-house ultra-precision cutting machines to provide the market with new optical devices for spectroscopy, including the world's first CdZnTe and InP immersion gratings and IFUs. They are used in the VLT and ELT instruments of Europe/ESO and in the instruments of the US/KECK and DKIST. The advantage of high-precision cutting is that surface roughness of less than 1 nm RMS can be obtained by cutting alone, so if the shape can be fabricated by cutting, it becomes an optical device. Since no post-processing such as polishing is required, optical devices with fine and sharp structures can be fabricated, and machined image slicers are a major advance in IFUs.
In my presentation, I will introduce the performance of our original cutting machine and the devices we have fabricated.

Segunda tanda de las charlas de instrumentación de los becarios de verano.

Supermassive black holes (SMBHs) in Active Galactic Nuclei (AGN) play a key role in the formation of galaxies and large-scale structure, but the triggering and impact of AGN feedback across scales and the origin of the observed SMBH–galaxy connection remain major open questions owing to the multi-scale and multi-physics nature of the problem. AGN feedback can also profoundly affect the properties and spatial distribution of baryons on scales that contain a large amount of cosmological information.  Current and upcoming cosmological surveys will provide unprecedented data to constrain the fundamental cosmological parameters, but uncertainties in galaxy formation physics remain a major theoretical obstacle to extract information from cosmological experiments.  In this talk, I will present new simulation techniques that are pushing the frontiers of galaxy formation modeling towards (1) the smallest scales, developing physically predictive models of SMBH accretion and feedback explicitly at sub-pc resolution in a full cosmological context and (2) the largest scales, using thousands of large-volume simulations exploring a wide range of sub-grid feedback implementations to train machine learning algorithms that can maximize the extraction of information from cosmological surveys while marginalizing over uncertainties in galaxy formation physics.  I will demonstrate the feasibility of these orthogonal approaches to address fundamental problems and discuss their potential to advance the fields of galaxy evolution and cosmology.

Zoom link: https://rediris.zoom.us/j/95949230133?pwd=xxXArEDCwNg4iXt4f5vUiCGvUFC9ph.1